(Click here for larger image)The GeoXH handheld is targeted at electric and gas utilities, water/wastewater services, land reform projects, and other applications where accurate positioning is crucial. In recent years, these sectors have experienced increased requirements for subfoot accuracy that until now could only be addressed by long location occupation times or the use of survey grade systems that deliver a much higher accuracy than needed, according to Trimble.
The GeoXH is based on a 416 MHz XScale processor with 64 MB of RAM and 512 MB of Flash memory. An SD card expansion slot provides additional storage. Connectivity options include Bluetooth and WiFi wireless, as well as 10/100 BaseT Ethernet, USB 1.1 client, and serial.
About H-StarTrimble says that its H-Star technology utilizes advances in GPS receiver design coupled with improvements in field and office software to achieve subfoot postprocessed accuracy. Improved antenna design minimizes multipath interference, while advanced noise reduction techniques shield both receiver and antenna from electromagnetic interference from adjacent sources. With the addition of an external Zephyr antenna, eight-inch postprocessed accuracy is claimed possible.
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| PPA Display |
H-Star field software employs a technique called Predicted Postprocessed Accuracy (PPA) that provides a confidence level that the postprocessed data will meet accuracy requirements. The PPA is continually calculated and displayed based on the antenna type, the satellite geometry, the duration of lock on a minimum number of satellites, and the assumption that reference stations used in postprocessing meet H-Star processing requirements. The screen shot here shows a PPA value of 0.21m, meaning that postprocessed accuracy for the current feature should be 21 cm or better.
According to Trimble, postprocessing accuracy depends significantly on the quality of reference stations used, and their distance from the area where data is being collected. Since reference station quality varies, Trimble maintains a list of Internet base providers and major providers such as SOPAC and the US Geodetic Survey's CORS. The regularly updated list includes a "calculated reference station integrity index" ranging between 0 and 100 for each base station.
H-Star postprocessing averages the results calculated from multiple bases. The effect of longer baseline distances can be reduced by averaging with several reference stations in different locations.
AvailabilityThe GeoXH handheld is expected to begin shipping at the end of this month, according to Trimble.
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