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1:25.000 SCALED PHOTOGRAMMETRIC MAP PRODUCTION SYSTEM
O. Firat*, K.Pamukoglu, O. Eker, Ô. T. Ôzerbil, H. H. Mara?
General Command of Mapping, Photogrammetry Department, Dikimevi Ankara, Türkiye -
(orhan.firat, kadri.pamukoglu, oktay.eker, tuncer.ozerbil, hakan.maras)@hgk.mil.tr
KEY WORDS: Photogrammetry, DEM, Orthophoto, Production System, Automatic Feature Extraction
ABSTRACT:
By applying the latest developments occurring in photogrammetry to the map production systems, important reductions in map
production costs are obtained. For instance, by starting to use digital cameras and GPS/IMU systems in taking aerial photographs and
in aerial triangulation, there is an opportunity of reducing the number of ground control points that must be established due to map
production, film costs, photo-laboratory costs and the scanning costs which are done at sensitive scanners. Whichever way the
development of the map production procedure is aimed, by integrating the new scientific and technological developments in
photogrammetry, especially in automatic feature extraction, into map production systems, the photogrammetric feature extraction
process duration, which is one of the biggest components of map production cost, will be reduced. The operator effect will be lower
and finally the costs will be reduced. In this paper, firstly, the photogrammetric feature extraction steps used in the present 1:25.000
scaled map production process in General Command of Mapping are examined and the production duration and costs are investigated.
In the current production system, feature extraction is done by the operators from stereo models which were created by using aerial
photographs. Extracted features are examined by the operators again for the cartographic and topologie rules and then the corrections
required are done. Thus the photogrammetric production is completed. Secondly, a new alternative system is introduced to reduce the
production duration, operator effect and the costs. In the alternative system, a DEM (Digital Elevation Model) is produced from the
1:25.000 scaled DECM (Digital Elevation Contour Map) of that map. These DEMs are edited on the 3D models and the corrections
are made, streams are extracted and added into the DEM as breaklines. By using these DEMs, ortho-images with 1 m spatial
resolution are produced from the aerial photographs. Also, the contours of the map are generated automatically with 10 m interval by
using the same DEMs and these contours are edited on stereo models and thus auxiliary contours are added. By using the semi
automatic data extraction software, firstly, features that can be extracted from the ortho-images (roads, lakes, etc.) are extracted.
Remaining point features and the line features that cannot be extracted automatically (small paths, fences, etc.) are extracted
manually by the operators. Finally all data extracted automatically, semi-automatically and manually are combined and checked and
the photogrammetric production steps are completed. In the latter part of this paper, the problems faced and the subsequent solutions,
while applying the new alternative system, are introduced. Finally, both systems are compared to each other according to the
accuracy, production duration and cost.
1. INTRODUCTION
In recent years, technology has become cheaper and more
widespread and developed, and this has made it possible in
photogrammetry to reduce the map production costs. Using
digital cameras and GPS/IMU systems in taking aerial
photographs and in aerial triangulation, there is an opportunity
of reducing the number of ground control points that must be
established due to map production, film costs, photo-laboratory
costs and the scanning costs which are done at sensitive
scanners.
On the other hand, photogrammetric feature extraction is one of
the biggest components of the map production process in the
sense of time spent and costs. Minimizing this step and the
operator effects in map the production process affects the costs
directly in a positive way. That is why it is essential to integrate
automatic feature extraction developments into the map
production systems.
In the second part of this study, the methodology and
photogrammetric feature extraction steps applied in present
1:25.000 scaled map production process in General Command
of Mapping are investigated and the time spent and costs are
scrutinized.
In the third part of the study, a new alternative system is
proposed to reduce the production duration, operator effect and
the costs. By introducing the alternative system, it is aimed to
integrate a semi-automatic feature extraction software to the
map production process. In the final part of the study, the
problems faced when using the alternative system, and the
reasons for them, are taken up. Both systems are compared to
each other regarding the production duration and costs.
2. PRESENT WORKFLOW OF 1:25.000 SCALE
PHOTOGRAMMETRIC MAP PRODUCTION
In the present work of 1:25.000 scaled photogrammetric map
productions (revision of old maps), 1:35.000 scaled black and
white aerial photographs are used in General Command of
Mapping. The aerial photographs are digitized by scanning in
the precision of 20-21 microns. Aerial triangulation is carried
out by kinematic GPS and outer orientation parameters of each
photograph are determined by bundle block adjustment.
In the present work, all topographic features except contour
lines are extracted by the operators three dimensionally from the
stereo models which are created by using the outer orientation
parameters of each photograph.
Contour lines are imported from the DECM that is created for
the whole country once, and verified by overlapping on the
stereo models. The contour lines which are different and
incorrect according to the stereo model are corrected by editing
or deleting and reprocessing. Photogrammetric production is