Mobile GIS technology update

Mobile GIS technology update

GPS and Mobile GIS
GPS is now a standard and widely accepted method of providing position information for a wide variety of user applications, including Mobile GIS. In some locations GPS is the only effective way to map assets in the field. In Japan, for example, GPS-based systems have been used to quickly and accurately define private versus public forestry lands in difficult terrain with few landmarks. The use of GPS in this application allowed the user to achieve the level of accuracy required for the project, within their cost constraints.

Figure 1. GPS mapping of private forestry boundaries in Senbuko East Forest, Japan. Rugged GPS systems provided quick, reliable and accurate performance in extremely harsh conditions.
The key development in GPS technology for Mobile GIS is the integration of a high quality, sub-metre GPS receiver with Microsoft Windows Mobile 2003 software for Pocket PCs, in rugged and cable-free handhelds. This is particularly important for utility companies, where GPS positions must be accurate to within one metre so that field crews can locate manholes, valves, and meters. Accuracy requirements demand the use of professional GPS systems, while field procedures where workers are frequently in and out of vehicles and climbing down manholes, demand the convenience of a handheld, integrated solution.

The quality of a GPS receiver is determined by the architecture of the GPS antenna and receiver hardware, as well as the processing algorithms that operate on the signal. For example, how the receiver design handles electromagnetic interference (EMI) can affect GPS accuracy. All electronic devices emit EMI, which can be thought of as “noise” that “deafens” the GPS receiver. The effect of EMI can be reduced by:

locating the GPS antenna away from the source of EMI
shielding the GPS antenna and/or the EMI source directly, and
using a dual feed antenna and data processing techniques.

Figure 2 illustrates the importance of GPS receiver design, by comparing the performance of a traditional handheld GPS receiver (Trimble GeoExplorer® 3) which does not benefit from advanced antenna design and shielding and a modern professional GPS receiver (Trimble GeoXT™) built using the latest technology advancements. While 80% of positions from the traditional receiver were within 4 metres of truth, 80% of positions from the professional receiver were within 80 centimetres of truth.

Figure 2. Comparison of positional accuracy between traditional and modern professional handheld GPS receivers.
China Unicom, a state-owned corporation tasked with the accelerated development of China's telecommunication industry, has successfully used the advances in handheld GPS to accurately map cell phone towers. Doing this allows mobile phone users more accurate position information directly on their cell phone handsets, supporting the quality location-based services that China Unicom offers customers.

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