1 research outputs found
GPS-aerotriangulation : in observation space
PhD ThesisThe research completed on UPS-aerial triangulation has been focused on combining
of UPS and photogrammetric data in the way using GPS derived antenna coordinates,
so called as "combination in position space". Thus, these antenna coordinates are
used, or replaced with the normal control points on the ground, as control points
which have been moved into the air. It was noticed that it is necessary to use crossing
strips and introduce drift parameters into the analytical aerial triangulation estimation
to compensate the shifts which are seen in these coordinates, probably caused by cycle
slips in the UPS data. UPS offered a good opportunity to supplement, or completely
replace, the ground control required by aerial triangulation procedures by determining
the positions of an antenna onboard the aircraft, at each moment of exposure, quickly,
cheaply and accurately but with crossing strips, drift parameters and stand-by GPS
data, postprocessed GPS data as UPS derived antenna coordinates.
This thesis offers a new method which is based on a combination of GPS dual
frequency phase observations and photogrammetric measurements in a bundle
estimation process, so called as "combination in observation space". Thus the new
method leads to the solution of the redundancy problem facing the GPS users if the
ambiguities and the point coordinates (or coordinate differences) together with the
other parameters are to be solved for simultaneously. It also removes the need for
cioss strips to compensate for shifts in the antenna coordinates and provides a good
basis for the determination of integer ambiguities and cycle slips thereby saving a lot
of effort and time. To explain this concept, the thesis reviews the UPS double
differencing processes based upon phase observations and analytical aerial
triangulation estimation method with emphasis being laid upon estimation using
bundles. Alongside these, error sources that are likely to affect the UPS and bundle
measurements are discussed and the new combination method is explained. The
ability of the combined system to solve for the perspective center coordinates and the
attitude of the camera onboard the aircraft, the coordinates of object points and integer
ambiguities and to determine cycle slips in the way it propagates several random
errors were the focus of the simulated tests carried out. The tests revealed the high potential of the combined system in relation to this. Although the system may be
regarded as a reasonably sensitive method to solve for these parameters
simultaneously as there are some cases where some of these parameters, especially
integer ambiguities, cannot be solved for correctly or cycle slips cannot be detected.
This is thought not to be a disadvantage of the method itself, but is rather due to weak
geornetly or insufficient observations with the small sample used.
The main conclusion from this work is that a combination of GPS and
photogramrnetiy is indeed possible in observation space. The advantage in that cycle
slips and integer ambiguities can be solved for (i.e. photogrammetry is contributing to
GPS - not just the other way around as in the usual case) and additional
photogrammetric data (in the form of cross strips) is not needed. The method has been
to be successful even in the presence of severe multipath (up to 5 cm).Turkish governmen