ASSESSMENT OF TOPOGRAPHIC MAPS PRODUCED BY DIGITAL PHOTOGRAMMETRIC WORKSTATION

Topogeaphic map can be considered as an essential initial product for most of large
engineering projects. Hence, increasing the efficiency and quality of these maps is a
main issue of any surveying works. Many methods are considered in the production of
topographic maps, according to the required accuracy, available instruments,
afforded time, and involved personnel. The history of topographic map production by
photogrammetry is not very old, only about half a century, due to its great efficiency
and advantage especially in inaccessible and mountaneous areas. Today,
photogrammetry has been vastly broadened to include the use of data from sensors
utilizing other portions of the electromagnetic spectrum, in additional to the
conventional photography, for many applications. Also, as a result of the rapid
development of computer technology and software, assessment of the accuracy of the
topographic map produced by applying the principle of digital photogrammetric
workstation is the main scope of the current investigation.
In order to achieve this objective, aerial panchromatic photos have been taken at a
scale of 1:15000 for a certain hilly study area, and scanned at different resolutions.
Leica photogrammetry suite (LPS) digital software was used to perform this work
with reasonable accuracy. The final resulted values as discrepancies of some selected
check points, root mean square errors, total image unit-weight RMSE, and standard
deviations of the automatic generated tie poits shows that 2117 dpi resolution , which
equivalent to an image coverage 12 μm, gives the less error values than the other
adopted resolutions and with an absolute optimistic accuracy. In addition, the
topographic map, presented as a layer of spot points, resulted from this resolution will
be compared with the available base topographic map for the same study area
produced from analytical stereoplotters device, by using special map projection
software for unifying the coordinates of both analytical and digital map. From this
comparison, it can be found that, about 75% percent of the resulted points passed on
contour’s reference topographic map, which indicate the efficieny of the topographic
maps produced by digital photogrammetric workstations.