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Testing data from the GeoEye-1 satellite in PHOTOMOD digital photogrammetric workstation

A.E. Zubarev, Racurs, Moscow, Russia

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Experts from Racurs Company have conducted a test of data from the GeoEye-1 satellite with PHOTOMOD digital photogrammetric workstation version 4.4.699. A stereopair of space images (PAN and RGB) for the area of Hobart city (Tasmania, Australia) shot Feb 17, 2009 was processed.

Product Type: GeoStereo
Level of processing: Standard Geometrically Corrected
Type of image: RGB
Format: GeoTIFF
Radiometric resolution: 8 bits
Resolution: 0,5 meters
Type locality: Middle mountains
Elevation difference: 1260 meters


These images are the result of the synthesis (pan-sharpening) of basic pairs of PAN images (resolution: 0.5 m ) and BGRN (resolution: 2,0 m) in PHOTOMOD digital photogrammetric workstation version 4.4.

1. GCPs identification accuracy on images


In this example, GCP was assigned to the center of the circumference

2. GCPs transfer accuracy on the neighbor image


As it can be seen from the figure above, the maximum parallax is - 0.2526 and RMS - 0.1220 (values are given in pixels).

3. The arrangement of GCPs and check points


10 check points and 3 GCPs have been measured on the stereopair.

4. Method of adjustment: RPC

4.1. Results of the adjustment (without GCPs, by metadata only).

Accuracy:

Type of residuals Estimate of residuals (meters)
Ex Ey Ez
Check points
RMS 3.08 0.54 9.85
Mean residuals 3.07 0.53 9.84
Max 3.30 0.66 10.90

4.2. Results of the adjustment (1 GCP, 12 check points)

Accuracy:

Tape of residuals Estimate of residuals (meters)
Ex Ey Ez
GCPs
RMS 0 0 0
Mean residuals 0 0 0
Max 0 0 0
Check points
RMS 0.161 0.161 0.645
Mean residuals 0.130 0.136 0.482
Max 0.364 0.268 1.380

4.3. Results of the adjustment (10 GCP, 3 check points)

Accuracy:

Tape of residuals Estimate of residuals (meters)
Ex Ey Ez
GCPs
RMS 0.105 0.051 0.186
Mean residuals 0.094 0.047 0.133
Max 0.145 0.075 0.472
Check points
RMS 0.046 0.033 0.298
Mean residuals 0.042 0.023 0.290
Max 0.069 0.056 0.382

5. Creation of digital terrain model (DTM)

Creation of DTM from the stereopair of space images was carried out in PHOTOMOD 4.4 by automatic calculation of pickets on a regular grid. Then breaklines were drawn manually along the main thalweg and ridges in 1:2 zoom. A TIN was built from these vectors and pickets, with subsequent semi-automatic filtration of edges. Contour lines were created for additional control, and quality of TIN creation and filtering was evaluated visually. A DEM was created within the area of the stereopair after the final correction. Preliminary accuracy of created DEM is appr. 2 m. The resulting DEM is shown below.

6. Construction of ortophoto

Primary control of the future ortophoto was performed in PHOTOMOD Mosaic 4.4. Control was carried out on the check points available in the project. The resulting table is shown below.
Quantity of images in the mosaics: 2
Pixel size: 0.5 m
Table of difference between DEM and GCPs

Name of point XY plane residuals
(meters)
B1_01 1,685
B1_05_A 0,000
B1_10 1,220
B2_01 0,437
B3_09 0,204
B3_10 0,866
B4_02 0,222
B5_03 0,854
B6_07 0,149
B7_10 1,490
B9_11 0,142
B9_15 0,399
B8_04_A 0,096

Table of estimate difference between DEM and GCPs
Tape of estimate XY plane residuals
(meters)
RMS 0,809
Mean residuals 0,597
Max 1,685

From the given tables one can conclude that this data is suitable for creation of orthopho of 1:5000 scale

Fragments of the created orthophoto are shown below. These fragments are given in 1:1 zoom.

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Last modified: 06.12.2018© Racurs, 2004-2018