Do Crunches Really Work?

Last week, Microsoft released a beta version of a tool called MapCruncher. MapCruncher allows you to take a rendered image (GIF, PNG, JPG) and create a set of map tile layers that can be then drawn over a Virtual Earth (VE) map with the correct projection.

BART Overlay Test ScreenshotSince Redfin’s map is based on VE’s platform, I spent a couple hours using MapCruncher on a test project to see what we could potentially do with it. My project was to take an image of the BART routes in the Bay Area and place it on the map.

It worked out pretty well. A screenshot of the resulting mashup map that was created, or you can just check out the resulting mashup yourself.

What did I learn about MapCruncher?

  1. It’s really easy to use. It provides a side-by-side view of your desired overlay image and a live VE map view. You simply line up landmarks in the cross hairs of each view and mark it as the same location.
  2. It’s pretty quick. I had generated the first version in over an hour and it worked.
  3. Your overlay images need to be very basic and have no text. The original route map image I tried had all the location names and some other features drawn on it. When it was re-projected, the text was completely warped out of shape and unreadable. I used a image editing tool to remove all the text, background colors, etc. – everything except the routes themselves. That simplified route map image considerably cleaned up the resulting mashup.
  4. More landmarks will definitely improve your results. This may seem obvious, but MapCruncher says it only needs around 10 waypoints to render the mashup. I set 10 along the west edge of the map and two on the right. It did great alignment on that left set of points, but the projection was way out of whack along the right in Oakland and Pleasanton. I ended up setting 21 points with an even mix across the different quadrants of the map.
  5. Zoom levels will make you want two source images. I set the render to only go to zoom level 11 first, but didn’t like how soon the route map disappeared when I zoomed in lower. So I cranked it up to render all the way down to 13. Since it’s all doing it from one image, the routes were drawn gigantically at lower zoom levels. I’m guessing you probably need to have different source images for different sets of zoom levels to account for size differences.

Here’s the components of my project if you want to try it out yourself:

MapCruncher seems like its great for either a simple image overlay or a quick and dirty project. If all we had was a rendered image of some information, I could defintely see it as a way to get that data integrated. Honestly, I can’t now imagine trying to generate a set of projected tile layers of it without MapCruncher.

You’ll probably have to spend a fair amount of time getting the overlay images just right so that they work at all zoom levels. You’ll probably want to play with transparency as well to make sure it doesn’t completely obscure the map. At some point, I’ll have to try rendering the image from raw GIS data in a tool like ESRI to see how that improves the results.

You’re probably wondering when this will show up on Redfin’s map. I’m not sure it will. We already display all the BART stops on the map thanks to VE. Adding the route overlays actually adds a lot of clutter to the map without providing a lot more information.

We could certainly be wrong on that though. Drop us a comment if you believe this is very valuable info to add to the Bay Area map or if you have suggestions on what other data overlays we should add to help in your house search.

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