Wednesday, March 9, 2011

Fusion Tables for Volunteered Geographic Information (VGI)

VGI Background: There is a lot of discussion about Maps Crowdsourcing (or Volunteered Geographic Information - VGI) on the web at the moment. The excellent Geospatial Revolution clips are an example, this one discusses VGI as used by Open Street Map and Ushahidi in Haiti:



Note: Starts playing at relevant point in movie clip

I've just revamped a lecture for next week discussing VGI in depth and I wanted to get students to create and upload some VGI data but also to understand how to create a very simple VGI system. The solution was Google Fusion Tables.

Fusion Tables Background: For a while now I've heard Mano Marks amongst others pushing the geo capabilities of fusion tables (up coming where 2.0 example), this is the first time I've found an application for them. Neo-Geography is a term for all the new uses of interactive maps and map like visualisations appearing on the web, services like Google Maps, Google Earth are examples, they principally allow the public to visualise geographic data. What is so different about fusion tables is that they offer the ability not just to visualise but also to get into simple analysis of geographic data. Thus in Google Earth I can see Haitian refugee camps but with Fusion tables, it becomes easy to color code them by size. Fusion tables are also free and a lot more simple to operate than desktop GIS.

HowTo: Create VGI Thematic map: The following HowTo takes you through the steps of creating a database, uploading VGI data in the forms of polygons, defining a palette and outputting the result.

1] In GEarth digitise a number of polygons and give each of them a variable value (just 2 digits, no text) in the description box. E.g. I get students to digitise clumps of trees around Mt St Helens and give them a percentage tree cover value. Put all the polygons in a folder then save the folder as a KML file.

2] Go to the fusion tables site. If you do not already have a Google account you will need to set one up.

3] Click on File > New table > Import data > From this computer > Choose file, then upload your kml file. Click next then check the import columns include a 'description' column before clicking 'next' again to accept. Write a relevant description in the ‘Description’ box presented, then click Finish.

4] Your data should appear in a table with columns for description, name, and geometry. The Geometry column is the data Google Earth uses to draw each polygon, click on one of the kml labels to see the list of lat longs it uses.

5] Click on Visualize > Map. Your polygons should appear in a mashup using Google Maps, select ‘Satellite’ top right to see the true terrain. You will notice they are a default red at present. To create a simple thematic map we will apply a palette to the polygons colouring them a different colour depending on the percentage cover entered in GEarth.

6] Click on Visualize > Table to switch back to table view. Select Edit (on the menu bar) > Modify Columns > description > Type > Number > Save. This changes the percentages you entered in the GEarth description balloons from text to numeric values and you will see the description column right justify itself as a result.

7] Switch back to map view, now select Configure Styles (on the top of
the map) > Polygons, Fill colour > Buckets

Click the Radio button and on the pull down menu select 5 buckets. Select Column > description.
8] By default you have been given equal sized buckets (20% each), change them if you want. You should change the colours in the pull down menus on the right of the dialogue box to something appropriate. Click Save to apply this palette.

You should now see your palette displayed.

9] Now you have set up your VGI system, add others to the fusion table (share button top right of your fusion table web page > choose collaborators who can edit).

10] Get your volunteers to complete step [1] then access the fusion table and choose File > Import more rows to upload their own polygons.

Viola! A basic VGI system.






1 comment:

Juan Carlos Sierra R said...

Fusion tables is one of the best tools that Google has removed the kml interaccon of data is essential in studies of geographic information, some time to develop an example with data election in the city of Barcelona - http://juanchosierrar.blogspot.com/2011/02/mapas-de-geomarketing-electoral-de-las.html -, to prepare various thematic maps to polling data and integrate fusion data in tables (although some time was a little fresher than now), there is also a good example of my city which is developing an inventory of trees and was also posted on fusion tables(http://juanchosierrar.blogspot.com/search/label/Pereira%20%28Colombia%29). Excellent tool, but need to improve more.

Congratulations. Excellent site