GiS Survey

GPS - Global Navigation, Something for Everyone

ohmara.rain@gmail.com — Fri, 03 Oct 2008 17:39:00 +0000

By: stowaway

In this day and age traveling by map is getting to the point where theglove box is full of them and folding them back into there properposition is a pain. Plus the majority of people I know can't even readone.

This is where the high-tech GPS units come in today's life. There aremore than 24 GPS satelites that orbit around Earth that put out timingsignals by radio. This allows any GPS unit to accuratly determine itsLongitude, Latitude, Altitude, time and speed anywhere on Earth.

The GPS wasn't available to civilians until recently. It was originallynamed NAVSTAR GPS and was developed by the United States Department ofDefense which launched the first experimental satalite in 1978.

Today the GPS is accurate to as close as a 1ft. making navigating to anexact point easy. With todays GPS units available for Vehicles, Boats,Planes, Helicoptors, Tanks and portable Handhelds you can go anywherewith one.

There are many different uses for GPS systems. I mainly use one forboat navigation. Traveling 50-100 miles offshore with just a compasscan get downright scary once you look back and land is nowhere to beseen. A friend of mine is a hunter and he likes to walk upto 5 milesinto the forest. Without a GPS he'd never get back to his truck. Mywife has one in her car, she puts in an address and it will give you thebest directions to that address. It even tells her when she's passedher turn and recalculates a new direction to get her where she needs togo. It is truely a wonderful thing to have and can help the directionilliterate's get anywhere they need to go.

Article Source: http://www.a1-articledirectory.com

What is GPS and how can it be used?

ohmara.rain@gmail.com — Fri, 03 Oct 2008 16:23:00 +0000

By: Angie Carter

GPS stands for Global Positioning System and was initially designed to be used by the U.S.military and is operated by the U.S. Defense Department. This system consists of 24 satellites, these satellites are 12,000 miles above us, are constantly moving in a precise orbit, have an atomic clock, and are solar powered. They do have a battery backup so they will continue to run in the event of a solar eclipse, and each satellites has a small rocket booster to maintain their orbit. The first satellite was launched in 1978 and it wasn’t until 1994 when there were a total of 24 satellites. Each satellite has a life expectancy of about 10 years, so new satellites are constantly being built and launched. Each satellite weighs about 2,000 pounds and is approximately 17 feet in width when the solar panels are extended. In the 1980s the GPS became available to the public, and although it is still maintain by the U.S. Defense Department there is no charge for its usage by the public.

These 24 satellites orbit the earth twice a day and continuously sends the location of the satellite. A GPS system can tell how far a satellite is away by comparing the time difference between the time a signal was transmitted and the time it was received, the longer it takes the signal to be received by a receiver, the farther away the satellite is. If a GPS is receiving signals from three satellites it can calculate latitude and longitude. Altitude can be determined if the GPS is receiving signals from four satellites.

GPS can be used for navigating your car through traffic day-to-day or tracking a fleet of vehicles. Not only can a driver use a GPS for directions the main office knows where that vehicle is and the speed of the vehicle. GPS can be used while on vacation for activities such as hiking, camping, or hunting. Is your passion fishing but get frustrated trying to find the fish? With a fish finder which uses both GPS technology and sonar you’ll know exactly where to go to find those fish. GPS technology is also being used as a way to track your pet if he wanders off or to safeguard a pet from being stolen.

Another use for GPS is as a child finder with a receiver in a child’s cell phone or wristwatch to ensure a child’s safety. It can be used in a teenager’s car in order to both know where they and how fast they are driving. This could also be used to keep track of someone who tends to ‘roam’ but is not capable enough to find there way back; i.e. someone with Alzheimer’s disease.

As GPS technology improves, it uses will increase. Who knows where it will take us next?

Article Source: http://www.a1-articledirectory.com

Tip - Microsoft Pro Photo Tools 2 for geotagging photos

ohmara.rain@gmail.com — Tue, 30 Sep 2008 19:32:00 +0000

By GISuser

Microsoft Pro Photo Tools provides a set of tools for photographers to perform various tasks with their images—including RAW captures. The current version enables you to quickly geotag your photos, view and edit metadata, and more, leveraging the power of Windows and Microsoft Live Local.

New in Microsoft Pro Photo Tools 2
* Support for reading and writing metadata to/from XMP side cars so that metadata will interoperate with Adobe products. This is in addition to reading and writing from the file.

* Users can convert from RAW to JPEG, TIFF, and HD Photo using "As Shot" settings. This includes the ability to resize the image.

* Users can view actual RAW image in addition to thumbnails

* Support for 64-bit Windows

* Support for international locales

* Improved UI for geotagging

Pro Photo Tools includes the following features:

Geotagging with flexibility

As geotagging gains popularity, photographers want to be able to quickly identify the location for their images. With Pro Photo Tools, you can gather location information from a variety of sources and apply it to the metadata in your images.

Screenshot of thumbnails tab in Microsoft Pro Photo Tools.

Determine location name automatically

With Pro Photo Tools, you can automatically apply the actual name of the location where a photo was taken based on the GPS coordinates. Instead of numbers, you'll have the "real" names, and that information can then be saved in the metadata for your photos.

Determine GPS coordinates from location name

Just because you haven't always had a GPS receiver doesn't mean you can't assign GPS coordinates to your photos. In fact, using the power of Microsoft Live Local you can determine the GPS coordinates where any photo was taken based on location name information in the image metadata. The GPS coordinates can then be added to the metadata for your photos and the photos plotted on a map.

Identify location on a map

For the maximum in flexibility when assigning a location to an image, you can navigate to the precise location where you took a given photo and tag the photo with that location information based on a specific position on the map.

View images on a map

As cool as it is to have GPS coordinate information connected to your images, to really get a sense of place with your photos, you need to view them on a map. Pro Photo Tools utilizes Windows Live Local to display your images on a map of the world, including the ability to view your images on a normal map or a satellite view of the world.

Edit image metadata

Metadata has become increasingly important to photographers as a way to manage and organize their images. Among the many things it enables is a rich capability to search for images. You can now update a wide range of metadata for your images using Pro Photo Tools, and that metadata gets stored in the actual image file, so wherever your photo goes, your data goes.

RAW support

By leveraging the Windows Imaging Components (WIC), we're able to provide support for any RAW file format (in addition to TIFF and JPEG) for which a codec has been developed. And that includes most RAW file formats. Not only can you view your RAW images within Pro Photo Tools, you can also update metadata—including GPS coordinates—directly in the file. The updated metadata is stored within the RAW file, not in a cumbersome "sidecar" file. (For information on obtaining codecs for your RAW images or other file formats, visit Codecs for Windows.

Article source : http://www.gisuser.com/content/view/15689/2/
Written by GISuser Monday, 29 September 2008

Eight Things You Need to Know About GPS

ohmara.rain@gmail.com — Mon, 29 Sep 2008 21:01:00 +0000

By Matt Rosenberg, About.com

Global Positioning System (GPS) devices can be found everywhere - they're used in cars, boats, airplanes, and even in cellular phones. Handheld GPS receivers are carried by hikers, surveyors, map makers, and others who need to know where they are. Here are the eight most important things you need to know about the GPS.

The Global Positioning System is composed of twenty-four satellites 20,200 km (12,500 miles or 10,900 nautical miles) above the earth. The satellites are spaced in orbit so that at any time a minimum of six satellites will be in view to users anywhere in the world. The satellites continuously broadcast position and time data to users throughout the world.
Using a portable or handheld receiver unit that receives data from the closest satellites, the GPS unit triangulates the data to determine the unit's exact location (typically in latitude and longitude), elevation, speed, and time. This information is available around-the-clock anywhere in the world and is not dependent on weather.
Selective Availability, which made the public Global Positioning System less accurate than the military GPS, was turned off on May 1, 2000. Thus, the GPS unit you can buy over the counter at many retailers is as accurate as those used by the military today.
Many over-the-counter handheld Global Positioning System units contain base maps of a region of the earth but most can be hooked up to a computer to download additional data for specific locales.
GPS was developed in the 1970s by the U.S. Department of Defense so that military units can always know their exact location and the location of other units. The Global Positioning System (GPS) helped the United States win the war in the Persian Gulf in 1991. During Operation Desert Storm, military vehicles relied on the system to navigate across the barren desert at night.
Global Positioning System is free to the world, developed and paid for by U.S. taxpayers through the U.S. Department of Defense.
Nonetheless, the U.S. military maintains the capability to prevent enemy use of GPS.
In 1997, U.S. Secretary of Transportation Federico Pena stated, "Most people don't know what GPS is. Five years from now, Americans won't know how we lived without it." Today, Global Positioning System in included as part of in-vehicle navigation systems and cellular phones. It's taken a few more than five years but I know the rate of Global Positioning System use will continue to explode.

Article source : http://geography.about.com/od/geographictechnology/a/gps.htm

The meaning TRUE actually of Cartography : GIS Data-Editor & GIS Surveyor

ohmara.rain@gmail.com — Sun, 21 Sep 2008 03:36:00 +0000

By Ohmara

The important factor most between the work be the understanding. GIS-Surveyor with GIS-Data-Editor must have the understanding is consistent each very much others , for the work that come out orderly and is correct.

In GIS department might not can specify that how is which faction significant more? Every the faction will must work to accompany with for be born the efficiency.Particularly Surveyor with Data-editor will must base the understanding in work substance and knowledge base in a tool,equipment all equally. Otherwise,it will be difficult work to understand or communicate with.
Data-editor will must to talk with Surveyor to arrive at the data and data detail that want that thoroughly,so that Surveyor to go to still the aim that is correct. Meanwhile surveyor must to explain give with data-editor knows about a problem , and all obstacle of the survey to Data-editor too.
Because , the thing that Data-editor will must do that is data area Serveyor to are person go out store come in. And what is Serveyor that go out to capture , must get know arrive at the substance of the work from Data-editor first.The work in the system of GIS, that can not behave alone get.An everyone must is in the team.The understanding get into trouble important in work life , and what is showwing off one's ability each other don't help to have makes progress.The unity will to separately make to bear fruit the work.
Because , A map in your that hand imply combination story takes many varied things are enterring in paper just one. And that the meaning TRUE actually in the cartography , every things will must total up to become one.
map of the world

Put to the Test

ohmara.rain@gmail.com — Wed, 17 Sep 2008 19:09:00 +0000

By Dana Trethewy

Comparing various grades of GPS receivers shows that while the survey variety is clearly more accurate, mapping units have their place in GIS.

For years, public and private entities have traditionally carried out resource inventory and position tracking projects using hardcopy maps and other manual techniques. As GPS technology has become more widely available and cost effective, agencies have adopted mapping-grade technology for resource inventory, management, and other activities.

Today, most entities use mapping-grade GPS for data collection and storing this information in geographic information systems (GIS), which can range from single analyst to enterprise-level multi-user environments. Many mapping-grade GPS users employ differential correction through post-processing to remove errors from the GPS data and produce more accurate results. However, the adoption of real-time differential correction has yet to gain widespread use by mapping-grade GPS users.

Why this historic overview? It sets the stage for our side-by-side test. Marshall and Associates (Marshall) and partner Bush, Roed, & Hitchings (BRH), a civil engineering and land surveying firm in Seattle, Washington, are conducting a small, ongoing, unscientific study near Green Lake Park in Seattle to compare GPS receiver grades and DGPS correction methods typically used by surveyors. The various GPS receivers include survey-, mapping-, and recreational-grade units. The evaluated DGPS methods focus on real-time correction and include the WAAS (Wide Area Augmentation System) and VRS (Virtual Reference Station) correction from the WSRN (Washington State Reference Network). Marshall has used mapping- and recreational-grade equipment and BRH survey-grade GPS receivers to collect location data for approximately 20 deciduous trees.

Article source : PROFESSIONAL SURVEYOR MAGAZINE ONLINE (http://www.profsurv.com/)

The Lost Maps of Nagaland

ohmara.rain@gmail.com — Tue, 16 Sep 2008 08:44:00 +0000

By Dave Smith

The Times of India brings a story, speaking to the necessity of preserving maps and records dealing with boundaries - apparently the official maps depicting the boundary of the Indian state of Nagaland have gone completely missing.

Nagaland is a hill state in the foothills of the Himalayas, located in the far northeast of India, adjoining the Indian states of Assam, Arunachal Pradesh and Manipur, and bordering Myanmar (formerly Burma) to the east.

From the article,

The government has lost all "original documents" — comprising details of boundaries — of Nagaland, in a glaring instance of callous handling of vital public documents.
The Union home ministry and the Assam government, which originally kept the records of Nagaland, do not even have the valid "map" of the state which ironically is in the throes of violence sparked by the demand to carve out Greater Nagaland by extending the existing boundaries of the state.
The matter came as a shock to home ministry officials when it was brought to light for the first time by Nagaland during its submission before the Local Commission on the Assam-Nagaland Border here last week.
In response to the commission's direction to submit before it the original documents of the state to settle boundary disputes, Nagaland said it was not in a position to give the written statement unless "its original documents which were purportedly lost by Assam" were returned.

At present, it looks like some of the details of the boundary will have to be recreated from surveys and whatever remaining documentation can be salvaged. The region has not been without its share of historic boundary disputes.

Article source: http://surveying-mapping-gis.blogspot.com

Wednesday, September 10, 2008 at 6:58 PM by Dave Smith

GiS Worker of the month: September 2008

ohmara.rain@gmail.com — Mon, 15 Sep 2008 12:42:00 +0000

In this month. We much to be proud of two GiS's worker to introduced. One is a chairman in America. And another one is a serveyor & data-operator in Thailand.

David G. Smith

Age: 42
Gender: Male

Astrological Sign: Cancer
Zodiac Year: Horse
Industry: Technology
Occupation: Surveying / Mapping / Engineering / GIS
Location: Scranton : Pennsylvania : United States

Currently: Vice-President and Director of Geospatial Information Technology for Synergist Technology Group, Inc.

Jakkapong Tongsomboon.

Age: 26
Gender: Male

Occupation: Surveying / Data-Map / GIS
Location: Donmung : Bangkok : Thailand

Currently: Works at Total Water Co.,Ltd.

View in more images and information of them from column "About work?"at Inside GiS Survey.

Epic Battles: GIS vs. Surveying?

ohmara.rain@gmail.com — Sun, 14 Sep 2008 22:40:00 +0000

By Dave Smith

Discussion revolving around a planned, but retracted article on GIS for Professional Surveyor Magazine has led to a lot of interesting discussion, but to me generally reveals a continuing underlying tension and misperceptions between the GIS and Surveying communities.

Adena Schutzberg / All Points Bulletin: Update: State Licensing Board "Censors" GIS Article
James Fee / Spatially Adjusted: "GIS Practitioners as Doing Work Surveyors Should Be Doing"

While these articles post updates and amendments, based on comments by Tom Gibson, Professional Surveyor's editor, which clarifies that the author decided to retract his article, the underlying question of GIS versus surveying and legal jurisdictions still remains.

Some of the comments are telling - with perceptions and suggestions that State Licensing Boards are somehow cracking down in draconian fashion, demanding censorship and attacking GIS practitioners. Tied into this, we had the MAPPS lawsuit (another issue which I believe will resurface at some point), overlap of surveying with photogrammetry, and other issues. Meanwhile, in the surveying community, we still hear "GIS = Get It Surveyed".

I have my own, perhaps unique perspectives and insights, being a GIS practitioner since the late 1980s, as well as a licensed Land Surveyor, and finally, also serving as chair to a State Licensing Board.

Note: Having said this, please note that my comments to follow are my own personal views, and are not to be taken as official statements or in any way representative of our State Licensing Board's.

For most GIS practitioners, they readily defer to surveyors' knowledge and domain expertise on cadastral issues - matters of how property boundaries are properly dealt with, and so on - and similarly, most surveyors know their limitations when it comes to GIS. However, there still seems to be occasions which give rise to confusion and misperception.

One basic thing that we all need to come into reckoning with is that Surveying and GIS overlap, but that neither is wholly contained within the other, and that each has areas which may additionally be mutually exclusive from the other. Another part of this Venn diagram equation is Photogrammetry - another topic, which has come up often. I have best seen it illustrated as such:

One area of contention is that some states' Practice Acts are very broad in their definition of what constitutes land surveying - e.g. "measurement and determination of any feature on the earth's surface" - which might not be appropriate for the strictest of interpretations. Many everyday GIS efforts could constitute surveying practice under this definition - but is it appropriate?

If one considers typical State laws pertaining to licensure and practice of land surveying, one will see that the primary objective is in protecting the public, it has little to do with protecting the surveying profession.

So what is falls within the purview of licensing boards, and what falls within the definition of land surveying, toward preventing harm? That may vary somewhat from state to state.

But how might the public be harmed by GIS data, as opposed to proper land surveys? Here are some generalized versions of recent tales I've heard:

A county tax mapping office, where a GIS practitioner "helps" a realtor friend in a bind by preparing a property description based on lot lines in the GIS. Where did those lot lines come from? Combination of digitized paper maps, lines rubbersheeted to apparent fencelines on orthophotos, and so on. The harm? This description brings with it apparent legal connotation, as a representation of lines of ownership. The buyer may be getting a misrepresentation of what the lot's actual extent and location is.
A municipality orders a homeowner to demolish and remove a brand new addition, based on their perception that it is in violation of setback lines - based on the GIS.

These things can be only be remedied through a proper survey. One definite question that should be asked, is whether litigation or legal action might ever be a possibility. If it's anything relating to or impacting property ownership and use, such as property boundaries, rights-of-way, easements, or things of that nature, one would definitely want reliable, accurate survey data that can hold up in a court of law. Most county GIS systems will not pass this test.

Perhaps there a jurisdictional issue at stake, such as wetlands delineation (where US EPA, Army Corps of Engineers, State Environmental Protection Agencies or others may or may not have jurisdiction, based on whether or not the land in question is a wetlands or not). Given an instance where a wetland may have been filled, drained, or otherwise encroached upon, and where the original physical evidence of plants, hydric soils, and wetlands flags may no longer exist, a surveyor's location of and ties to the wetland biologists' flags is far more likely to hold up to scrutiny, be accurately retraceable in the field, and be defensible in court than GIS data from recreational-grade GPS receivers or other approaches that are occasionally seen in use.

Or a toxic waste spill - whether it impacted adjoining properties or not - and so on. The same circumstance may come into play with other jurisdictional issues, such as taxation and municipal jurisdiction, and other areas.

Is it a specific legal requirement that these types of data be collected by surveyors in these cases? To turn that question around, in these cases it's instead a matter of basic good practice and adequate protection from dispute and liability as to how the locational data is captured.

Not every GIS practitioner has to deal with these things - but some do very much need to be cognizant of it. And certainly GIS practitioners do need to be aware of state Land Surveying Practice Acts in any regard. Ambiguities will not be resolved overnight - certainly questions of "what DOES that cadastral GIS system really represent" will continue to come up again and again. And certainly many stewards of cadastral GIS are aware of this, and put as many protections in place as they are able to - such as disclaimers and metadata, but for most citizens and casual users of the data, the phrase "consult the metadata" will only lead to glazed eyes. And while GIS systems are fully able to accomodate survey-grade data, and while some nations have made great strides toward a coordinated cadastre, here in the United States, the approach has been far more piecemeal, with varying degrees of robustness in how cadastral data can be improved. I have suggested record-level metadata for parcel data and similar approaches to allow refinement, where good, vetted, survey-grade locational data can be utilized and held toward iterative acquisition of a uniformly high-quality database. The locational accuracy of each parcel and subdivision can then be assessed on a case-by-case basis. Additionally, database linkages to plats and other survey data can be put in place.

Certainly not easy questions to answer overnight - but also hopefully I can share more insight and reality than perceptions that "Surveyors are trying to take over GIS".

Article source on: Saturday, July 05,2008 at 11:15 AM by Dave Smith

A Compendium of State Land Surveying Practice Acts

To follow on to my previous post, "Epic Battles: GIS versus Land Surveying?" I have compiled this list of Land Surveying Practice Acts. These are state laws, which govern the practice of land surveying within each jurisdiction, and which define what each jurisdiction views as work to be performed by licensed land surveyors. (Link to : List of Land Surveying Practice Acts.)

Article source on: Sunday,July 06,2008 at 6:37 PM by Dave Smith

Please see full article at: http://surveying-mapping-gis.blogspot.com/

GIS in the Real World: A Primer for Newcomers

ohmara.rain@gmail.com — Fri, 12 Sep 2008 15:12:00 +0000

Article from US Census Bureau

This column addresses questions from newcomers to GIS. Students who spend hours sitting in class, working on allocation problems or digitizing datasets often graduate with no idea which industries use GIS, computer-aided design, desktop mapping and Global Positioning System technology, nor how these technologies are used. Questions arise about GIS in the "real world."
I've taken GIS courses and want to work with GIS. What kinds of opportunities are available for me?
Many occupations today use GIS as a tool for anything from resource allocation to market analysis. Geographers' opportunities continue to grow as different industries find GIS applications an integral part of the job. For example, the Middle Atlantic Division of the Association of American Geographers recently sponsored a Career Day that featured speakers from local, state and federal government agencies and private firms. Students who attend events such as these can gain some perspective on career opportunities and meet practitioners and potential employers.
Susan Jampoler of GeoKnowledge Inc., Leesburg, Va., identified many growing fields that offer roles for geographers who can apply their solid knowledge of spatial systems and geographic theory to areas such as banking, marketing, advertising, insurance, emergency management, health care, forestry, agribusiness, real estate, economic development, telecommunications, hazardous waste management and sales. You also might benefit from additional coursework related to the field; for example, business courses might help if you wish to work in advertising or marketing.
Will I have to digitize all day?
Building a spatial database can be the most expensive and time-consuming part of any project. For this reason, GIS professionals can spend much of their time digitizing, manipulating and correcting a database, but this isn't always the case. Some companies are information gatherers that build datasets for use by others. As an information analyst with such a company, your job might consist of data collection, verification and documentation. You'd also spend time providing customers the geographic knowledge they need to best use the datasets. Private companies and government agencies at all levels play a major role in creating datasets.
How would you spend your time if you worked for a company that uses datasets collected by others? Suppose you're a computer-aided design manager with an environmental engineering firm. Some of your time would include customizing datasets obtained from county agencies. You'd then use the datasets to produce maps for various engineering projects at the firm and for business development and marketing presentations. In this type of position, you'd also devote time to researching current hardware and software and recommending purchases.
Perhaps you want to work on the other side of the fence and develop software. As a member of the technical staff at a large GIS services firm, you might work closely with clients to design custom interfaces, provide software training and write data translators. You also might perform systems administration, GIS network and database design and application design. Such jobs require extensive computer skills, including programming in various languages, relational database knowledge, software engineering, and object-oriented and procedural design theory-in addition to applied geographic training.
How can I find out more about career options?
Excellent resources abound for discovering what people do with GIS. First, read some of the magazines devoted to tracking GIS trends. These are packed with articles written by people in different fields that describe projects, partnerships and technology.
Online bulletin boards and newsgroups such as comp.infosystems.gis also provide insight to GIS in the real world. Every day people discuss online resource and data needs, software and hardware, research topics, education programs and myriad other tasks. Of course you'll also find many position announcements that can give you an idea of skills sought by employers.
Finally, get out and talk to people. Yes, network. Attend conventions, workshops, career days, professional association meetings, federal open houses or any other such gathering. Networking is like investing-it's never too early to start!
Article source : http://careers.geocomm.com/resources/censusjobfaq.html

GPS Software for GIS and Surveying

ohmara.rain@gmail.com — Wed, 10 Sep 2008 06:44:00 +0000

GPS units continue to drop in price and size, new software features give users more power, and Pocket PC's take the show on the road.
by Kyle Bohnenstiehl
Introduction
The Global Positioning System (GPS) has become an essential tool for GIS database developers and users over the last 10 years. GPS hardware is portable, relatively easy to use, and can locate features to within several millimeters using sophisticated software, to about 1m using resource grade differential correction software/hardware or to within 10 meters autonomously using hand held units. GPS software falls into two main categories: survey grade software for network (least squares) adjustment of GPS points, and GIS mapping software that produces GIS ready files containing features, attributes and differentially corrected position information. A third software category runs on Pocket PC platforms with low-cost handheld or PCMCIA GPS instruments.
A new component has been added to the GPS constellation recently and is worth looking at: the Wide Area Augmentation Service (WAAS) managed by Ratheon Inc. Trimble Navigation has also produced a WAAS PDF brochure. This is a satellite broadcast signal that increases GPS accuracy to about 5-7m, is free, and works with most GPS units manufactured after January 2001. It was developed by the FAA to increase aircraft navigation accuracy but works poorly in forest canopy and obstructed areas.
OEM GPS Hardware and Software
A GPS instrument is a rather unsophisticated piece of hardware by itself. Several manufacturers make and sell OEM GPS chips/pucks/mouselike devices with interface cables that are capable of taking input from a GPS antenna and returning a NMEA ASCII string of Latitude/Longitude/HAE (in WGS84) and the precise UTC time. Cell and satellite phones with GPS chips use this information to return the location of the phone to central call centers to route calls more efficiently, dispatch emergency services, or deny service to/from unlicensed countries. These single frequency (L1/CA code) OEM GPS chips cost upwards of $20 and even the more sophisticated dual frequency (L1/L2) chips are relatively inexpensive. GPS manufacturers add value to their products by designing sophisticated GPS receiver interfaces, antennae systems, and PC software to process raw GPS data into GIS data and surveyed points. Recently, GPS Compact Flash cards with integrated antennas and power supplies have become available.
Very Accurate Systems
Survey grade instruments are defined as GPS units that collect data using both L1 and L2 carrier phase data with a sophisticated antennae mounted on a tripod or other fixed mount for static observations. These units can also go mobile and collect L1/L2 data on the fly using kinematic observations. Generally, GIS data capture is cumbersome with survey type systems and attributing is difficult. Real Time Kinematic (RTK) systems do allow users to collect point, line and polygon GIS data to a high degree of accuracy (+/- 2cm XYZ potentially) and some companies have good data logger interfaces to allow attribution of features. It is possible to link RTK systems to other dataloggers like Trimble's ASPEN software on a pen based notebook PC. However, the ability to collect GIS features using RTK GPS technology is still limited.
Survey grade systems rely on very sophisticated software programs to process data to centimeter level accuracy. GPS data from several known points is processed with simultaneously with GPS data from at least one unknown point. The GPS data files must overlap in time and hopefully use the same constellation of satellites. A vector is calculated (delta X, delta Y, delta Z) from each point in the network to every other point in the network. These baselines are then put into a network adjustment package to create a best fit solution. The resulting coordinates of the previously unknown points will have a set of statistics associated with them that is an excellent indicator of the absolute accuracy of the position.

Figure 1: Screen shot of Trimble Navigation's Geomatic Office software.

Good Enough for GIS?
So-called resource grade systems are GPS receivers (and software) that allow users to collect GIS data with GPS at an accuracy of 0.50m (differentially corrected) and to about 10m (autonomous). Detailed data dictionaries are a part of the data logger software and the post processing software allows for editing of topology and attributes and the display of background GIS data and imagery. This type of GPS system has to have a datalogger front end for GIS data collection. The TSC1 from Trimble Navigation, a variety of products from Corvallis Microtechnology, and the Leica GS50 do this with a ruggedized solution . All of these products have both a field software (firmware) and an office software module for differential correction and GIS data export.
Trimble Navigation has developed a very mature product called PathFinder Office which allows for sophisticated differential processing and GIS feature manipulation. Sub-meter accuracy can be obtained with phase processing and the program can even automatically batch process your data and create the proper GIS output file. The software will go to the internet to find suitable base station data and request the proper times and dates. The best feature of this class of software is the ability to create detailed data dictionaries for GIS features. Overall, this type of software and hardware solution is still the best system for most GIS users given the flexibility and control it affords. A series of screenshot images offer some insight into the sophistication of the software.
Figure 2: The data dictionary editor allows for the creation of GIS point, line and polygon features with many attribute types and is fully customizable.

Figure 3: Maps showing the different features collected with the GPS can be generated.
Figure 4: Pfinder Office will go out to the Internet and download GPS base station data from the closest GPS base station, in this case Pie Town, NM CORS station.
Figure 5: After differential processing and filtering, editing of attributes and topology, you can export the GPS data out in many different GIS and CAD formats.
Another interesting data collection system is the Red Hen Media Mapper which integrates a GPS position, a digital picture or video clip, and the Red Hen software to create "multimedia GIS files". The software will export MapInfo or ArcView files that have features with hotlinks to the digital image files.
Low Cost, High Stress GPS for GIS
The least expensive GPS hardware is the recreational GPS receiver. These units are small and very portable but can only collect point feature data easily. Attribution is limited to one or two fields (name and type of landmark for example) and the elevation may or may not be recorded, depending on the model. There is a wide variety of free and low cost software packages on the market, although very few can generate GIS compatible files directly (in the DXF format with one or two attribute tags, usually no elevation information). A comprehensive set of software links is provided here (scroll down the page to 3rd Party Software) and a good set of ArcView tools can be had from the Minnesota DNR. If you want to create a DXF file from Garmin data try this program. ESRI has posted a user submitted ArcView script to do some Garmin translations. Another good free package is available from TopoGrafix.
Differential corrections with recreational grade GPS are not a routine procedure, but it can be done, resulting in static point accuracy of about 0.50m. If you have a Garmin instrument, you can log the phase data to a laptop in the field by executing a series of commands via a DOS program available here or here. Note that you cannot move the GPS during the data logging which means you will only be able to map points in this manner. Once you have logged sufficient GPS data, you will need to convert it to RINEX (receiver independent exchange) format using a conversion program available from the same two websites. Now you can process the data in any differential corrections software that accepts RINEX files. This would be an excellent example of how one could utilize the CORS NGS GPS base station data. If you are looking for a good differential processing program for a low cost (there are not too many out there) then try this link. This may all seem rather cumbersome but differential corrections with a low cost GPS is a tremendous capability at a cost of around $600 for a GPS unit and the licensed versions of the software.
Topographic Map Viewing
Software On the PC software side of recreational GPS, is a full suite of topographic map viewing software packages. Topographic maps and some proprietary vector file formats can be loaded into the recreational GPS units for display and navigation but no editing is possible. Essentially, for GIS mapping, this capability is not very useful due to the proprietary nature of the files and the limited screen size and resolution. A complete list with software reviews is at the Joe Mehaffey GPS site. These are not GIS programs by any means, but do allow for some good cartography and easy transfer of waypoint, route and track data to and from the GPS. A very recent release on the market is MapTech Terrain Navigator 2001. It performs 2-D and 3-D viewing of topographic maps (see Figure 6) and runs on a laptop or desktop PC and can accept GPS input for real-time tracking (see Figure 7). There is quite a bit of capability in this software, like 3-D anaglyph viewing of topographic maps, powerful route and waypoint editing tools, and a large library of CD map libraries for sale, and good cartographic tools. They also make a product for boat navigation called Digital Chart Kit 2001. This provides some excellent tools for navigators and can even plot bathymetry in 3-D (see Figure 8) and show the boats real-time position. Overall, the MapTech products install and perform flawlessly and are a good value for users needing to plot real-time positions.
Figure 6: MapTech Terrain Navigator: 3-D Drape
Figure 7: MapTech Terrain Navigator Software: GPS connectivity window.
Figure 8: 3-D wire frame of realtime bathymetry.
Palmtop GIS
When the Compaq IPAQ hit the market last year, many people with an interest in mobile mapping took note. This unit and others like it run a Windows CE operating system, can accept a wide variety of expansion and memory cards (including non-differential GPS), and feature dazzling color screens with fast (200+mhz) processors. Sophisticated GIS and CAD software can run on these units and when coupled with a differential GPS through a serial USB connection, a complete mobile mapping solution is at hand. The advantage of a system like this is that a relatively "dumb" and inexpensive GPS unit can be connected to a very sophisticated data logger that can be upgraded and reconfigured with new software as needed. Without a differential GPS connection or GPS post-processing, this system is less useful but certainly has utility for navigation and course plotting.
MapTech has just released its Pocket Navigator software for Windows CE (PocketPC) computers. This software allows you to connect a GPS to a moving map window on the PocketPC and view USGS 7.5', 1:100000, 1:250000 and world maps, NOAA nautical charts, and waypoint and track data. The GPS connects thru a type II PCMCIA slot that that is either built into the PocketPC or is part of a "jacket" that slides onto the back of the PocketPC. Be aware that many of these devices only have one expansion port so additional flash memory and other devices will have to be used one at a time. It is also possible to link bulkier, sometimes less expensive, DGPS enabled recreational or resource grade receivers to the PocketPC via a 9-pin serial to 25-pin serial Pocket PC connector. Essentially, with the MapTech Pocket Navigator, you subset maps from their CD sets, upload them onto your PocketPC, and as you move around outside, a moving map window with a cross hair is displayed. You can add waypoints and routes, and calculate bearings and distances. One drawback to all of the GPS "topographic mapping" software on the market is the impossibility of importing and viewing standard raster and vector GIS data formats. While not the intention of these programs, it would be a nice feature to have.
Full featured GIS/CAD software applications are available for Pocket PCs and when equipped with a GPS, make for very useful tools. Five, well developed products are available and can be recommended. Autodesk makes the On Site software for PocketPCs that allows CAD drawings to be edited and verified in the field. The ArcPad software from ESRI has similar functions and offers most of the vector functionality of ArcView and good support for compressed imagery. The Fieldworker software by Fieldworker Products has GPS and GIS support and allows for the capture of digital pictures. Trimble Navigation has the TerraSync software for PocketPC, which support vector data collection and editing, raster background images, internet maps and imagery, and most importantly carrier phase high accuracy GPS input (when used with compatible Trimble products). Tripod Data Systems (TDS), a leader in field data collection interfaces, offers the Solo CE GPS-GIS data collector system with many of the same features as the Trimble software. This is not a surprise- Trimble acquired TDS in the fall of 2000.
Conclusions
The rapidly changing state of technology in the GPS hardware and software arena will pose some difficult challenges to GIS users. It will be necessary to thoroughly investigate and demo any system you are considering for purchase to make sure it has the right features for your needs. Fortunately, most companies offer demos or are willing to demonstrate the equipment for you so take advantage of this and the support they offer.
Remark : Kyle Bohnenstiehl has been involved in remote sensing, GPS and GIS for over 10 years and is currently a remote sensing scientist with the Department of Interior. His work has taken him throughout the Andes of South America and the desert Southwest where he has worked with tribes, NGO's, government and private sector groups to create innovative solutions using the latest geotechnology. He can be reached at Kyle@nagis.com
Article source : http://www.gisvisionmag.com/software_reviews/gps_full.php

Data representation

ohmara.rain@gmail.com — Tue, 09 Sep 2008 05:04:00 +0000

From Wikipedia, the free encyclopedia

GIS data represents real world objects (roads, land use, elevation) with digital data. Real world objects can be divided into two abstractions: discrete objects (a house) and continuous fields (rain fall amount or elevation). There are two broad methods used to store data in a GIS for both abstractions: Raster and Vector.

Raster
A raster data type is, in essence, any type of digital image. Anyone who is familiar with digital photography will recognize the pixel as the smallest individual unit of an image. A combination of these pixels will create an image, distinct from the commonly used scalable vector graphics which are the basis of the vector model. While a digital image is concerned with the output as representation of reality, in a photograph or art transferred to computer, the raster data type will reflect an abstraction of reality. Aerial photos are one commonly used form of raster data, with only one purpose, to display a detailed image on a map or for the purposes of digitization. Other raster data sets will contain information regarding elevation, a DEM, or reflectance of a particular wavelength of light, LANDSAT.

Raster data type consists of rows and columns of cells, with each cell storing a single value. Raster data can be images (raster images) with each pixel (or cell) containing a color value. Additional values recorded for each cell may be a discrete value, such as land use, a continuous value, such as temperature, or a null value if no data is available. While a raster cell stores a single value, it can be extended by using raster bands to represent RGB (red, green, blue) colors, colormaps (a mapping between a thematic code and RGB value), or an extended attribute table with one row for each unique cell value. The resolution of the raster data set is its cell width in ground units.

Raster data is stored in various formats; from a standard file-based structure of TIF, JPEG, etc. to binary large object (BLOB) data stored directly in a relational database management system (RDBMS) similar to other vector-based feature classes. Database storage, when properly indexed, typically allows for quicker retrieval of the raster data but can require storage of millions of significantly-sized records.

Vector

In a GIS, geographical features are often expressed as vectors, by considering those features as geometrical shapes. Different geographical features are expressed by different types of geometry:

Points

Zero-dimensional points are used for geographical features that can best be expressed by a single point reference; in other words, simple location. For example, the locations of wells, peak elevations, features of interest or trailheads. Points convey the least amount of information of these file types. Points can also be used to represent areas when displayed at a small scale. For example, cities on a map of the world would be represented by points rather than polygons. No measurements are possible with point feature

Lines or polylines

One-dimensional lines or polylines are used for linear features such as rivers, roads, railroads, trails, and topographic lines. Again, as with point features, linear features displayed at a small scale will be represented as linear features rather than as a polygon. Line features can measure distance.

Polygons

Two-dimensional polygons are used for geographical features that cover a particular area of the earth's surface. Such features may include lakes, park boundaries, buildings, city boundaries, or land uses. Polygons convey the most amount of information of the file types. Polygon features can measure perimeter and area.

Each of these geometries is linked to a row in a database that describes their attributes. For example, a database that describes lakes may contain a lake's depth, water quality, pollution level. This information can be used to make a map to describe a particular attribute of the dataset. For example, lakes could be coloured depending on level of pollution. Different geometries can also be compared. For example, the GIS could be used to identify all wells (point geometry) that are within 1-mile (1.6 km) of a lake (polygon geometry) that has a high level of pollution.

Vector features can be made to respect spatial integrity through the application of topology rules such as 'polygons must not overlap'. Vector data can also be used to represent continuously varying phenomena. Contour lines and triangulated irregular networks (TIN) are used to represent elevation or other continuously changing values. TINs record values at point locations, which are connected by lines to form an irregular mesh of triangles. The face of the triangles represent the terrain surface.

Article Source: http://en.wikipedia.org/wiki/GIS

Relating information from different sources

ohmara.rain@gmail.com — Tue, 09 Sep 2008 04:55:00 +0000

From Wikipedia, the free encyclopedia

If you could relate information about the rainfall of your state to aerial photographs of your county, you might be able to tell which wetlands dry up at certain times of the year. A GIS, which can use information from many different sources in many different forms, can help with such analyses. The primary requirement for the source data consists of knowing the locations for the variables. Location may be annotated by x, y, and z coordinates of longitude, latitude, and elevation, or by other geocode systems like ZIP Codes or by highway mile markers. Any variable that can be located spatially can be fed into a GIS. Several computer databases that can be directly entered into a GIS are being produced by government agencies and non-government organizations[citation needed]. Different kinds of data in map form can be entered into a GIS.

A GIS can also convert existing digital information, which may not yet be in map form, into forms it can recognize and use. For example, digital satellite images generated through remote sensing can be analyzed to produce a map-like layer of digital information about vegetative covers. Another fairly developed resource for naming GIS objects is the Getty Thesaurus of Geographic Names (GTGN), which is a structured vocabulary containing around 1,000,000 names and other information about places.

Likewise, census or hydrologic tabular data can be converted to map-like form, serving as layers of thematic information in a GIS.
Article Source: http://en.wikipedia.org/wiki/GIS

Data creation

ohmara.rain@gmail.com — Tue, 09 Sep 2008 04:47:00 +0000

From Wikipedia, the free encyclopedia

Modern GIS technologies use digital information, for which various digitized data creation methods are used. The most common method of data creation is digitization, where a hard copy map or survey plan is transferred into a digital medium through the use of a computer-aided design (CAD) program, and geo-referencing capabilities. With the wide availability of ortho-rectified imagery (both from satellite and aerial sources), heads-up digitizing is becoming the main avenue through which geographic data is extracted. Heads-up digitizing involves the tracing of geographic data directly on top of the aerial imagery instead of through the traditional method of tracing the geographic form on a separate digitizing tablet.

Article Source: http://en.wikipedia.org/wiki/GIS

GPS and Other Emergency Contact Devices

ohmara.rain@gmail.com — Sun, 07 Sep 2008 09:14:00 +0000

By: Victor Epand

What is the best kind of GPS system for you? This depends on what you intend to use it for.
Garmin 12 GPS is very good. There are various models of the 12, 12XL etc. They can be found for under $150. The altimeter is usually off but once you find your position, most of the time the map tells me what my altitude is. They have a pretty decent battery life since you rarely ever use your GPS for 12 hours straight.

The vendors selling GPS units are Garmin and Magellan, those are good brands and can meet your requirements quite well. There is a third player, Brunton (compass makers gone hi-tech). They make very reasonably priced GPS units with lots of bells and whistles. Garmin GPS records the distance travelled, speed, average speed, etc. Make sure you get good battery life and enough memory to be useful.

Mitac Mio 168 comes out well for my requirements but is more expensive, especially if you go for the tom tom mapping software too (voice directions when I'm out on my motorbike!)

Most of the functions on GPS of this sort you can get from a map. Maps on pure GPS are not as good as on a GPS/PDA but good maps for these are usually expensive. Some mountain rescue team members use PDAs with 1:25000 OS mapping data for recording search patterns etc.

You really need to look at your own plans - for instance, most backpackers use GPS to "confirm" their position, and they don't use it to set waypoints, determine compass direction, navigate, etc. Many backpackers use it as an emergency navigation tool in Utah's deep, narrow canyons, where a map and compass can be almost useless.

One word of warning, take very seriously the statement on the front of all GPS units "Do not rely on this unit as the primary source of your navigation." It's always a good idea to have a map and compass with you when engaging in wilderness travel and use them right along with the GPS. It can actually be kind of fun to see how accurate you are with a compass and compare map routes with GPS routes to see why you ended up going the way you did.

What are the numbers on a compass for and how do you use a compass? The numbers on the compass are for degrees or headings. They will tell you what direction to proceed on. The first thing you need to do is figure out what kind of compass you have, a floating dial or a floating needle.

As to emergency contact, you could buy an expensive Iridium/satellite phone - they can get a signal just like a GPS does. They run over $1,000. It may also be possible to rent one. For real emergencies, not simply a vehicle breakdown, there is a GPS signaling device, much like ONStar (GM trademark), that can send an emergency signal. The final thing to do is to check in at the local ranger station, BLM office, forest service visitor center, etc., and see about leaving your itinerary with them, as well as a promise to check-out with them when leaving. If you don't check in, they would send someone out to check on you.

Article Source: http://www.articlesauce.com

GIS for Real Estate Professionals and Buyers-The Ultimate Map Resource

ohmara.rain@gmail.com — Sat, 06 Sep 2008 08:49:00 +0000

By: harrydavis

GIS stands for "Geographic Information Systems." A geographic information system is used for capturing, storing, analyzing and managing data and associated attributes which are referenced to a given point or place. Many local governments have begun to establish these systems for use within their borders and a GIS provides a central access point for geographic information not only for government employees, but also for web users. Austin, Texas has had a sophisticated GIS online for several years.
One advantage for a government entity in setting up a working GIS site is that it provides customers an online way to get various types of information on the web without calling or having to drop by the office, thereby freeing up employees for other tasks. The consumer gets an advantage by being able to view a lot of maps, such as zoning maps, online instead of having to purchase one.
GIS is a great tool for real estate agents, appraisers, buyers and anyone else with a need to look up information about a property, and GIS is becoming more widespread every day. If you live in a medium to large size city, chances are very good that your local city or county planning department has a working GIS right now. Even many small towns have them.
GIS enables the visitor and the real estate professional to view zoning maps, parcel maps, flood maps, aerial photos, and a variety of other information which can be viewed separately or as a grouping of layers on the same map. Most GIS systems provide an address search capability. For some types of properties it may be necessary to zoom in from a map of a larger area. Tools to zoom in and out are always provided.
In an example situation, suppose you search for a home by address and find it on the map. You can then choose from several map layers to add to it from a menu, such as zoning, parcel maps, bodies of water, and more. If you choose to overlay flood zone maps, you will be able to tell if the home lies with a flood plain. This gives the user a way to know if the home is likely to require flood insurance. If you want to know the specific zoning for the home, you can choose to have that map layer added on top. These map "layers" are mostly transparent, meaning that the original map will still be visible.
The local city planning department GIS systems and their corresponding menu systems vary according to the design and the provider, but I have accessed several in my area and found them to be more or less the same in terms of how they operate and they types of information they provide. The beginning GIS user may find these online systems a little confusing at first, but a few experiments should help you to find your way around. These systems continue to evolve to make them easier for nontechnical users to operate. The wealth of useful information they provide makes them well worth the effort to learn.
To locate a GIS for your city, go to your favorite search engine and type in the name of the city and GIS, such as " Austin GIS" in the search box. If you don't find your local GIS this way, go to the city or county web site and look for it there or just contact their office and find out if one exists and where to find it.
Article Source: http://www.articlemap.com

Why GPS Units Are Helpful

ohmara.rain@gmail.com — Sat, 06 Sep 2008 08:23:00 +0000

By: Justin Clark

My family and recently took a trip to Florida. We rented a lovely minivan and spent several days visiting family, animal attractions, etc. When we were planning the trip, we realized that we'd have to either print off a bunch of maps to get everywhere we were going, or rent a GPS unit, or buy a GPS unit to help us get around.

After thinking about the pros and cons of each, we decided it'd be best to buy a GPS rather than doing all that printing of maps or spending the money on simply renting a GPS. We figured we'd end up using it on other trips as well, so the cost would be worth it.

We bought a Garmin 550c off of eBay. What an incredible little piece of equipment! We paid under $200 for it which was a fantastic deal for that brand at the time with a cool array of features.

Our new GPS not only got us where we needed to go, but helped us find new places to visit that were close to where we were. It helped us find beautiful beaches, shoe stores, Walmarts, grocery stores, and all kinds of other places.

My sister came on the trip as well, bringing her husbands new Magellan GPS unit that he got for Christmas. Unfortunately, her Magellan didn't work nearly as well as our Garmin. It often couldn't figure out where she was and got her off course quite a bit.

Obviously, it pays to get the right higher quality brand. It not only saves time, but it also saves gas money because you're not stuck running around town trying to figure out where your GPS left its brains.

So our recommendation is that GPS units are one of the handiest things to take on a trip, you just need to make sure you invest in the right brand! Garmin is one of the better brands, in our experience.

Article Source: http://www.articlemap.com

What is a GIS?

ohmara.rain@gmail.com — Fri, 05 Sep 2008 15:03:00 +0000

From U.S. Geological Survey http://erg.usgs.gov/isb/pubs/gis_poster/

A GIS is a computer system capable of capturing, storing, analyzing, and displaying geographically referenced information; that is, data identified according to location. Practitioners also define a GIS as including the procedures, operating personnel, and spatial data that go into the system.

Article Source: http://erg.usgs.gov/isb/pubs/gis_poster/

Global Positioning System/GPS

ohmara.rain@gmail.com — Fri, 05 Sep 2008 14:42:00 +0000

From Wikipedia, the free encyclopedia
The Global Positioning System (GPS) is the only fully functional Global Navigation Satellite System (GNSS). The GPS uses a constellation of between 24 and 32 Medium Earth Orbit satellites that transmit precise microwave signals, that enable GPS receivers to determine their location, speed, direction, and time. GPS was developed by the United States Department of Defense. Its official name is NAVSTAR-GPS. Although NAVSTAR-GPS is not an acronym[1], a few backronyms have been created for it[2]. The GPS satellite constellation is managed by the United States Air Force 50th Space Wing.
Similar satellite navigation systems include the Russian GLONASS (incomplete as of 2008), the upcoming European Galileo positioning system, the proposed COMPASS navigation system of China, and IRNSS of India.
Following the shooting down of Korean Air Lines Flight 007 in 1983, President Ronald Reagan issued a directive making the system available free for civilian use as a common good.[3] Since then, GPS has become a widely used aid to navigation worldwide, and a useful tool for map-making, land surveying, commerce, scientific uses, and hobbies such as geocaching. GPS also provides a precise time reference used in many applications including scientific study of earthquakes, and synchronization of telecommunications networks.
Article Source: http://en.wikipedia.org/wiki/GPS

From Theodolites to GIS

ohmara.rain@gmail.com — Thu, 04 Sep 2008 09:21:00 +0000

From http://blogs.esri.com/Info/blogs/geographymatters/default.aspx

By GeographyMatters

Originally set up in 1767, the Survey of India is the government's oldest department and in charge of all of the its mapping and surveying efforts. Since coordinating the Great Trigonometric Survey, it has expanded over the years to 23 geospatial data centers and 18 divisions that range in responsibilities from tides to aerial survey. The agency uses GIS extensively in its mapping activities.

The Great Arc (ISBN 0-00-257062-9) by John Keay details the challenges in completing the Survey of India's Great Trigonometric Survey or Great Arc, an epic project that both carefully mapped the country and measured the curvature of the earth.

Begun in 1800 by William Lambton, an English army captain, and completed by his assistant George Everest, for whom the famous Himalayan Mountain was named, the project stretched for nearly 50 years and 1,600 miles.

The survey process was based on triangulation, a method in which a baseline is accurately measured and the angles of the desired triangle are calculated by sighting a point with a theodolite, an instrument used to measure both horizontal and vertical angles. One side of the calculated measurements of the first triangle is then used as the base line for the next triangle and so on. The end result was a triangulation network of varying sizes that progressively moved towards the Himalayas.

This procedure is complicated because the earth is uneven and shaped like an oblate spheroid. This means that the angles of the calculated triangles did not add up to 180 degrees and spherical excess had to be calculated and removed.

Lambton's Great Theodolite used by both William Lambton and George Everest during the Great Trigonometric Survey of India was capable of measuring both the vertical and horizontal access, it weighed approximately half a ton and needed twelve men to carry it. This image was taken from the 'Historical Records of the Survey of India 1830 to 1843', Volume IX plate 6.

Article Source: http://blogs.esri.com/Info/blogs/geographymatters/default.aspx
Posted :Friday, August 15, 2008 9:50 AM by GeographyMatters

Geographic information system

ohmara.rain@gmail.com — Thu, 04 Sep 2008 09:04:00 +0000

From Wikipedia, the free encyclopedia

A geographic information system (GIS), also known as a geographical information system, is an information system for capturing, storing, analyzing, managing and presenting data which are spatially referenced (linked to location).

In the strictest sense, it is any information system capable of integrating, storing, editing, analyzing, sharing, and displaying geographically referenced information. In a more generic sense, GIS applications are tools that allow users to create interactive queries (user created searches), analyze spatial information, edit data, maps, and present the results of all these operations. Geographic information science is the science underlying the geographic concepts, applications and systems, taught in degree and GIS Certificate programs at many universities.

Geographic information system technology can be used for scientific investigations, resource management, asset management, environmental impact assessment, urban planning, cartography, criminology, geographic history, marketing, and logistics to name a few. For example, GIS might allow emergency planners to easily calculate emergency response times in the event of a natural disaster, GIS might be used to find wetlands that need protection from pollution, or GIS can be used by a company to site a new business location to take advantage of a previously under-served market.

Article Source: http://en.wikipedia.org/wiki/Geographic_information_system

Surveying

ohmara.rain@gmail.com — Thu, 04 Sep 2008 03:49:00 +0000

From Wikipedia, the free encyclopedia
Surveyor at work with a leveling instrument.Table of Surveying, 1728 CyclopaediaSurveying is the technique and science of accurately determining the terrestrial or three-dimensional space position of points and the distances and angles between them. These points are usually, but not exclusively, associated with positions on the surface of the Earth, and are often used to establish land maps and boundaries for ownership or governmental purposes. In order to accomplish their objective, surveyors use elements of geometry, engineering, trigonometry, mathematics, physics, and law.

An alternative definition, per the American Congress on Surveying and Mapping (ACSM), is the science and art of making all essential measurements to determine the relative position of points and/or physical and cultural details above, on, or beneath the surface of the Earth, and to depict them in a usable form, or to establish the position of points and/or details.

Furthermore, as alluded to above, a particular type of surveying known as "land surveying" (also per ACSM) is the detailed study or inspection, as by gathering information through observations, measurements in the field, questionnaires, or research of legal instruments, and data analysis in the support of planning, designing, and establishing of property boundaries. It involves the re-establishment of cadastral surveys and land boundaries based on documents of record and historical evidence, as well as certifying surveys (as required by statute or local ordinance) of subdivision plats/maps, registered land surveys, judicial surveys, and space delineation. Land surveying can include associated services such as mapping and related data
accumulation, construction layout surveys, precision measurements of length, angle, elevation, area, and volume, as well as horizontal and vertical control surveys, and the analysis and utilization of land survey data.

Surveying has been an essential element in the development of the human environment since the beginning of recorded history (ca. 5000 years ago) and it is a requirement in the planning and execution of nearly every form of construction. Its most familiar modern uses are in the fields of transport, building and construction, communications, mapping, and the definition of legal boundaries for land ownership.

remark: All words and photos by Wikipedia (http://en.wikipedia.org/wiki/Surveying#Land_surveyor)