Thanks for the links! I tried to download some of the files containing the state and county boundaries, but they are too huge (several dozens of Mb). I need something substantially less fine-grained. Say, if each county's boundary is rounded off to a 30-point polygon, with each vertex taking 26 characters to encode (11 digits for latitude plus decimal dot, same for longitude, a comma in between latitude and longitude, then a semicolon before the next lat/lng pair), and there are 3100 counties, then it'd take around 2.3Mb of plain text data. Do you know where I can get such coarse-grained data? If I can get my hand on such data, then I'll make a widget that anyone can use to plot any sort of U.S. county or state level data. I think it'll be fun, with all that "open government" / "open data" efforts going on.
David John Callahan wrote: > You can get U.S. state and county boundary data files from various > places. Here are a few. The most common GIS data format is called a > "ESRI shapefile" which has been around for about 15 years or so. There > are plenty of packages out there that can read/convert shapefiles. (For > command line, programmatic use, check out GDAL.OGR, > http://www.gdal.org/ogr/) > > > /The National Map/ Seamless Server > http://seamless.usgs.gov/index.php > (if you can figure out how to use it!) > > The National Atlas > http://www-atlas.usgs.gov/atlasftp.html > > U.S. Census Bureau TIGER files > http://www2.census.gov/cgi-bin/shapefiles/national-files > > U.S. Census Bureau Generalized boundaries (smaller file sizes, less > accuracy) > http://www.census.gov/geo/www/cob/bdy_files.html > > Geospatial One Stop (large repository of US GIS data and map services) > http://gos2.geodata.gov/ > > > Note that there are tons of vertices with state or county level data. > There are about 3100+ counties. I've seen Google Maps struggle (polygon > overlays) with only hundreds of polygons at lesser resolution. So, KML > or straight coordinates wouldn't help much here. However, a flash widget > or served from a map server would be fine. > > - John > > > > > > David Huynh wrote: > >> John Callahan wrote: >> >> >>> Regarding the last point, I agree that it's difficult to see which >>> direction to go. >>> >>> >> Yes,... other people have used some of the tools for showing clinical >> drug trial data, rocket test data, educational materials, historical >> events, software development project deliverables, ... >> >> >> >>> There are so many ways to store geospatial, many of which are resource >>> and storage hogs. Imagine having 100 items, each with a URL-style >>> field pointing to WMS services and Image and KML overlays to be >>> displayed on the same map. Performance would definitely be >>> sacrificed. Technically, this doesn't seem to be very hard as Google >>> Maps supports these natively. Even if you integrated OpenLayers (or >>> similar FOSS Geo map clients), these types of overlays can be easily >>> done. Performance and variety of standards jump out at me as the >>> biggest obstacles. >>> >>> On a separate note, what about having a map extension that is similar >>> to Timeplot? For example, you can bring in one CSV file or >>> spreadsheet that contains dozens or hundreds of data points w. >>> location. It could be a 2D array for different types of markers (like >>> separate lines on Timeplot) or maybe separate maps (like different >>> bands in Timeline.) >>> >>> >> That would be a good way to go. You will also probably want Babel to be >> able to convert KML files from another domain into Exhibit JSONP. Note >> that Timeplot can only load files (except for JSONP) from the same web >> domain. >> >> By the way, one of the type of geospatial data that I think will be very >> useful is state and county boundaries, starting with those of the U.S. >> For example, >> http://elections.nytimes.com/2008/results/president/map.html >> (switch to "County leaders") is quite an interesting visualization, and >> the NY Times has produced a lot of U.S. maps broken down into counties. >> If you click on a state on that map, it zooms in and you can then select >> each county. I think that kind of map should become a reusable widget, >> for anyone to plot any sort of per county data. Do you know where to >> obtain the boundaries for the counties and states? >> >> David >> >> >> >> > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "SIMILE Widgets" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/simile-widgets?hl=en -~----------~----~----~----~------~----~------~--~---
