I’m posting about the University of Maryland’s Global Land Cover Facility, a massive archive (13 terabytes and growing) of various kinds of satellite imagery and derived data, even though I suspect many readers of this blog are already familiar with it. Most of the data is freely downloadable, accessible through a browser-based interface, and georeferenced for use in GIS and satellite image analysis software. Images are typically at moderate resolution (15-250 meters per pixel); free access to Ikonos high-resolution imagery is available only to NASA-affiliated researchers. For multi-wavelength data, you can usually download separate images for every spectral band as well as composite images.
Direct satellite imagery includes:
ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer))
- L1B Imagery (three different sets of IR imagery at various resolutions, covering the spectral range of 0.52-11.65 microns)
Landsat (Multiple bands, visible and IR, at 15-60 meter resolution from all Landsat missions)
- GeoCover
- Landsat ETM+
- Landsat MSS
- Landsat TM
MODIS (Moderate Resolution Imaging Spectroradiometer) (7 bands covering the visible and near-infrared ranges)
- 32-day Composites
- 16-day Composite
There are also many datasets derived from the multi-spectral satellite imagery and data from the Advanced Very High Resolution Radiometer (AVHRR).
The Map Room posts on GeoGratis, the Canadian Government’s new web gateway for free geographic data, both raster (topo maps, satellite images, etc.) and vector (hypsographic, political, etc.). No DEM (digital elevation model here), but you can get 90-meter data for Canada from the Geobase website or the USGS Seamless Server.
Doc Savage’s Old Word Archaeology website (great name!) has links to maps aerial/satellite photos, and vector data for most of Israel and Jordan, with some data for surrounding areas (mainly Syria and the Sinai); click on the links under “Digital Data” on the right. Most of the data is georeferenced for direct use in GIS software. Data includes:
- 1:50K topo maps; sources are US and Soviet military topos, and Arabic topos. See this post for more info on Soviet military topo maps.
- Landsat 28m resolution imagery
- NIMA-SPOT 10m panchromatic (black and white) imagery
- Digital Chart Of The World (DCW) data by country, including topography (hypsography), populated places, land use/land cover, transportation, drainages, cultural places, utility lines, and airports. This data dates from the early 1990s (essentially VMAP0), but is still useful. This vector data is in ArcInfo coverages; see this post for info on how to convert ArcInfo coverages into shapefiles.
A while back, I posted on an NOAA website that mapped carbon dioxide concentrations and emissions globally and locally. The Green Car Congress website has posted about a new resource that has maps of both emissions and sequestration, real and potential, for the US and Canada.
One site linked to has PDFs of the printable version of the Carbon Sequestration Atlas of the United States and Canada. The NatCarb site links to maps, static and interactive, showing both the sources and potential sinks/sequestration sites for carbon dioxide.
If you love maps, you have to see the Strange Maps blog. Unusual, historical, fictional, gastronomical, delusional, exceptional, etceteral maps, with excellent accompanying posts (and great comment sections as well).
1/12/2010: Unfortunately, the latest versions of the TatukGIS viewer have removed the “Export To Image” function, which was the most valuable function of this program. So I can’t really recommend it anymore; you’d be better off with a free GIS program like qGIS, MapWindow or MicroDEM, which do offer raster combination and export functions, albeit without the same degree of control as the older version of TatukGIS Viewer. If you look around online, you might still be able to find the older version somewhere.
The USGS Seamless Server data gateway I posted about yesterday has a filesize limit per download of 250 MB uncompressed (the zipped, compressed size of the downloaded files is usually much smaller than the uncompressed size). If raster map data you’ve selected for download has a combined size greater than 250 MB, the server breaks it up into smaller segments, each downloadable as a file. If you import all of these separate files together into a GIS program, it will automatically position all the pieces together in the right place. But you might find it more convenient to combine all of the individual pieces together into a single map file with the same resolution, and still georeferenced.
Continue reading ‘Full Resolution Raster Map Combining, Subsetting And Export With The TatukGIS Viewer’
Over the next few weeks/months, I’ll be putting up a fair number of posts on software tools that work with Digital Elevation Models, or DEMs for short. A DEM is essentially a grid of an area where each point in the grid represents the elevation or altitude at that point. With a DEM, you can do things like determine the altitude and slope at a point, measure the terrain profile, make 3D views (both static and interactive), and so on. Before starting those posts, it makes sense to talk about a good source for that data.
Continue reading ‘The USGS Seamless Data Distribution System’
The Moderate Resolution Imaging Spectroradiometer (MODIS) is a low-to-moderate resolution multi-spectral imaging system currently in operation aboard two NASA satellites, Terra and Aqua. Both satellites are acquiring imagery on a continuous basis, and NASA has created a website that allows access to near-real time georeferenced imagery from both satellites, as well as archived imagery from previous days.
Continue reading ‘Near-Real-Time Georeferenced MODIS Satellite Images From The Terra/Aqua Satellites’
