Coupling 3D GIS-based Modelling and Field Methods to Evaluate Landslide Hazard Predisposition
found at GIS and Science – a great resource for recent geospatial research (papers, presentations, abstracts)
Category Archives: Information
Google Earth downloaded over 1 billion times
Google’s LatLong blog announced Wednesday that Google Earth products have been downloaded over 1 billion times. There are some interesting stats and useful links in the post.
Color selection help
Color selection for maps can be a time-consuming activity. Computer monitors use additive colors (combinations of red, green, and blue) to create different shades, and monitors are backlit, using transmitted light to convey colors to the viewer. Printed maps, on the other hand, use subtractive colors (most often cyan, magenta, yellow, and black inks) to remove portions of white light reflected back to the viewer.
The main effect of these differing methods for producing colors is that hues you select on the monitor often look very different when printed out in hardcopy. This problem is compounded when different computer monitors or printers are used, as colors you were happy with can change dramatically when viewed or printed on different hardware.
Fortunately, a tool exists to help with choosing a set of colors for a map. ColorBrewer was developed by Cindy Brewer and Mark Harrower of Pennsylvania State University. It is an interactive, web-based tool that allows the user to 1) select the number of color classes needed, and 2) choose color schemes appropriate for numeric data (sequential schemes), numeric data with positive and negative values (diverging schemes with a neutral color in the center and darker colors at the extremes), or nominal data (qualitative schemes).
The color schemes in ColorBrewer were tested with subjects with color-impaired vision. You can choose to use only “color blind safe” colors, as well as “print friendly” and “photocopy-able” colors, though these choices limit the number of color schemes available. The best reason to use ColorBrewer, however, is the colors it provides are easily distinguished from each other.
ColorBrewer provides color information usable in several different coding systems (RGB, CMYK, and Hexadecimal) so it is useful for more than just colors for maps in a GIS. The values for your ColorBrewer color schemes can be exported to an Excel spreadsheet, and there is a plug-in tool for ArcGIS available. It is very user-friendly, but has excellent online help if you need it. Check it out!
Citing geospatial data
A common question that arises when writing a paper, thesis, or dissertation, is “How do I cite maps or spatial data”? I have cobbled together some examples over the years, found at various locations on the web, into a web page. Some of the source sites are no longer available (except perhaps at the Internet Wayback Machine), but the sources are still listed on the web page below.
A number of examples were drawn from: Cartographic Citations: A Style Guide, MAGERT Circular No. 1. Chicago: American Library Association, 1992. Thanks to the original authors of this publication.
See this page for my list of geospatial citation examples. I will update these examples as time permits.
The Michigan GeoRef coordinate system
Spatial data provided by the State of Michigan is distributed in a Michigan-specific projected coordinate system named Michigan GeoRef. The type of map projection is known as “Hotine Oblique Mercator”. This coordinate system uses NAD1983 as the datum, but the coordinates are unique to—and usable only in—Michigan. It is supported by ESRI software (ArcGIS) as well as DNRGarmin, which can use the ESRI projection information. The POSC code for NAD 1983 Michigan Georef (meters) is 102123.
In ArcGIS (Version 9.2, 9.3, and 10) the projection information (.prj) file can be found in Coordinate Systems : Projected Coordinate Systems : State Systems : NAD 1983 Michigan GeoRef (Meters).prj
In ArcGIS (Pre-version 9.2) the projection information (.prj) file can be found in Coordinate Systems : Projected Coordinate Systems : National Grids : NAD 1983 Michigan GeoRef (Meters).prj
More information on Michigan-specific coordinate systems is available from either Michigan State University or from the Michigan DNR
All about this site
This web site exists to disseminate information about Geospatial resources at Michigan Tech. In the near future it will contain information about software and data resources at Michigan Tech, plus tips and tricks for using geospatial software, as well as news about available training and recent research related to Geographic Information Science (GIS, or Geographic Information Systems, and GPS — Global Positioning Systems).