A useful collection of links to map symbols is the Unofficial Arc/Info & ArcView Symbol Page. While some of the links are strictly for ArcView palettes and ArcInfo line and marker sets, a fair number link to graphic symbols and TrueType Fonts useable in any compatible GIS or mapmaking software. Symbol sets cover a wide variety, including roads and highways, geology, and animals. Most, but not all, are free. Also check out the links at the bottom of the page to free clip art resources.
Archive for the 'GIS' Category Page 18 of 23
As you might guess from the name, MicroDEM is a program that works with digital elevation models (DEMs), plots of elevation as a function of position, the same kind of data used by 3DEM. But MicroDEM contains far more features and capabilities than 3DEM, and includes other non-DEM related features as well. I like to think of MicroDEM as a “Swiss army knife”, since it contains so many interesting and useful tools. Even if you’re not into GIS, MicroDEM is worth looking at for its terrain visualization and analysis capabilities. I could post for month or two on just MicroDEM alone, and by the time I’m done, the posts will likely add up to at least a month’s worth. But to start, I will do a number of posts over the next week or so on just a little of what MicroDEM can do. Bear with me on the first few – I have to get through some of the basics of program installation and operation before I can get to the really cool stuff.
Continue reading ‘MicroDEM: A Swiss Army Knife Of Terrain And GIS Tools’
Other mapping sites seem to be doing an Earth Day related post, so I’ll move this one up a bit. Energy production from the heat of the earth (geothermal energy) generates no carbon dioxide emissions that contribute to global warming, and could produce as much as 100,000 megawatts in the US alone by the year 2050. Here are some websites with geographic geothermal data, both maps and downloadable data.
A handy source of world vector data, the National Geospatial Agency’s VMAP0 vector data from 1992/1993 has been converted to E00 format and issued as the Digital Chart Of The World. While more recent VMAP0 data is available from the NGA (and even higher-resolution VMAP1 for some areas of the world), it tends to be in the VPF format, which many GIS programs don’t read. While it may be a bit older, DCW data is readily available in E00 format, which many GIS programs can read directly, and it can be converted to shapefile format for compatibility with virtually every GIS viewer and editor.
Penn State maintains the Digital Chart Of The World Server, which offers up DCW data in E00 format by country (and in some cases, e.g. Brazil, Canada, and Australia, by state). Data available includes:
- Political/Ocean (Point)
- Populated Places (Polygon)
- Populated Places (Point)
- Rail Roads (Line)
- Roads (Line)
- Utilities (Line)
- Drainage (Network)
- Drainage (Point)
- Drainage Supplemental (Point)
- Hypsography (Network)
- Hypsography (Point)
- Hypsography Supplemental (Line)
- Hypsography Supplemental (Point)
- Land Cover (Polygon)
- Land Cover (Point)
- Ocean Features (Line)
- Ocean Features (Point)
- Aeronautical (Point)
- Cultural Landmarks (Point)
- Cultural Landmarks (Line)
- Transportation Structure (Line)
You can download the digital vector data directly, or view a GIF preview of the data individually or collectively. Most data is in geographic format (latitude/longitude), with the notable exception of Russia in Lambert Conformal Conic. While the documentation states in one place that the spheroid is the Clarke 1866, it appears from other references that the data is actually in WGS84 datum.
Once upon a time, LizardTech, the owners of the Multiresolution Seamless Image Database (MRSID) compressed image technology often used with satellite and aerial imagery, had a free stand-alone viewer available on their website. Using this viewer, you could open full MRSID images, and export re-sampled subsets as TIFF images, GeoTiffs if the MRSID file was georeferenced or came with a world file. But LizardTech dropped the link for that stand-alone viewer download from their website some years ago, and now they only offer a browser plug-in that only allows viewing of MRSID images, and command-line utilities that convert the entire MRSID file into what could be an enormous TIFF image file.
But the Internet being what it is, it’s difficult to eliminate a file completely, and there are a couple of locations that still have the stand-alone MRSID viewer available for download. The Library Of Congress has many downloadable maps in MRSID format, and they offer a download link to both the viewer install program and the PDF manual (there’s also a viewer and manual available for Macintosh OS 9.x). The Spatial Analysis Laboratory of the University Of Arkansas at Monticello also has the install program, along with a downloadable PDF lesson on how to subset a georeference MRSID file and export it as a GeoTiff.
You can also use the free TatukGIS Viewer (Windows only) to open, view, and export MRSID files as well.
There’s a bit of cognitive dissonance in posting about free toolsets for a program that costs well over $1000 if you buy it new. Still, I’m guessing that a fair number of visitors to this site use ArcGIS, and may not be familiar with some of these. There are also free tools available from the ESRI support site as well.
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.