Earlier posts in this series covered online map projection viewers, the best of which is the Brazilian Map Projections Java app. As an interactive learning tool, that one is hard to beat, and the stand-alone map projection viewers don’t match up to it in that regard. But each of the stand-alone viewers I’ve found has useful features that aren’t present in the online map projection viewers.
The first one I’ve looked at G.Projector, produced by NASA’s Goddard Institute For Space Studies (GISS). It’s a Java app, with specific versions available for Windows, Mac, and Linux. Download the file, and unzip the contents into their own folder; in the case of the Windows version, there’s an executable file called G.Projector.exe that starts up the program.
This program’s only significant function is to display different projections in a fairly static fashion, but does a good job at that. You can choose from 72 different map projections, and have them displayed immediately above, with adjustable graticule colors and opacities. It comes with your choice of three Earth map images, and one Martian image, to display. You can also use your own image for the map, as long as it’s equirectangular (i.e. geographic/Plate Carree projection, with latitude and longitude having the same scale), centered on the Prime Meridian (0 longitude), and has no border. The help file cautions against using a large image like the NASA Blue Marble at 5400 x 2700 pixels, saying it will slow down the app or even cause it to hang. But I used a 5400 x 2700 Blue Marble image, and noticed only a very minor slowdown in program operation even with a modestly-powered computer and graphics card.
The program also comes with line continental overlays for the Earth and Mars, but I found these to be of minimal value with the images that come with the program. Overlays are in the CNO format, a list of lon,lat pairs, with separate regions (continents) delimited by the value 9999, so you could make your own if you had the patience. Alt-click on the map, and the latitude/longitude of the point will be displayed; shift-click, and the map re-centers on that point or longitude. Map images can be exported in the PNG, GIF, PDF or PS formats.
That’s all it does – take an equirectangular map image, display it in different projections, and exports the image. Does the job, and is simple to use, but I wish it did a bit more.