Mapping accident statistics

November 21, 2009 3:13 PM

Cartography/Google Maps: I want to represent severity of accident data on a map to show the most dangerous parts of town to walk/bicycle. I have the raw data, but I can’t seen to show the info in a compelling way.

I think a heatmap might be the way to go, but the resources I found on the web didn't really pan out.

Here's a sample from the large data set (3 years worth)
Address City State Date Severity type victim lattitude longitude
1000 Wells Branch Austin TX 1/1/2007 2 MC ROR 30.432663 -97.652927
14300 I 35 N SB Svc Rd Austin TX 1/2/2007 2 MV MC 30.433723 -97.670259
Spicewood Springs & Mesa Austin TX 1/2/2007 1 MV BI 30.383473 -97.771104
1800 Houston Austin TX 1/3/2007 2 MV BI 30.328691 -97.739302
3200 Davis Austin TX 1/4/2007 2 MV BI 30.192833 -97.836974
400 7th E Austin TX 1/4/2007 3 MV PED 30.268062 -97.73886
10200 Brownie Austin TX 1/4/2007 2 MV PED 30.367016 -97.684888
Congress & Lessin Austin TX 1/5/2007 4 MV PED 30.22589 -97.762299
Medical & 37th Austin TX 1/5/2007 2 MV PED 30.30459 -97.744539

Severity ranges from 1 to 4 where 1 is no injury to 4 is fatality, so the latter should show "stronger"

posted by lrivers to technology (8 comments total)

I like maps and I like bicycles, so if you memail me I can generate a raster (or heatmap) that you should be able to overlay in google earth using ArcGIS. I think if you want to put this on googlemaps it uses a lot of memory; so it might be better to have it in vector format (I'm not too familiar with the google map overlay aspect).

However, if you are interested in the process itself, I'm not sure what free resources are available for this specific task (heatmapping). One way of displaying, and examining the spatial statistics can be done in a free program called Geoda.
posted by a womble is an active kind of sloth at 3:24 PM on November 21, 2009 [1 favorite]

One similar map I saw for San Francisco had bigger red circles at the intersections where more collisions occurred.
posted by bottlebrushtree at 3:49 PM on November 21, 2009

How about something like this Calgary crime map?
posted by fish tick at 3:55 PM on November 21, 2009

I too like bicycles and maps! But, what's your question, exactly?
posted by bellbellbell at 4:27 PM on November 21, 2009

A heat map is the best way to go, I think. Are you asking if there are heat map resources other than the ones you found on the web that didn't pan out (what about this one?), or if there are any other ways to map it? I mean, you could map severity just by the colour of the pushpin, but that's pretty rudimentary. Not that rudimentary won't work in a pinch. Take it a step further and you can represent severity by custom icon (size, colour, intensity).
posted by mcwetboy at 4:46 PM on November 21, 2009 [1 favorite]

if you have to use gmaps (or really want to), maybe using the API to import could help.. the docs are at: http://code.google.com/intl/it/apis/maps/documentation/services.html ; im not sure but i think you want to do reverse geocoding.
Don't know if you can place objects of arbitrary size though.
have you tried doing a quick scatterplot of the lat lon data in excel or R ? seeing some early results might give you more ideas..
posted by 3mendo at 4:55 PM on November 21, 2009

I'm not sure exactly what you're asking, but Cartographer.js may help with the visualization.
posted by null terminated at 5:14 PM on November 21, 2009

I'll agree w/ womble on this. Convert the raster to vector and export the resulting .shp to kml polygons. You can always fiddle with transparency once you bring them back into GE. The process to properly georeference & overlay rasters (especially e.g. photos or DEMs) in GE is still(!) sucky, although 5.x is better.
posted by Emperor SnooKloze at 7:19 AM on November 22, 2009