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Dr Mike J Smith
Kingston University

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Global Mapper

Sun, 06 Jan 2008

Global Mapper is one of those little pieces of "GIS gems" that many people haven't heard of and should have done. Global Mapper LLC was founded in 2001 and, from what I can tell, rapidly built a following of contented customers around the ability to import and export a vast array of vector and raster formats and visualise DEM data. Not only is it the Swiss Army Knife of file format converters, but it also has very efficient algorithms allowing fast visualisation and analysis of DEM data. And to cap it all off it is inexpensive (~$300) and has technical support direct from the developer that is honestly second-to-none.

So what does Global Mapper do? Well the partial list of supported formats currently stands at 92; if GM doesn't support it then simply ask the develop. And remember it can import and export to these formats. Besides the usual useful list of candidates including all ESRI and ERDAS derivatives, MrSID, JPEG2000 and GeoTIFF, it also includes support for LiDAR (LAS) and KML, as well as live web downloads (e.g. TerraServer). Analytical facilities include live connection of a GPS, inter-visibility, 3D viewing, crop, reproject, merge, digitising, georeferencing, contour generation, triangulation, raster math... the list goes on.

What has really increased the profile of Global Mapper is a strategic alliance with Intermap that allows Intermap access to the source code and distribution to their NextMap terrain customers.

And the support? Well the best place to go is the Global Mapper Forum where the developer is very active. Expect responses to queries posted within the space of minutes to hours. And if it turns out its a bug or minor feature, expect a binary ready to download within 24 hours. For example, I had been loading some large LiDAR datasets (~5 million points or 100Mb) into GM, but it would fail to complete the triangulation of the 3D points. It turned out that the triangulation tried to complete entirely in memory and I didn't have enough space. The developer changed the routine to allow GM to write to a temporary file on disk. Added to this is that forum members get 10% off GM or any updates.

So GM is an excellent toolkit and a GIS lab isn't complete without at least one copy. It isn't a full blown GIS and doesn't pretend to be, but it is fast and have some fantastic capabilities. Note that it *only* uses triangulation to create TINs for the conversion of vector elevation data to raster formats. This may or may not be wanted (from an analytical perspective) and the rasterisation may well need the use of a product like Surfer, or R, round-tripping back to GM.

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