Tracking city growth
June 12th, 2007 by JTJ

Once again, O'Reilly's Radar tips us to a fine posting related to JAGIS (Journalism and GIS), this one regarding the challenge of generating change-over-time in urban areas.

Stamen's Map for Trulia

Posted: 12 Jun 2007 12:22 AM CDT

By Brady Forrest

stamen map

Trulia's new Hindsight Map is a beautiful, animated visualization of the development history of US cities and towns. With it, you can watch entire towns and cities grow. In Seattle, you can watch the city grow starting in year 1900. Trulia is a real estate search engine (much like Zillow). Stamen Design, known for their work on CabSpotting and in Digg Labs, built the map for Trulia using their new Flash mapping library, Modest Maps. Tom Carden and Shawn Allen of Stamen released and demoed Hindsight at Where 2.0.

Tom sent me the following notes on Hindsight and Modest Maps:

  • The use of our Flash mapping library (Modest Maps) means we can change the brightness/saturation of the maps, so the data is easier to read
  • The use of Flash 9 specifically means we can throw around *much* more data than is currently possible with AJAX approaches (thousands of points in real-time – none of the data is pre-rendered)… a Silverlight port of Modest Maps is in development, by the way
  • The URL in the address bar always represents the place you're looking at, using the location fragment (hash), so links can be easily passed around by IM, email, blogs etc.
  • The data coming from Trulia is ordered using a random number for each property, so we can always show a sample of properties when zoomed out, without having to do aggregated/generalized views of the point data (Trulia already do this well with their own heatmap product)
  • The flash piece in the blog header grabs the blog's RSS feed and finds links to the visualisation – the lat/lon is in the URL – and plots them on the map
  • Modest Maps is almost ready for a 1.0 release and we're keen to get people familiar with Flash development to test it out. There is code that's capable of loading Microsoft, Yahoo and Google map tiles as well as OpenStreetMap, NASA Bluemarble and more, for Flash and Flash Lite in Actionscript 2, Flash 9 and Flex in Actionscript 3, as well as an ongoing Microsoft Silverlight port.

Time has been one of the missing dimensions in online maps, but recently it has become a common thing to add. (Radar post) recently added the fourth dimension with their ability to track geographic stories over time. Google Earth (info) added the ability to “play” GPS traces. Hindsight really has me wondering about the applications of time-phased maps beyond analysis. In situations like Katrina (See Mikel Maron's post on the maps of Katrina) and the Maze Meltdown (See SF Chronicle article on the Maze) where there are rapid changes to roads this would especially helpful. To get your mind around changes, you need to be able to compare. I wonder if we can expect this to come from the major portals.

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