thematic mapping blog

Hurtigruten: 5 day TV marathon using Google Earth and Maps

2011-06-18T13:21:00.012+01:00

My workplace, The Norwegian Public Service broadcaster NRK, is currently transmitting a 134 hour boat trip along the coast of Norway, live and non stop! It's already a big hit on Norwegian TV.

Hurtigruten, the Norwegian Express Line, has for well over 100 years been the backbone of coastal Norway, bringing people and goods up and down the weather-beaten coast. Viewers are able to follow every minute of the trip on NRK’s channel 2.

You can see the live position of the ship, MS Nordnorge, on Google Earth (updated every 10 seconds):

[ Fullscreen ]

The live stream is available below and at nrk.no/hurtigruten from Thursday June 16th 2011 until the ship lands in Kirkenes Wednesday June 22nd. Don't expect a lot of action, just relax and follow the great scenery - this is Slow TV!

There's also a Flickr photostream and a twitter hashtag #hurtigruten.

The video material from the forward facing camera and an export from all the ship's data systems will be available for download. Read more about this project on NRKbeta.

Read more:

Cloud mapping by the Guardian

2011-03-25T00:44:00.004Z

One of the great benefits of Google Fusion Tables is the possibility to merge data from multiple tables. The Guardian Datablog is showing an example of how you can combine your data with the Natural Earth tables I presented in my last blog post.

The Guardian is combining their travel advice table with one of my Natural Earth tables to create a merged table. This table is then used to create a choropleth map showing where in the world it's safe to travel (darker colours are countries with stronger warnings):

Fullscreen version

The map is created with the build-in mapping capabilities of Fusion Tables.

Natural Earth vectors in the cloud!

2011-02-02T21:32:00.014Z

Natural Earth is a jewel among public domain datasets. I’ve made the entire vector dataset (175,000 features!) available on Google Fusion Tables (GFT). Now you can easily query and download vector geometries in different formats (KML, GeoJSON, WKT and SVG) with associated attributes. This experiment will show if Google Fusion Tables can be used as a cloud-based feature server.

All 139 Natural Earth fusion tables are listed in this table. Every table is public and exportable. A few features are missing at 1:10 million scale because the polygons where too large for GFT (the character limit for a given cell is 1 million characters). The data features are described on the Natural Earth website. Table names are identical to the original shapefile names.

All tables include 4 geometry columns containing vector data in various formats:

kml_4326: Keyhole Markup Language (KML)
json_4326: GeoJSON geometries
wkt_4326: Well-known text (WKT)
svg_4326: Scalable Vector Graphics (SVG) paths

The geometries are in EPSG:4326 (longitude/latitude, WGS84). I've only included three decimals to save space and bandwidth. The longitude accuracy is approximately 111 m at equator, which should be sufficient for this dataset.

~~Unfortunately, the built-in mapping features of GFT are useless for world maps containing polygons and lines (both line and polygon geometries are displayed as markers at zoom levels less than 5).~~

Update from Google: "I'm delighted to announce an update - Due to some impressive engineering wizardry on our team, the defaults for zoomed-out views are much improved. Tables with less than 1000 features mapped will show lines and polygons for three additional zoom levels. In addition, many of Bjørn's remaining tables have been granted individual exceptions for visualizing within Fusion Tables; any re-use through merging will inherit this exception. Happy mapping!"

You can download the data using the Google Fusion Tables API, and render the vectors in your own web mapping application.

Examples of how to use Natural Earth in the cloud will follow in later blog posts. Stay tuned!

Farewell to Globalis and UNA Norway

2010-09-27T21:12:00.004+01:00

After almost 9 years at the United Nations Association of Norway (UNA Norway), it was time to seek new challenges. On monday I'll start working for the Norwegian Broadcasting Corporation (NRK). I'll miss my great colleagues and UNA-Norway - and my baby, Globalis.

Globalis is now 7 years old. She speaks 5 languages fluently; Norwegian, Swedish, Danish, Finnish and Icelandic. She is very busy teaching thousands of visitors every day about our diverse, unfair and exciting world - by visual means:

Globalis, a lot of clever people have taken part in your upbringing, and I'm sure UNA Norway will give you a long and prosperous life. You're mission in life couldn't be more important!

Please follow Globalis on Facebook!

-----

A vital part of Globalis is the world map collection. So far it contains 40 maps on environment and human impact. The map data was researched, collected and prepared in cooperation with Nordpil and Grid-Arendal.

Mapping with Google Fusion Tables

2010-08-28T16:37:00.005+01:00

My workplace, United Nations Association of Norway (UNA Norway), has 700 member schools across the country. We wanted to include a map on our webpage to show all our members. The map should be automatically updated when new schools are added or removed. From previous experience, I knew that having 700 markers on a single map is problematic. Google Fusion Tables overcomes this limitation in a clever way.

Especially for nerds: We use SugarCRM to keep track of our members. SugarCRM is highly customisable and it's easy to add extra fields for latitude and longitude positions. I wrote a PHP script which synchronises a SugarCRM database (MySQL) with Google Fusion Tables. The script first checks if the last modifed date or the number of rows are equal. If not, the script loops through all rows (members) in the SugarCRM database. If the member exist in Fusion Tables, it's updated if modified date is different. If the member don't exist in Fusion Tables, it's inserted. Fusion Tables members that don't exist in SugarCRM database are deleted. This script helped me to get started.

When the data are available in Google Fusion Tables, it's easy to create an embeddable map:

Full screen view

Google Fusion Tables avoids the browser limitation of showing maximum 200 markers by generating transparent PNG tiles instead of indvidual markers. This url shows you a PNG image of our member schools around Oslo:

The love/hate relationship with GIS (Part 3)

2010-06-04T21:43:00.006+01:00

| Part 1 | Part 2 | Part 3 |

New uses of GIS
There have been a growing number of attempts to combine critical human geography with GIS methods and techniques (O'Sullivan, 2006). Here are some successful examples where researchers informed by social theory have engaged with the technology, rather than to criticise from the outside.

People Participating GIS (PPGIS) emerged out of the critic that GIS further privileged those in power and marginalised others. PPGIS pertains to use GIS to broaden public involvement in policymaking and to promote the goals of non-governmental organisations (NGOs), grassroot groups, and community-based organisations (Sieber, 2006). But it is important to be aware that PPGIS can introduce new set of power relations into a community (Crampton, 2003)

Counter-mapping is a related concept to PPGIS, referring to efforts to contest and undermine power relations and asymmetries in relation to cartographic products (Harris and Hazen, 2006). The term was introduced by Nancy Peluso (1995) describing the commissioning of maps by forest users in Indonesia as a way of contesting state maps of forest areas that had long undermined their interest in those resources.

Jeremy Crampton (2001) says that GIS technology enables us to create exploratory mapping environments in which knowledge can be constructed. This is challenging the prevailing picture of cartography as the communication of information form the cartographer to the map reader. Since maps are part of a general discourse of power, mapping should proceed through multiple, competing visualisation which are made on the spot by the user. Exploratory mapping environments are noe now easier to create with recent advances in web technologies and standards. This enables us to embed information from various sources and in various forms (maps, images, video, sound and text). The user can to a large extent determine what information is to be displayed and in what context. It is important to mention the digital divide, as exploratory mapping is only effective when people have access to the technology and knowledge to use it (Crampton and Krygier, 2005).

Combining the best of both worlds
The love/hate dichotomy with GIS seems to be related to the opposition between quantitative and qualitative research. Pavlovskaya (2006) sees this as en extension of different epistemologies and not because these methods are incompatible. For the supportes and critics alike, GIS had been firmly rooted in the quantitative camp. Pavlovskaya finds this misleading, as GIS is neither stictly quantitative nor qualitative but may be used in different types of research. Geographic databases have the capability of storing more than numerical information, and there are examples where qualitative researchers have worked with unconvential GIS data sources. As mentioned above, narratives, hand-drawn maps, graphics, photos and videos can also be stored in these databases. Feminist geographers have begun to model individual experience as emotions or webs of daily economic practices (Pavlovskaya, 2006).

Geographers have also revisited the usefulness of quantitative methods as they no longer cling to the idea that quantitative methods allow objective research, recognising that knowledge is situated (Marshall, 2006). I tend to agree with Openshaw that "the modern geographer should be a pragmatist and seek to use any and all available methods, mixing and matching different tools and philosophies, as when and were appropriate" (Openshaw, 1992). Dobson (2002) belives that "a century from now, science historians will look back and decide GIS was a major revolutionary force in science and society, not because we made better maps, but because we forced disciplines to talk to one another." Future will tell if GIS becomes the glue between quantitative and qualitative research.

| Part 1 | Part 2 | Part 3 |

References

Crampton, J., 2001, "Maps as social constructions: power, communication and visualization", Progress in Human Geography, 25(2), pp. 235-253
Crampton, J., 2003, "How can Critical GIS be defined?", GeoWorld, 16. p. 54
Crampton, J., Krygier, J., 2006 "An Introduction to Critical Cartography", ACME: An International E-Journal for Critical Geographies, 4(1), pp. 22-23
Dobson, J., 2002, "What's new about GIS?" GeoWorld, 15(3), pp. 22-23
Harris, L., Hazen, H., 2006, "Power of Maps: (Counter) Mapping for Conservation", ACME: An International E-Journal for Critical Geographies, 4(1), pp. 99-130
Marshall, A. 2006, "A critique of the development of quantitative methodologies in human geography", Radical Statistics, 92.
O'Sullivan, D., 2006, "Geographical information science: critical GIS", Progress in Human Geography, 30(6), pp. 783-791.
Openshaw, S., 1992, "Further thoughts on geography and GIS: a reply", Environment and Planning A, 24, pp. 463-466
Pavlovskaya, M., 2006 "Theorizing with GIS: a tool for critical geographies?", Environment and Planning A, 33, pp. 2003-2020
Peluso, 1995, N., 1995 "Whose woods are these? Counter-mapping forest territories in Kalimantan, Indonesia", Antopode, 27(4), pp- 383-406
Sieber, R., 2006, "Public Participation Geographic Information Systems: A Literature Review and Framework", Annals of the Association of American Geographers, 93(3), pp. 491-507

The love/hate relationship with GIS (Part 2)

2010-06-04T14:33:00.020+01:00

| Part 1 | Part 2 | Part 3 |

Military connections
"The war against Iraq in 1990-91 was the first full-scale GIS war". This is the opening line in a paper by Neil Smith (1992) in the Progress in Human Geography journal. Smith describes the military roots of GIS and how the techology is (mis)used in modern warfare. Technology does not cause war, but Smith argues that techniques are not easily separatable from their uses. GIS are making war more "doable". These connections were clearly visible in the air and land operations, Operation Desert Storm, of the first Gulf War. Digitised map data was provided by military and scientific agencies. 3D simulations were used to navigate through the desert, and "Geo-smart" bombs were equipped with a video camera so their way to the target could be screened by CNN. Smith calls this a "perverse extravaganza" as the war claimed an estimated 200 000 Iraqi lives. Smith is conserned how GIS, combined with modern weapon systems, enables us to forget the actual effects of war by substituting a slick virtual reality (Crampton, 2004). The military connections of GIS have become stronger since Smith's paper was published (Goodhild, 2006), but the virtual reality version is "harder to sell" when Al Jazeera is showing the real effects on the ground.

Crampton (2004) makes a point that we now live through the second GIS war, but it is occuring in a very different way: through "war on terrorism" and "security". He is concerned about the freedoms we are in danger of giving up in the name of security, and how the GIS industry is becoming a "research arm of the security industry". This leads us to another big critique of GIS; its potential use for electronic surveillance.

Privacy, surveillance and geoslavery
The introduction of GIS has raised consern about information privacy, primarly due to its capacity of integrating spatial information and personal information from different sources (Dobson and Fisher, 2003). The technical practise of geodemographics has been especially criticised (Goss, 1995; O'Sullivan, 2006). Geodemographics is an information technology that enables marketers to predict behavioural response of consumers based on statistical models of identity and residential location (Goss, 1995). Its main use is to find new markets for products and services by precisely locating potential customers. A geodemographic system combines GIS with electronic databases composed of records of consumer indentity and behaviour. Goss (1995) criticies this practise as it's based upon a rationality that desires to bring the processes of consumption under the control of the production regime. He is also concerned about how geodeomographics displays a strategic intent to control social life, and how the segmentation schemes imply social judgement.

Dobson and Fisher (2003) have gone even further by introducing the term geoslavery for a potential threat in the near future. Geoslavery is defined as "the practise in which one entity, the master, coercively or surreptitiously monitors and exerts control of another individual or slave (Dobson and Fisher, 2003:47). Today, these human tracking systems are combining GPS receivers, mobile phones, radio transmitters and GIS technology to support Location Based Services (LBS). It is stated, in a quite paranoic way, that the "countles benefits of LBS are countered by social hazards unparalleled in human history". I presume theay want to provoke since their pricipal objectives in to forewarn the public, foster debate and propose remedies where there is lack of legislation.

| Part 1 | Part 2 | Part 3 |

References

Crampton, J. 2004, "Rethinking GIS and [homeland] security", GeoWorld, 19(3), p. 22.
Dobson, J., Fisher, P., 2003, "Geoslavery", IEEE Technology and Society Magazine, spring 2003, pp. 47-52.
Goodchild, M., 2006, "GIScience Ten Years After Ground Truth", Transactions in GIS, 10(5), pp. 687-692.
Goss, J., 1995, "We Know Wo You Are and We Know Where You Live: The Instrumental Rationality of Geodemographic Systems", Economic Geography, 71(2), pp. 171-198.
O'Sullivan, D., 2006, "Geographical information science: critical GIS", Progress in Human Geography, 30(6), pp. 783-791.
Smith, N., 1992, "History and philosophy of geography: real wars, theory wars", Progress in Human Geography, 16(2), pp- 257-2718.

The love/hate relationship with GIS (Part 1)

2010-06-03T16:54:00.020+01:00

| Part 1 | Part 2 | Part 3 |

Geographical Information Systems (GIS) did not ease into the geography departments without friction, and it is has been said that "academic geographers often have a love/hate relationship with GIS" (Schuurman, 2004:2). In this blog series, I try to reveal this dichotomy by looking at the historical background and the arguments put forward. As the love/hate relationship weakened in the second half of the 90s, we see how co-operation between GIS scholars and their critics fostered a new GIS discourse. The series ends by looking at further possibilities of combining quantitative and qualitative methods with GIS.

Geographical information systems (GIS) influence many aspects of the modern society. We leave locational, electronical tracks whenever we use a credit card, turn on our mobile phone or send an email. Car navigation systems are becoming state-of-the-art in new automobiles. Web mapping tools like Google Earth are bringing the ideas of GIS to a wide audience. Many countries and organisations are working on their spatial data infrastructures. GIS was not something that developed within the geography departments, and the advancement of tools and techniques are to a large extent done by actors outside academia.

Science wars in geography

"It's funny how old (and tiresome?) debates in geography never die, they just find new battlefields" (Walton 1995:6)

The love/hate relationship with GIS can be traced back to the criticism of the quantitative revolution. The quantitative revolution was a major turning point in geography in the 1950s and 60s (Marshall, 2006). It marked a change in the methods of geographical research, from descriptive (ideographic) geography to an emperical law making (nomothetic) geography. The quantitative revolution was based on basic ideals of logical positivism; that only one scientific method exists, that knowledge is neutral and value free, and that all science should be based on standards of accuracy and precision in the physical sciences.

There was a growing criticism against use of quantitative methodologies in the 1960s and 70s (Marshall, 2006). This was due to the positivist underpinnings of the approach. It was claimed that value free research was not possible in social research, and that quantification gave a false sense of objectivity. Quantitative researchers were also criticised for treating people as objects without consideration of the values and meaning that makes individuals human. It was argued that a purely quantitative approach looked at how things seemed to be, and not considering the human capacity to change the configuration of societies. As a result of this criticism, quantitative methodologies experienced a downturn in popularity in the 80s.

The GIS criticism in the 90s
The criticism of GIS in the early 1990s echoes the criticism of the quantitative revolution. A debate that had bubbled under the surface since the mid-1980s (Smith, 1992) was triggered by an editorial comment of Peter J. Taylor (1990) in Poltical Geography Quaterly. Here, Taylor writes about the "positivist geography's great revenge". He states that "quantifiers" have embraced GIS by retreating from knowledge to information, and "left geography intellectually sterile" as a "high-tech trivial pursuit".

The climate was not getting better by the strong academic advocacy of GIS (Smith, 1992). Openshaw (1991:628) was maybe the biggest provocateur by describing GIS as "an emerging all-embracing implicit framework capable of integrating and linking all levels of past, present, and possible future geographies". He was further fuelling the debate by calling GIS critics "poor fools" and "technical cripples". Another GIS critic, Neil Smith, was responding by saying: "the problem lies in outlandish diciplinary ambitions, the radical exclusion of other perspectives, and the dangerous and self-defeating renunciation of an intellectual (as opposed to technical) agenda that too often accompany the programmatic advocacy for GIS" (Smith, 1992).

The different arguments were assembled in a book called Ground Truth, edited by Pickles (1995). The book challenged geographers to examine the role of GIS in mediating power relations and political practises, producing spatial knowledge, and altering physical and social environments (Elwood, 2006). GIS was criticised in the ways it further privileged those in power, who had access to the technology, and marginalised others (Goodchild, 2006).

Many geographers thought that the advent of GIS created a biased perception of the academic discipline, as it only represented one lens to the physical and social world (Schuurman, 2004). Research projects not involving GIS, suffered from research grants and lack of attention. In the early 1990s, doctoral students looking for academic positions found that most of them required expertise in GIS. The new technology was seen as a direct threat to the positions of professional cartographers (Pickles, 2006). It is obvious that the large investments in GIS were streching the civility of sub-fields within geography departments.

Technical advances in GIS preceded the ability to understand its potential effects (Schuurman, 2004). As mentioned above, GIS did no derive its power solely from the field of geography, most came from outside (Openshaw, 1991). When GIS was introduced in geography it did not have a fixed and secure identity. There was, and still is, a myriad of ways GIS could be defied and perceived. For an academic researcher, GIS is not only a piece of software, but a scientific approach to a problem.

| Part 1 | Part 2 | Part 3 |

References

Goodchild, M., 2006, "GIScience Ten YEars After Ground Truth", Transactions in GIS, 10(5), pp. 687-692.
Marshall, A. 2006, "A critique of the development of quantitative methodologies in human geography", Radical Statistics, 92.
Openshaw, S., 1991 "A view on the GIS Crisis in Geography, or, using GIS to put Humpty Dumpty back together again", Environment and Planning A, 23, pp. 621-628.
Pickles, J. (ed), 1995, Ground Truth: The Social Implications of Geographical Information System, New York, guilford.
Schuurman, N., 2004, "Introducing the Identities of GIS" in GIS - a short introduction, pp. 1-3, Blackwell Publishing.
Smith, N., 1992, "History and philosophy of geography: real wars, theory wars", Progress in Human Geography, 16(2), pp- 257-2718.
Taylor. P.J., 1990, "GKS", Political Geography Quarterly, 3, pp. 211-212
Walton, J., 1995, "How real(ist) can you get?", Professional Geographer, 47, pp 61-65

Thematic Mapping in Slovakia

2010-05-10T12:51:00.002+01:00

Inspired by this website (thematicmapping.org), Vladimír Bačík created a great-looking site showing statistical data for Slovakia using Google Earth and KML.

Selected variables can be displayed on the territory of districts and regions, as well as the whole Slovak Republic. Various thematic mapping techniques are in use.

Give it a try!

Natural Earth Browser

2010-01-03T20:30:00.007Z

My holiday project, apart from skiing, was to play with the new Natural Earth dataset. This is a public domain map dataset available at three scales, 1:110m, 1:50m and 1:10m. By combing raster and vector data you can make a variety of visually pleasing maps. You can use my Natural Earth Browser to study the great linework of Natural Earth.

Natural Earth Browser consists of 13 map layers, 3 base maps and 10 overlays, which are shown in the original projection (Geographic, WGS84 datum). The map overlays are rendered as transparent map tiles. The layers can be reordered by drag-and-drop, and you can change the opacity of each layer with the slider control. Small scale data (1:110m) are shown for zoom level 1 and 2, medium scale data (1:50m) for zoom level 3 to 5, and large scale data (1:10m) for zoom level 6.

Natural Earth Browser was created with a variety of open source tools. Map tiles from raster data was created with MapTiler and optimised with pngng. Map tiles from vector data was styled with Mapnik and pre-genereated with TileCache. The map interface is based on OpenLayers, Ext JS and GeoExt.

The Natural Earth dataset is more than a collection of pretty lines. The vector data (shapefiles) are accompanied with attribute tables which can be used for styling and labeling purposes. I've just started digging into the styling capabilities of Mapnik, and I'm not realising the full potential of this toolkit. I had to spend some time skiing when natural earth looked like this:

I wish my readers a joyful and exciting new year!

Introducing Atlas of Norway (norgesatlas.info)

2009-12-03T18:00:00.002Z

Great news! On December 1st, the Norwegian Mapping Authority (NMA) launched a series of map services. The best and most detailed maps of Norway are now freely available. You can browse the maps in my new web application: norgesatlas.info (Atlas of Norway). The following map layers are fetched from NMA:

Sjøkart = Nautical chart
Topografisk = Topographic map (very nice!)
Fylker og kommuner = Administrative boundaries
Sjødybder = Sea depths
Sjøgrenser = Maritime boundaries

Below are a few examples depicting Foldøy island - 1 square km of beauty in southwest Norway.

Google Satellite, highest resolution available.

Google Streets, highest level of detail available.

Nautical chart from NMA.

Topographic map from NMA.

Topographic map and sea depths from NMA.

Large scale topographic map from NMA.

Grazing land on Foldøy.

NMA maps can be accessed as a Web Map Service (WMS) or as cached map tiles for fast retrieval. Both Google Maps and Bing Maps tiling schemes are supported, as well as WMS-C. Limits are 300 requests per end-user per day for the WMS and 10000 request per day for the cached version (Terms of Use).

According to this blog post, the NMA map services are based on open source software: MapServer, PostGIS and GeoWebCache. Norgesatlas.info is based on OpenLayers, ExtJS and GeoExt, - great tools to build web mapping applications.

http://norgesatlas.info

Related post: Thematic Mapping in Norway

Using KML for Thematic Mapping - Research Paper Now Available

2009-10-20T10:00:00.012+01:00

My research paper, Using KML for Thematic Mapping, is now available for download (PDF, 2.3 MB). This is the first part of my MSc GIS thesis from University of Edinburgh. The second part of my thesis, describing the Thematic Mapping Engine, is already available on this page. The thesis was awarded with distinction and an invitation to Googleplex.

This is a short summary:

Why use KML for thematic mapping?

The purpose of this paper is to examine how KML, Keyhole Markup Language, can be used for thematic mapping. A thematic map displays the spatial pattern of a social or physical phenomenon, such as population density, life expectancy or climate change. Thematic mapping has a long history in cartography, but the new geobrowsers tend to have a stronger focus on detailed satellite imagery and general-reference maps than on more abstract data sources.

"From the perspective of the social sciences, the focus on content that is visible from above is problematic, given the abundance of more abstract data sources. A new generation of techniques is needed that can mash such data with the Google Earth base, creating more powerful ways of communicating what social scientists know about the surface of the Earth."

- Michael F. Goodchild, Geographic Visualization: Concepts, Tools and Applications, 2008

Due to their huge public interest and relative accessibility, geobrowsers are potentially capable of bringing thematic maps or visualizations to a wider audience. By allowing the user to visualise statistical data in an external geobrowser instead of a built-in mapping application, data from various sources can be more readily combined. The value of the statistical data can be increased if the user is allowed to tie it to other data sources. This can be both quantitative and qualitative data, like text, pictures and videos. Furthermore, geobrowsers can also be embedded in other web applications to enhance their utility and general ability to contextualise information.

Why not?

Using geobrowsers for thematic mapping can, however, be problematic. For 2-D geobrowsers, the big players in the web mapping world (Google Maps and Microsoft Live Search Maps) use the Mercator projection. Mercator is a good choice for zoomable satellite imagery, but less suitable for thematic world maps due to the great area distortions. Current 2-D viewers also have problems rendering large vector-based maps, due to web browser limitations.

3-D virtual globes, like Google Earth and Microsoft Virtual Earth, partly avoid the distortions of map projections. Since images still have to be projected onto a flat screen, virtual globes use the Perspective Orthographic projection, which is also the projection inherent in the human visual system (Goodchild, 2008). Unfortunately, the ability to see the whole Earth at once is lost when thematic maps are rendered on a globe. It is also difficult to estimate the area or the volume of proportional symbols when seen in perspective.

How?

Current possibilities for making proportional symbol maps, chart maps, choropleth maps, prism maps and animated maps with KML are presented in the paper. These techniques are described in detail in the supporting document (PDF, 7.4 MB). The paper also compares KML with other stadards of interest; Geography Markup Language (GML), Styled Layer Descriptor (SLD), Symbol Encoding (SE) and Scalable Vector Graphics (SVG).

Conclusion

It is possible, with some inventiveness, to use KML for thematic mapping. There are, at least, three different ways of making proportional symbol maps: by scaling image icons, by calculating the longitude/latitude vertices of regular polygons, or by scaling 3-D Collada objects. Furthermore, an external web service, like Google’s Chart API, can be utilised to create chart maps. Choropleth maps can be generated by using shaded polygons, and turned into prism maps by adding an altitude value to each coordinate tuple. The KML time primitives can be used to create temporal or animated maps. There is also an option to distribute thematic maps as (raster) map tiles, instead of via a vector format.

However, the current KML standard is not optimised for thematic mapping, as it was not explicitly designed for this purpose. Many of the techniques presented in this paper can be characterised as “hacks”, because KML elements are used in ways for which they were probably never originally intended. There are consequently issues that need to be resolved in future KML versions, like the “polygons-hole problem” that occurs when prism maps are rendered on a 3-D globe. There is also a lot of redundancy in the data, as height (altitude) values have to be repeated for each vertex in a polygon, and entire feature structures need to be repeated for every time step in an animation. Proportional symbols would be easier to create if KML supported regular polygons natively. Collada objects would be more suitable for thematic mapping if they were made clickable.

KML needs to be harmonised with other OGC standards to achieve greater interoperability and more extensive use. Particularly important for thematic mapping are styling rules for transforming feature and attribute data into various 2-D and 3-D representations. Such styling rules are already present in the OGC Symbology Encoding specification. KML also needs enhanced graphics functionality and symbolisation constructs. Instead of reinventing the wheel, this functionality could be modelled after the Scalable Vector Graphics (SVG) specification. The KML standard, combined with powerful and accessible geobrowsers, like Google Earth, has a great potential for thematic mapping. Hopefully, this potential will also be realised by the OGC and geobrowser vendors, and lead to future improvements and native support for thematic mapping functionality in the open standards promulgated by OGC and the vendors.

Acknowledgments

I would like to acknowledge and extend my gratitude to the following people who have made the completion of this dissertation possible:

Bruce Gittings and James Reid, for their supervision, advice and constructive criticism.

To those whom I haven’t met, but who have given me valuable feedback and advice on my thematic mapping blog.

And to all the people who believe in open data, open access and open source solutions. This dissertation will be my contribution.

You're welcome to post your feedback in the comments!

Projecting KML with OpenLayers and Proj4js

2009-10-08T20:05:00.012+01:00

Back in May I was waiting for a geobrowser capable of showing KML in different projections. Inspired by a great blog series by Richard Marsden (1, 2, 3, 4, 5, 6 & 7!), I've done some experiments with OpenLayers and Proj4js.

Proj4js is a JavaScript library that provides methods for coordinates transformation between map projections and longitude/latitude. OpenLayers integrates with Proj4js, and by combining these libraries your able to project KML in pure JavaScript. No server side dependencies!

This example shows a KML document from the Thematic Mapping Engine in three different projections (Mollweide, Sinusoidal and Equal Area Cylindrical). The KML document contains borders, but these are not extracted and displayed by OpenLayers.

OpenLayers and Proj4js rocks! :-)

Generating KML from CMS - and how to make mashups without a key

2009-09-29T10:58:00.016+01:00

After a great thematic mapping timeout this summer, it feels good to start blogging again. In my first autumn post, I want to write about the benefits of using a Content Management System (CMS) to create KML documents. I will also show how you can create Google Maps and Google Earth mashups without a map key.

My office is currently running a UN relay race across Norway. 19 schools are participating, one school from each county. It's possible to follow the race on our webpage - on a 2-D map and as a 3-D tour. I wanted make a dynamic solution which could be reused and automatically updated as the race went on.

I ended up playing with our content mangement system. A well designed CMS should enable you to output content in various formats, not only HTML. We're using eZ Publish, maybe the best open source CMS in the world. eZ Publish enables you to create your own content classes and objects. Combined with the built-in template system, I was able to output my new content objects as KML instead of HTML.

One KML is generated for the lightweight 2-D map. You can embed this map on any webpage using an iframe containing a link to google maps and the KML. No Google Maps API key is needed, and the map is updated whenever the KML is updated by the CMS.

Show larger map

The other KML makes use of the new touring capabilities of Google Earth 5. By using KML scripting instead of JavaScript you can easily embed your tour on any webpage. This tour will show you all the schools participating in the relay race.

Every school are asked to make a letter which will eventually become a sentence.

My last tip-of-the-day:
When creating KML on the fly, you can benefit from some hidden features of the Google Chart API. The numbered map pins above are created with this API (it's a problem that Google Maps always renders KML icons as 32 x 32 pixels). KML only support images as screen overlays, but I was able to add dynamic text by using this feature of the Google Chart API (see top left corner of the tour).

Thematic Mapping Timeout

2009-05-29T22:00:00.004+01:00

The summer and everlasting days are here. I need to prioritize my free time in the upcoming months. All the work reflected on this site has been unpaid - and it won't be continued unless I'm able to earn a salary...

I wish my readers a great summer (or winter if you're down under)!

KML projections

2009-05-27T13:01:00.018+01:00

I'm waiting for a geobrowser capable of showing KML maps in different projections. The projections commonly used by geobrowsers are not the best choice for thematic world maps. Many cartographers dislike thematic maps rendered on virtual globes, and the Mercator projection is not suited for large area maps. Greenland looks like the same size of South America, while it is actually 8 times smaller.

The coordinate system of KML is geographic (latitude/longitude) coordinates on the World Geodetic System of 1984 (WGS84) datum. Geobrowsers use different projection techniques to render a KML document. Google Earth uses a General Perspective projection, which is similar to the Orthographic projection (see Larry Moores informed speculation of the Google Earth projection). Google Maps and Microsoft's Live Maps both use Mercator projection, which is a good choice for a map that can be panned and zoomed seamlessly.

My favorite projection for world maps is Winkel Triple, which is the standard projection for maps made by National Geographic. How can I display my KML based thematic maps in a Winkel Triple projection?

Axis maps recently announced indieprojector. This is a web service (based on Adobe Flash) that allows you to (re)project KML files and export the result as SVG. I tried the service with one of my choropleth maps from the Thematic Mapping Engine.

The above image shows my KML file in Google Maps using the Mercator projection.

Indieprojector nicely and quickly projects my KML file, but the service is not preserving colour styles. When will we see a Flash based KML viewer capable of showing KML documents (with styles!) in various projections?

And what about raster data - is Flash capable of converting image tiles into a seemless Winkel Triple projection?

Introducing Thematic Mapping API

2009-05-20T15:19:00.002+01:00

The brand new Thematic Mapping API enables you to create KML based thematic maps from your own data source. This JavaScript library is the missing link between Google Visualization API and Google Earth API (or other geobrowser APIs supporting the KML standard).

A few examples:

The API is still in beta. Please email me if you would like to try the new API: bjorn[at]thematicmapping.org

Thematic Mapping API will be free to use on non-commercial sites.

Virtual Globes are a good idea for thematic mapping

2009-04-17T20:16:00.010+01:00

It's important to seriously discuss and measure the quality of different thematic mapping techniques. I appreciate the critique from Dr. Mark Harrower on the Axis Maps Blog. I encourage everyone to read Mark's blog post - it's an interesting and timely read. This is a quick response to this critique - more blog posts will follow.

In short, I agree with most of the arguments put forward, but I disagree with the conclusions:

I agree that my 3-D graduated symbol maps are "pure chart junk", but there are some good examples of 3-D symbol maps. (See previous blog post)
I disagree that 3-D prism maps are chart junk - but thematic world maps on a 3-D globe are problematic. (See previous blog posts: [1], [2], [3]).
I very much disagree that Virtual Globes are a bad idea for thematic mapping, but it's certainly not the only or the ultimate way of showing thematic maps.

I hope more people will engage in this important debate. What is your opinion about 3-D visualisations?

Update 28 April: This issue is currently debated on Axis Maps Blog, Google Earth Design and PTS Blog.

KML in Research Award to thematicmapping.org

2009-03-09T18:41:00.009Z

Today, Google announced that one of my KML visualisations won a prize in the KML in Research contest. The animated prism map shows Global Infant Mortality from 1960 to 2005. The statistical data was downloaded from UNdata, a great resource for global statistics.

The statistics can be explored in time and space. Click here to download the KMZ file.

My dissertation, Using KML for Thematic Mapping, was also awarded the MSc Dissertation Prize at University of Edinburgh. The second part of my dissertation gives a detailed description of the Thematic Mapping Engine, and can be downloaded from thematicmapping.org.

My Google Tech Talk

2009-02-20T13:37:00.005Z

My Google Tech Talk "Using KML for Thematic Mapping" is now on YouTube:

Poor video quality, but the slides are also available on Slideshare:

You can try the Thematic Mapping Engine online, and download the source code and documentation. Some funding is required to make a general purpose library for KML based thematic maps. Any ideas?

Merry Christmas and Happy New Year!

2008-12-19T05:56:00.014Z

I need a vacation from blogging and computers, so I'm going to take one. Have a great Christmas and a Happy New Year! I'll be back in 2009.

(The population prism map is from Edmar Moretti's Brazilian version of the Thematic Mapping Engine. The highest prism is São Paulo, with its metropolitan area ranking seventh among the largest urban areas in the world.)

Michael Jones, Google Earth Chief Technologist, in live webcast at AGU Fall meeting today

2008-12-15T10:40:00.004Z

The lecture is titled The Spread of Scientific Knowledge from the Royal Society to Google Earth and Beyond and will be given at 6:30 pm San Francisco time.

Watch AGU webcast

Thematic mapping at Googleplex

2008-12-13T18:11:00.000Z

After I handed in my MSc thesis in August, Google invited me to San Francisco to present my work. Yesterday, I gave a tech talk at Googleplex about the Thematic Mapping Engine (now open-source) and how KML and Google Earth could be improved to better support popular thematic mapping techniques. My slides are available on SlideShare.

My talk was filmed and will probably appear online. I was a bit nervous during the presentation, so its not my best performance :-&

Anyway, I really enjoyed the discussions with the geo developers, the lunch talks, and the guided tour around Googleplex. Thanks Google!

The next event is the AGU 2008 Fall Meeting starting on Monday. I'm an invited speaker at the Virtual Globes at AGU session on Thursday.

Thematic Mapping Engine: Source code and technical documentation now available

2008-12-08T20:41:00.015Z

Many people have asked, - and today, I've released the source code of the Thematic Mapping Engine (TME) under a GPLv3 license. The engine takes statistical data, spatial features and thematic mapping parameters as input and returns a KMZ file. This file can be viewed in Google Earth, or other geobrowsers supporting the KML standard. TME can be accessed from a web interface or a PHP script.

TME web interface
With the TME web interface, thematic maps can be created in a web browser, without a single line of code. This is achieved through an interactive web form where the user can select between statistical indicators and various thematic mapping techniques. Mapping parameters, like the colour and size, can be readily changed. The form returns a KMZ file which can be visualised directly in the web browser using the new Google Earth plug-in, or downloaded to a computer.

TME Application Programming Interface (API)
The Thematic Mapping Engine can also be used as an application programming interface (API). This allows thematic maps to be created with a few lines of PHP code. Existing or new applications can use this API to add thematic mapping functionality. This is the code required to create a choropleth map:

include ('TME_MySQL_DataConnector.php');
include ('TME_Engine.php');

$dataConnector = new DataConnector();
$dataStore = $dataConnector->getDataStore(68, 2005, 0);

$parameters = array(
'mapType' => 'choropleth',
'indicator' => 68,
'year' => 2005,
'classification' => 'equal');

$map = new ThematicMap($dataStore, $parameters);
$file = $map->getKML();

Requirements
The Thematic Mapping Engine requires the following software (all are open source and available free of charge):

PHP 5
MySQL 5+
Apache HTTP Server
Ext JS 2.1
Google Earth Plug-in

Documentation
This PDF document (7 Mb) gives a detailed description of the Thematic Mapping Engine. The documentation is available under a Creatice Commons Attribution-Share Alike License 3.0.

You should have a basic knowledge of PHP, MySQL and JavaScript before installing the Thematic Mapping Engine.

Download the TME source code on Google Code.

Enjoy!

Thematic mapping techniques - a summary

2008-12-07T14:08:00.007Z

Thematic maps have become a primary mechanism for summarising and communicating the increased volumes of geographically related information. This blog post is a short summary of the most common thematic mapping techniques.

Jaques Bertin (1967) established a graphic system of visual variables, which represents an universally recognized theory of the cartographic transcription of geographical information (Koch, 2001). Visual variables describe the perceived differences in map symbols that are used to represent geographical phenomena (Slocum et al., 2005). Bertin’s system has been subsequently modified by various cartographers, and the visual variables presented below are based on Slocum et al. (2007), which add 3-D symbolisation.

(Image from InfoVis:Wiki)

Cartographers commonly distinguish between point, line, area and volume symbolisation (Robinson et al., 1995; Slocum et al., 2005). These distinctions may be summarised as follows:

A point symbol refer to a particular location in space, and is used when the geographical phenomena being mapped is located at a place or is aggregated to a given location (MacEachren, 1979). Differentiation among point symbols is achieved by using visual variables, like size, colour and shape. Common thematic mapping techniques using point symbols are dot maps and proportional symbol maps. On a dot map one dot represents a unit of some phenomena, and dots are placed at locations where the phenomenon is likely to occur (Slocum et al., 2005). A proportional symbol map is constructed by scaling symbols in proportion to the magnitude of data occurring at point locations. These locations can be true points or conceptual points, such as the centre of a country for which the data have been collected.

Line symbols are used to indicate connectivity or flow, equal values along a line and boundaries between unlike areas (MacEachren, 1979). Line symbols are differentiated on the basis of their form (e.g. solid line versus dotted line), colour and width. Common thematic mapping techniques using line symbols are flow maps and isarithmic maps. Flow maps utilise lines of differing width to depict the movement of phenomena between geographical locations (Slocum et al., 2005). Isarithmic maps depict smooth continuous phenomena, like rainfall or barometric pressure (Slocum etal., 2005).

Area symbols are used to assign a characteristic or value to a whole area on a map. Visual variables used for area symbols are colour, texture and perspective height (Slocum et al., 2005). The choropleth map is probably the most commonly employed method of thematic mapping, and is used to portray data collected for enumeration units, such as countries or statistical reporting units. While choropleth maps reflect the structure of data collection units, dasymetric maps assume areas of relative homogeneity, separated by zones of abrupt change. The country statistics used in the Thematic Mapping Engine can be considered as areal phenomena, because the statistical values are associated with political units specified as enclosed regions.

Volume symbols can be considered as 2½-D or true 3-D (Slocum et al. 2005). The first can be thought of as a surface, in which a geographical location is defined by x and y coordinate pairs and the value of the phenomenon is the height above a zero point. An example is prism maps which uses perspective height as the visual variable. 3-D symbols can be used to represent true 3-D phenomena, like the concentration of carbon dioxide (CO2) in the atmosphere or geological material underneath the earth’s surface (Slocum et al., 2005).

I'm interested in how these techniques can be represented in KML. You'll find several examples on this site. Please provide other examples by adding a comment. Especially, I would like to see examples of dot maps, flow maps, isarithmic maps and dasymetric maps in KML.

References:

Bertin, J., 1967, "Semiologie Graphique", Paris
Koch, W. G., 2001, "Jaques Bertin’s theory of graphics and its development and influence onmultimedia cartography", Information Design Journal 10(1), pp 37-43, John BenjaminPublishing Company
MacEachren, A. M., 1979, "The Evolution of Thematic Cartography / A Research Methodology and Historical Review", The Canadion Cartographer Vol 16, No 1 June 1979, pp 17-33
Robinson, A. H., Morrison, J.L., Muehrcke, P.C., Kimerling, A. J., Guptill, S. C., 1995, "Elements of Cartography", Sixth Edition, John Wiley & Sons
Slocum, T. A., McMaster, R. B., Kessler, F. C., Howard, H. H., 2005, "Thematic Cartography and Geographic Visualization", Second Edition, Person Education Inc.