Research project AP/07 (Research action AP)
Till the end of the 1980’s, the classical surveying equipment for three-dimensional point localization was the total station, mainly an evolution of a theodolite by adding distance measurement capability, a micro-processor and computer memory to the classical theodolite designed for horizontal and vertical direction or angle measurent. Since the 1990’s, satellite systems have been increasingly used for the precise positioning of reference and detail points.
The use of RTK networks (FLEPOS, WALCORS,…) has boosted the use of GPS receivers for a lot of surveying tasks.
The two techniques (theodolite and GPS) are rather complementary with their own advantages and drawbacks, wich are well documented in literature. As the basic techniques used in both instruments are quite different (satellite radio signals for GPS, opto-magnetic waves for total stations), the original design of both instruments was also very distinct. However, the last decade there has been an evolution towards an increasing compatibility between hardware and software components of both systems and the latest evolution up till now is the combination of a satellite receiver within the housing of a total station, called a satellite equipped or based total station.
As a result, the calibration procedures for classical theodolites should be adapted in order to take this new generation of total stations into account. Logically, the GPS part of these theodolites requires a very specific testing procedure for which the highlines are elaborated further in the project.
The procedures for the calibration of the electronic distance meter (EDM) and the calibration of the angular measurement must also be adapted in order to permit the testing of satellite based theodolites. The software issue is often neglected. However, part of the errors is introduced by limitations inherent to software algorithm implementation, especially when processing satellite raw data. These errors will propagate in whatever computation performed with the inaccurate point coordinates, e.g. computation of areas, traverses, regression,… Therefore, a thorough testing methodology for the controlling software should also be developed.
This proposal responds to the need for a thorough study and valid suggestions for the solution of all the calibration aspects involved with the deployment of satellite equipped total stations, as this type of theodolite will become increasingly popular in the surveying world, in which quality control is an utterly important topic.
Methodologie voor de nauwkeurigheidscertificatie van totaalstations met ondersteuning voor satellietplaatsbepaling : eindrapport
Brussel : Federaal Wetenschapsbeleid, 2007 (SP1797)
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