January 28, 2011 20:51 by ben
I've put up a map showing the USDA's Major Land Resource Areas (MLRA), Land Resource Regions (LRR) and the COE regions. The map is accesible to all users and the general public at http://wetlandforms.com/MLRAMap.aspx.
A technical note abou the map...
Originally I was trying to create this map using Microsoft's Bing Map API and using ArcMap and Arc2Earth to create a tiled overlay to display the regions. This was working great, but in order to show the entire country at a reasonable zoom level, I would have had to load over 250,000 tiles into a single subfolder on the server. This is pretty difficult to do over FTP apparently, as FTP just does one file at a time. It took about 8 hours to load the first 70,000 tiles and then after that, I ran into some persistent connection problems with the FTP. I suspect that was because there were too many files in that one directory (even though they were all tiny files). My attempt with Bing Map is here: http://wetlandforms.com/PublicMap.aspx. It's a nice map, but since I couldn't load all the tiles, the overlay disappears when you zoom past a certain level. I'll be deleting that whole thing soon, so if the link is dead, that's the reason.
Then I heard about a new product from Google - Fusion Tables. This is a cloud based database system that supports geographic data and has some nice integration with Google Map's latest API. I loaded my MLRA shapefile with Shape Escape and tried it out. Adding the fusion table overlay is just a few lines of code and the results were impressive. I don't know the technical details of how Google does this, but it looks like the server is rendering my layer on the fly, but doing so very quickly (especially fast for a free service). The response time is better than what I've been able to do with ArcGIS Server or GeoServer. It's not as full featured as a dedicated server product like GeoServer. For instance, I can't find a way to label my polygons - so my users will have to click on the map to figure out what region they're looking at. Maybe Google will add that feature in the future.
So anyways, the map is up, enjoy. And Google is my personal hero once again.