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Archive for March, 2008 Page 2 of 2



The Big List Of Free Basic GIS Programs – A Through H

The backlog of topics for this blog continues to grow beyond my ability to keep up with it, and current work demands make it unlikely I’ll be able to catch up soon (though I should still be able to put up new posts at about the same rate). So I thought I’d do a quick set of posts on various types of GIS software, including both those that I have looked at in some detail, as well as those that I’ve given either a cursory look, or none at all. Let me know which ones I’ve missed, and I’ll add them to the list (and put up a separate post on them if warranted). I welcome comments on any of these programs, especially those I haven’t really posted on yet; if the comment is long enough, I’ll put it up as a full guest post. And I’m likely to come back to some of these in greater detail in the future.

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List Of Map Products From the USGS

Stopped by the USGS Seamless Server recently for the first time in a while, and noticed they’ve added a drop-down list titled “Available Interactive Maps”. Listed there are a fairly wide-ranging set of data resources they’re working on; some are mostly duplicates of the Seamless Server data but with a slightly-different focus, while others contain unique data.

ARMI: A data viewer and retriever for the USGS’s Amphibian Research and Monitoring Initiative, a program designed to study and hopefully slow down the recent drastic reductions in amphibian numbers. Data includes factors like pesticides, hydrography, climate/weather and more.

USGS Projects In Afghanistan: Includes both an interactive data viewer and a list of downloadable data, including:

  • Landsat data, including 6-band corrected imagery by 1:250K quads
  • Aster Level 1A and 1B data
  • SRTM 90-meter DEMs, with void filling
  • German, Russian and USGS geology maps
  • Full sets of Russian topographic maps, 1:50K and 1:200K

U.S.-Mexico Border Environmental Health Initiative: Interactive data viewer for “satellite imagery, orthoimagery and integrated geology, hydrology, transportation, geographical names, potential sources of contaminants, demographic data for population density, Nexrad daily weather, and boundary datasets”.

CEOS WG on Information Systems and Services: A viewer showing coverage areas for various forms of earth observation (satellite and aerial observations). Coverage areas only, no data.

Drought Monitoring: Drought and vegetation index data for the United States.

Elevation Derivatives For National Applications (EDNA): Hydrological-oriented database (30-meter US resolution) with raster and vector data:

  • Aspect
  • Contours
  • Filled DEM
  • Flow Accumulation
  • Flow Direction
  • Reach Catchment Seedpoints
  • Reach Catchments
  • Shaded Relief
  • Sinks
  • Slope
  • Synthetic Streamlines

Integrated Vegetation Mapping Viewer: NDVI (normalized differential vegetation index), Fire Potential, Percent of Average Seasonal Greenness, and more.

MRLC: Focused on the National Land Cover Database (2001 and 1992).

MOPEX: Focused on stream, watershed and hydrological data for the US.

Topobathy: A few small sections of bathymetric shaded relief (e.g. off the coast of San Francisco, the Seattle bay area), but otherwise not much different than the USGS Seamless Server.




Using Google Earth Ground Overlays To Display Shapefile Data

The best way to display shapefile data in Google Earth is to convert it directly into vector KML format, and I’ve covered several ways to do that for free or cheaply, including stand-alone programs and online converters. Of all these options, I prefer using either shp2kml or Shape2Earth because of the flexibility they offer in setting display attributes like color and shape. But there’s another option: convert shapefile data into a raster image, and then display it in Google Earth as a ground overlay. This has a few advantages over vector KML format:

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Beating The Garmin 2025-Map Limit With US Topo Maps

Many recent Garmin GPS mapping units (like the 60Cx and 76Cx units) have a maximum limit of 2025 map sections that you can upload directly to the unit, and you’ll get an error message if you try to exceed the limit. If you try uploading more than 2025 to a microSD card in a card reader, you won’t get an error message, but the GPSr unit will still not be able to display the data from more than 2025 maps after you put the microSD card back into it. This wasn’t such a big deal when memory was expensive, and 128 MB of memory was considered a lot – there was no way you come close to that 2025 limit with that little memory. But these days you can get a 2 GB microSD card for a Garmin unit for less than $20, and you could easily fill such a card with more than 2025 maps if that were possible.

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