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

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

TEST AREA SOFIA MUNICIPALITY Aerial photography Test area characteristics Area: 3103 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: 19.05.2006 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

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

EXPERIMENT DESCRIPTION General information Blocks of aerial pictures……………………………………………….. 1 Strips of aerial pictures………………………………………………… 6 Aerial pictures…………………………… 14+17+18+18+19+19 = 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

Scheme of the experimental block

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

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

Accuracy on the terrain, based on check points

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

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

THANK YOU FOR YOUR ATTENTION! Authors Assoc. Prof. Dr. Ivan Katzarsky 22 Omourtag Street BG-1124 Sofia, Bulgaria Tel.: +359 (0)2 8466953 GSM: +359 (0)88 5325509 ikatzarsky@abv.bg Vanya Petrova, M.Sc. GIS SOFIA Ltd., Photogrammetry Dept. 5 Serdica Str., BG-1000 Sofia, Bulgaria Tel.: +359 (0)2 9238338; 9307946 GSM: +359 (0)88 6067306 vpetrova@hotmail.com