1. ACCURACY OF PHOTOMOD AERIAL TRIANGULATION
Ivan KATZARSKY, Vanya PETROVA
GIS SOFIA Ltd., Bulgaria

2. INTRODUCTION
For evaluation the capacity of a digital photogrammetric system of special
importance is the accuracy of the aerial triangulation
An experiment in 4 variants in Photogrammetry Department at GIS
SOFIA Ltd. determines the accuracy of PHOTOMOD

3. TEST AREA SOFIA MUNICIPALITY Aerial photography
Test area characteristics
Area: hectares
Terrain: flat, lightly hilly and hilly not dense urban area with predominantly
low houses
Average height of the terrain above sea level: 750 m
Aerial photography
Contractor: Hansa Luftbild Sensorik und Photogrammetry GmbH, Münster
Execution of the photo-flight:
Aircraft: Cessna 404 Titan
Aerial camera: Zeiss RMK TOP 30/23 (Z/I Imaging)
Overlap between the pictures: forward 60 %, side 30 %
Aerial film: Kodak Aerocolor Negative 2444 III, 19 DIN
Film processor: Colenta

4. Scanning Land surveying DELTASCAN
GeoSystem Scientific Production Enterprise
12 μm pixel size
Land surveying
Pre-marked on the terrain ground control and
check points, determined by GPS-receiver
Topcon GGD with an accuracy of ± 2 cm
in position and ± 3 cm in height

5. EXPERIMENT DESCRIPTION
General information
Blocks of aerial pictures……………………………………………….. 1
Strips of aerial pictures………………………………………………… 6
Aerial pictures…………………………… = 105
Approximate picture scale…………………………………….. 1 : 4710
Average flight height above the terrain, m……………………… 1440
Ground pixel size, cm………………………………………………. 5.7
Pre-marked points on the terrain……………………………………. 36
Pictures per 1 pre-marked point……………………………………… 3
Tie points…………………………………………………………….. 786

6. Scheme of the experimental block

7. Experimented variants
Aerial triangulation by PHOTOMOD 4.2 modules
PHOTOMOD Montage Desktop
PHOTOMOD AT
PHOTOMOD Solver
Polynomial correction of 2nd degree in X, Y and Z axes are applied

8. Accuracy on the terrain, based on ground control points
RESULTS
The accuracy of aerial triangulation is evaluated by mean square
differences between geodetic and photogrammetric coordinates
of the ground control and check points
Accuracy on the terrain, based on ground control points

9. Accuracy on the terrain, based on check points

10. ANALYSIS
The mean square differences between geodetic and photogrammetric
co-ordinates of the ground control points are in the following range
In X-axis : ± 3.2 cm to ± 3.8 cm
In Y-axis : ± 1.1 cm to ± 3.7 cm
In XY-plane : ± 4.0 cm to ± 5.0 cm
In Z-axis : ± 2.3 cm to ± 7.1 cm
The mean square differences between geodetic and photogrammetric
co-ordinates of the check points are in the following range
In X-axis : ± 4.5 cm to ± 7.3 cm
In Y-axis: ± 4.3 cm to ± 9.3 cm
In XY-plane: ± 6.3 cm to ± 11.8 cm
In Z-axis: ± 8.0 cm to ± 26.7 cm

11. CONCLUSIONS
PHOTOMOD aerial triangulation, based on one ground control point
per 4 to 7 pictures, shows best result
The results strongly depend on the experimental conditions and
parameters. It gives an idea only for the capacity of PHOTOMOD
aerial triangulation. Another experiment could show other results
Aerial triangulation carried out by PHOTOMOD shows a reliable
accuracy

12. THANK YOU FOR YOUR ATTENTION!
Authors
Assoc. Prof. Dr. Ivan Katzarsky
22 Omourtag Street
BG-1124 Sofia, Bulgaria
Tel.: +359 (0)
GSM: +359 (0)
Vanya Petrova, M.Sc.
GIS SOFIA Ltd., Photogrammetry Dept.
5 Serdica Str., BG-1000 Sofia, Bulgaria
Tel.: +359 (0) ;
GSM: +359 (0)