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XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
Hannover
Section 5
Orthoimage generation
Emmanuel Baltsavias
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
Hannover
Orthoimage Generation
Older sensor models methods:
• Kratky’s Polynomial Mapping Functions (PMFs)
• Relief corrected affine transformation
- Project GCPs on reference plane (X, Y coordinate corrections) using sensorelevation and azimuth
- Reference plane -> reference plane of DTM
- Compute affine transformation between X, Y object and x, y pixel coordinates
- 3 GCP’s are needed but 4-6 are suggested
Current method:
• Use RPCs and subsequent shifts or affine transformation
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
Hannover
Orthoimage Generation
Test resultsLuzern
Method: Relief corrected affine transformation
Sens elev. (deg) 67.7DTM spacing/accur (m) 25 / 2.5 lowland, 10 AlpsGCP accuracy (m) 0.5 – 3GCP definition Very poor to goodElevation range (m) 400-2100
Version GCPs/CPs RMS/X RMS/Y Max. abs X Max. abs Y1 0 /66 134.2 30.6 501.5 118.12 6 / 65 2.6 2.2 9.9 5.95 6/14 0.6 0.6 1 1.1
CPs = check points
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
Hannover
Orthoimage Generation Test results
Method: Relief corrected affine transformation
Nisyros
Version GCP's/CPs RMS/X RMS/Y Max. abs X Max. abs Y1 0 / 38 106.1 75.5 153.1 122.82 4/34 1.7 1 4.4 2.33 4/15 0.9 0.6 1.5 1.4
Sens elev. (deg) 73.5DTM spacing/accur (m) 2 / 3.3 GCP accuracy (m) ca. 0.5GCP definition Poor to goodElevation range (m) 0-700
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
Hannover
Orthoimage generation (IKONOS, Quickbird) in Geneva
Input data
2 IKONOS Geo images (IKONOS-West / IKONOS-East)1 Basic QUICKBIRD Image
Orthoimages (for acquisition of GCPs):OP-DIAE: Digital Orthos of Canton Geneva (25 cm pixel size, 0.5 m planimetric RMS)Swissimage: Digital Orthos of Switzerland of Swisstopo (50 cm pixel size, 1m planimetric RMS)
DTMs:DTM-AV (from airborne laser scanning): 1 m grid spacing, 0.5 m height RMSDHM25 of Swisstopo (from digitised contours): 25 m grid spacing, 1.5-2 m height RMS
Measurement of GCPs with ellipse fit and line intersection.
Image orientation with various sensor models. RPCs with subsequent affine transformation used fororthoimage generation.
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
Hannover
GCP example: roundabout (Melbourne testfield)
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
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Roundabout measurement via ellipse fit
Edge points digitized semi-automatically, followed by ellipse fit
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
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Roundabout measurements via least-squares template matching
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
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User-interface for GCP measurement & block adjustment (Sat-PP ETHZ)
Ellipse Fitting
Sensor Modeling and Block Adjustment
Ellipse fitting mode
Line intersection mode
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
Hannover
Orthoimage generation (IKONOS, Quickbird) in Geneva
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
Hannover
Orthoimage generation (IKONOS, Quickbird) in Geneva
Pansharpened orthoimages. Left Ikonos, right Quickbird.
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
Hannover
Orthoimage generation (IKONOS, Quickbird) in Geneva
Definition of lines and circles. Left Ikonos, right Quickbird.
Note the large visual difference although pixel size is 1m and 0.7m respectively.
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
Hannover
Orthoimage generation (IKONOS, Quickbird) in Geneva
-0.38-0.080.600.5610/53Quickbird
-0.590.100.760.4710/33Ikonos East
-0.490.250.630.5510/23Ikonos West
Y meanwith sign (m)
X mean withsign (m)
Y RMS (m)X RMS (m)Number of GCPs/CPs
Image
Planimetric accuracy of panchromatic orthos with GCPs from OP-DIAE
(CPs = check points)
Quickbird is not more accurate than Ikonos although GSD was 0.7m and 1m respectively.
Planimetric accuracy could be even higher with well defined GCPs measured with GPS.
In Y mean (bias) large due to coordinate system differences (Geneva and national systems differ).
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
Hannover
Orthoimage generation (IKONOS, Quickbird) in Geneva
-0.11-0.060.770.6610/93Quickbird
-0.330.000.750.6710/57IkonosEast
-0.30-0.070.720.9110/58Ikonos West
Y meanwith sign (m)
X mean withsign (m)
Y RMS (m)X RMS (m) Number of GCPs/CPs
Image
Planimetric accuracy of panchromatic orthos with GCPs from OP-DIAE and Swissimage
Submeter accuracy even with GCPs from not so accurate Swissimage orthos.
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
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In-depth investigations of parameters influencing the accuracy of orthoimages from high resolution satellites
AIMS
The aim of this work was the analysis of orthoimage accuracy produced from IKONOS and QB images using different type of original data in Switzerland. More specifically, we were interested to see the influence on the planimetric accuracy of
- different sources for the measurement of GCPs (Ground Control Points),
- different elevation models and
- different sensor elevation.
The whole processing was performed mainly with Sat-PP (Satellite Imagery Precision Processing) software developed at IGP which makes use of good quality algorithms, especially for DSM generation and semi-automatic point measurement and feature extraction. The software can be used with any type of imagery, digital and scanned film, frame and linear sensors.
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
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Specifications of the data
The first area, Thun, lies in the central part of Switzerland 40 km southern of the capital of Switzerland, Bern. In this region in 2004, we established a testfield with a coverage of 15 by 20 sqkm for the analysis of high resolution satellite images.
Later in 2006, this testfield was extended for the analysis of ALOS images to the neighborhood of Bern and Thun (30 by 30 sqkm). In the area of Geneva we used two IKONOS and one QB images. The test area had a size of 16 by 17 km.
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
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Specifications of used satellite images:
82.1372.206Reverse2003-12-25Thun_I_163003_100
62.95180.39Reverse2003-12-25Thun_I_163003_000
61.6240.2Reverse2001-05-28Geneva_I_East
67.2253.6Forward2001-05-28Geneva_I_West
77.6286.4Reverse2003-07-29Geneva_Q
Sensor-Elevation (deg)Sensor- Azimuth (deg)Scanning modeDate of acquisitionImage
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
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Resolution and accuracy of used orthoimages and DTMs:
average deviation to DHM25 is about 17
Flat-hilly-Jura: 1.5
Voralps: 2Alps: 5 - 8
0.5/vegetation
:1.5
0.50Accuracy of the height [m]
1.00.50Planimetric accuracy [m]
25025.02.00.501.00.25GSD / grid spacing [m]
DHM25DTM-AVUsed elevation model
LV03LV03LV03LV03LV03-GELV03-GEReference frame
Swiss Federal Office of Topography (Swisstopo)Canton GenevaProduced by
RiminiDHM25 DTM-AVSwissimageDTM-AV OP-DIAE
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
Hannover
RESULTS
Orthoimage accuracy in the Geneva test area:
CPs = check points
Max AbsoluteRMSEMeanNumberof CPs
2.81.11.00.7-0.20.213QB_DHM25
2.61.20.90.6-0.20.213QB_DTM-AV
2.51.71.20.8-0.70.011IKONOS_East_DHM25
2.00.71.10.3-0.70.211IKONOS_East_ DTM-AV
1.81.91.11.00.0-0.49IKONOS_West_DHM25
1.90.81.00.50.00.110IKONOS_West_ DTM-AV
Y (m)X (m)Y (m)X (m)Y (m)X (m)Orthoimage version
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
Hannover
Results from the image orientation in Thun:
GCP = Ground Control Points
0.980.900.7478Orthoimage/DHM252003-10-12
0.690.660.7068DGPS2003-10-12
1.360.600.6048Orthoimage/DHM252003-12-25
0.560.400.37278DGPS2003-12-25
z-RMS [m]y-RMS [m]x-RMS [m]CPGCPType of GCPDate ofImage
Acquisition
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
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Orthoimage accuracy in the Thun test area:
83ORTHO
83GPS
63ORTHO
63GPS
83ORTHO
83GPS
63ORTHO
63GPS
83ORTHO
83GPS
63ORTHO
63GPS
83ORTHO
83GPS
63ORTHO
63GPS
Type of GCPSensor
elevation Y (m)Y (m)Y (m) X (m)X (m)X (m)Elevation model
Max AbsoluteRMSEMeanNumberof CPs
Orthoimage version
2.43.21.01.10.4-0.310LIDAR
2.12.41.20.8-0.90.311LIDAR
2.82.91.21.20.3-0.611LIDAR
2.02.61.01.0-0.2-0.412LIDAR
2.31.91.00.7-0.40.119Matching
1.91.71.00.7-0.70.217Matching
2.94.01.11.3-0.40.120Matching
3.53.21.21.1-0.50.220Matching
2.61.91.20.8-0.80.119DHM25
3.22.21.30.9-0.90.217DHM25
10.22.43.71.0-0.3-0.120DHM25
9.63.73.61.0-0.40.120DHM25
4.53.52.01.2-0.70.321Rimini
3.62.32.01.0-1.20.421 Rimini
22.95.78.81.7-0.90.120Rimini
22.43.08.01.2-0.90.020Rimini
XXIst ISPRS Congress, Beijing, China, Tutorial-10, July 3rd, 2008
Leibniz
Universität
Hannover
Conclusions
High accuracy DTM/DSM, as the DTM/LIDAR and the matching DSM, provide more similar accuracy in X and Y, quite independently of the sensor azimuth and elevation.
As the DTM/DSM accuracy deteriorates, a higher sensor elevation is needed and the height errors are distributed in X and Y differently, depending on sensor azimuth.
For high sensor elevation (in this case 83 degrees), an orthoimage accuracy of 1-2.5 m was achieved even with the RIMINI dataset.
The major influence on the orthoimage accuracy is from the DTM/DSM and the sensor elevation.
The role of GCP accuracy, as long as this is within certain limits (e.g. at least one GSD) is subordinate. Since GCP acquisition is costly and time consuming, the selection of GCP acquisition method should be made based on the accuracy of the available DTM/DSM and the sensor elevation.
Orthoimages with submeter accuracy can be produced even with suboptimal DSMs / DTMs and GCPs. Accuracy can reach 0.5 GSD.