04 December 2006

Thematic Google Map Creator

University College London (UCL) has been very busy and using their resources have made an excellent thematic mapping package for overlaying on google maps.

UCL - London Thematic Mapping on Google Map

The Google Map Creator is a freeware application designed to make thematic mapping using Google Maps simpler. The application takes a shapefile containing geographic areas linked with attributes and automatically generates a working Google Maps website from the data. It does this by pre-creating all the necessary files and saving them into a directory. Publishing the map on the web is then just a matter of copying files onto a web server, allowing Google Maps to be used with the majority of ISPs, including Google Pages.

UCL - World Thematic Mapping on Google Map

"How It Works?
A shapefile is loaded into the application and displayed on the screen. A projection file (.prj) MUST be included with the shapefile, otherwise the data cannot be placed in the correct position over the Google Map. This file is easily created externally if needed. The displayed attribute, colouring of the data, geographic extents and maximum zoom levels are defined by the user. Colouring is achieved by setting colours and thresholds for values in the attribute data e.g. any region over 1.0 is red. The application shows how many tiles will be created, which can be changed by altering the maximum zoom level slider or by limiting the geographic area. When the create button is pressed, the result is an html page and a directory containing all the required Google Maps tiles. As all the tiles are pre-created, all that is required to publish the map on the web is to copy the html page and the tile directory onto a web server, making sure that the Google Maps API key contained in the html file is correct for the site. This allows the publishing of data on 'Google Pages' or any other ISP. The html file is created from a template, but only a limited knowledge of Javascript and html is required to create a completely new design from scratch. This can be done by cutting and pasting from the automatically created template.

The main problem with creating Google Maps sites in this way is that the number of tiles can be very large. The application manages this problem by allowing the user to control the maximum level of zoom and the extents of the geographic area. For example, with a map of worldwide Gross Domestic Product by country, there is no point in zooming in beyond the point where one country fills the whole screen, so the maximum level of zoom is limited and the number of tiles kept within a manageable level. In this example, six zoom levels are adequate for the data, resulting in 962 files occupying 5MB on the disk. At the other end of the scale is data from a GPS tracked carbon monoxide sensor used within a 1KM grid square in London. In this case, the maximum zoom level is used to show the 5 metre data grid, but only 71 files (less than 1MB) were created as the geographic area is so limited. "

Download available from the UCL website

Excellent Work UCL - Mapperz

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At Monday, December 11, 2006 6:26:00 pm, Anonymous Anonymous said...

Would be great if they developed such an app using OpenLayers instead of Google Maps...

At Wednesday, December 13, 2006 11:06:00 am, Anonymous Anonymous said...

An advantage of Google Maps is that it already has large scale background data (ie streets in many cities), which can be used as a backdrop to, for example, the street level polution data shown in the example


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