Karen Steede-Terry’s book ‘Integrating GIS with the global positioning system’ provides an inside track on the use of both high-end and consumer GPS systems. The book follows the usual ESRI format, with profuse illustrations and examples from a variety of industries and projects. What comes through most clearly is Steede-Terry’s know how - such as the caveat on the usage of consumer GPS systems.
Snapping
These are often sold for use inside an automobile and may perform some serious processing to the data – such as snapping the GPS location to the nearest road, or interpolating the location when there is no signal – like in a parking garage. For Steede-Terry, differential GPS is the ‘revolution within the revolution’ and is the secret to highest accuracy. Post processing the GPS signal is required for the best results. GPS vertical accuracy is always limited due to the fact that satellites, by their nature tend to be high up – limiting triangulation accuracy in the vertical plane. Real-time differential sources are available in the US from organizations like the US Coast Guard.
Accuracy
The choice of GPS receiver depends on your business requirement. If you are after readings in the 1-5 meter range, an inexpensive handheld model will suffice. For sub-meter accuracy, a high-end backpack model, or laptop-connected unit is required. Before rushing into the field, Steede-Terry advocates building a data dictionary of standard nomenclature for features that will be captured in the field. This can be quite a sophisticated data structure, tailored to the problem in hand and loaded into the field unit. Some systems even allow field editing of the dictionary – at the risk of inconsistency and synchronicity issues.
Duke Energy
The book includes a variety of case histories including Duke
Energy Field Services’ use of GPS/GIS to validate conflicting map sources over
its 50,000 mile pipeline network, 80% of which was acquired through acquisitions
and mergers in the last 5 years. Steede-Terry’s insight is unfortunately diluted
in the short book by a plethora of illustrations. The bewilderingly wide range
of case histories from ESRI’s marketing department take up space that could
have been better used explaining the technology.
Integrating GIS and the Global Positioning System.
ESRI Press. ISBN 1-879102-81-1.
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