Creating custom Google Map tilesets

Based on a few questions coming in through Cartotalk over the past few months, I’ve decided to look into offering some services around the creation of custom Google Map tilesets. This is in effect and extra layer with any georeferenced data you like, appearing inside Google Maps, running on your own website.

Global Mapper, which I’ve raved about before, offers a nifty way to export any georeferenced raster image to a Google Maps tileset, it will even generate the html and javascript for you. Unfortunately, in the case of maps it’s generally not a matter of pressing a button and it will magically work. There’s a few things to keep in mind and those are the things I hope to add value to my customers with.

  • Resolution
  • Projection
  • Design for screen, rather than print

Basically it boils down to making sure the image that is read by Global Mapper is as close to the correct projection and resolution as possible, to avoid resampling. I’ve put a few samples online on the Red Geographics website.  As always, feel free to contact me if there’s questions.

In addition to the design, another important thing to keep in mind is the optimization of the images. I’m partnering with Derek Tonn of GraphicsOptimization for this. It’s amazing how much smaller he can squeeze the images and still have them look the same (at least to the naked eye). A 20% reduction in the case of b/w aerial photography for example (not bad if you consider the 2 sets together weighed in at 120 Mb before optimization). This saves time, energy and ultimately, money.


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