Handhelds for high-accuracy GIS data collection
(by Conrad H. Blickenstorfer)

The Trimble Geo handhelds are affordable, all-in-one mobile GIS solutions running Windows Mobile 5.0 on a 416MHz Marvell PXA270 processor. They offer large 512MB onboard Flash storage which can be supplemented via SD cards in the sealed SD slot. With a footprint of 3.9 x 8.5 inches and being about 3 inches thick, the 1.75 pound Geos are relatively large and heavy for handhelds. That's because they are not only rugged, but pack a large full-shuft battery, as well as fully integrated GPS receivers and antennas.

These being Trimble devices specialized for mapping and GIS applications, GPS performance is first rate. The units differentially correct location in real time by using corrections from satellite-based augmentation systems such as WAAS or EGNOS. They can also use their own internal Bluetooth radio to connect to a dedicated Trimble GeoBeacon receiver.

The Trimble Geo comes in three varieties, the GeoXM, GeoXT, and GeoXH. They are technologically the same except for the performance and accuracy of their internal GPS circuitry. The GeoXM is an affordable solution that delivers 1 to 3 meter accuracy. The GeoXT is geared towards maintaining precise GIS databases by delivering sub-meter accuracy. The GeoXH, finally, is Trimble's top-of-the-line solution for high accuracy GIS data collection. By using H-Star technology, the GeoXH delivers sub-foot accuracy. Add a Zephyr antenna, and the GeoXH becomes accurate to eight inches.

Like all Trimble handhelds, the Geo series can be used with TerraSync software, the Trimble GPScorrect and GPS analyst extensions for EXRI's ArcPad. There is also GPS Office software and a SDK for it.