test ranges for metric calibration and validation of satellite imaging systems gene dial...
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Test Ranges for Metric Calibration and Validation of Satellite Imaging Systems
Gene Dial ([email protected])Jacek Grodecki ([email protected])
© 2003 Space Imaging, LLC. Confidential and proprietary.
TopicsIKONOS IntroductionImportance of Clear SkiesPreflight test ranges
Requirements ValidationPost Launch Test Ranges
Recalibration Accuracy Test & Monitoring
Ground Control Points Good & Bad Image Display Effects High Quality
Summary & Conclusions
© 2003 Space Imaging, LLC. Confidential and proprietary.
IKONOS SatelliteIKONOS Satellite
Use• Simultaneous Pan and Multispectral images
• Panchromatic pixels: 0.82 m at nadir
• Multispectral pixels: 3.28 m at nadir(Blue, Green, Red, NIR)
• Linear detector arrays scan in any direction
• Swath width: 10.8 km at nadir
Image Specifications
Use• 680-km near-polar, sun-synchronous orbit.
• 3-day revist with elevation > 60°
• 25 m CE90 accuracy without GCP
• 2 m CE90 accuracy with GCP
• Same pass stereo strips up to 400 km long
•25 m CE90 horizontal, accuracy
•22 m LE90 vertical accuracy
Metric Specifications
© 2003 Space Imaging, LLC. Confidential and proprietary.
Ceduna
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pro
bab
ility
0
<5
<10
<50
Alice Springs
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pro
bab
ility
0
<5
<10
<50
Select Low-Cloud Areas for Test Ranges
Gene Dial, SIE, 4/5/97
Townsville020406080100123456789101112MonthProbability 0<5<10<50
Tidbinbill020406080100123456789101112MonthProbability 0<5<10<50
Hobart020406080100123456789101112MonthProbability 0<5<10<50
Alice Springs020406080100123456789101112MonthProbability 0<5<10<50
Ceduna020406080100123456789101112MonthProbability 0<5<10<50
Darwin020406080100123456789101112MonthProbability 0<5<10<50
Karratha020406080100123456789101112MonthProbability 0<5<10<50
Dongara020406080100123456789101112MonthProbability 0<5<10<50
Hobart
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pro
bab
ility
0
<5
<10
<50
Darwin
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pro
bab
ility
0
<5
<10
<50
Karratha
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pro
bab
ility
0
<5
<10
<50
Dongara
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pro
bab
ility
0
<5
<10
<50
Townsville
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pro
bab
ility
0
<5
<10
<50
Tidbinbill
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pro
bab
ility
0
<5
<10
<50
© 2003 Space Imaging, LLC. Confidential and proprietary.
Northern Test RangePurpose: Verify RequirementsSize: 20 km NS x 30 km EWGCP: 140 cultural featuresAccuracy: 0.5 m CE90, 0.9 m LE90Source: Large-scale aerial photographyImagery: “San Diego Seven”
Stereo triplet on the West Stereo pairs center and East Supplied to SW developers for test
Results: IKONOS meets requirements. Without Ground Control
– 25 m CE90 horizontal – 22 m LE90 vertical
With Ground Control– 2 m CE90 horizontal– 3 m LE90 vertical
© 2003 Space Imaging, LLC. Confidential and proprietary.
Southern Test Range
200 GCP in 100 km x 100 km areaDifferential GPS SurveyNS line for exterior orientationEW line for interior orientationMany points difficult to identify
Chip at lower right shows 1 m by 2 m black rectangle on 1 m diameter white water pipe
© 2003 Space Imaging, LLC. Confidential and proprietary.
Interior & Exterior Orientation
X
Z Y
2-D ImageSpace
PerspectiveCenter
3-D GroundSpace
Interior Orientation- Optics- Mechanical alignments- Relates field angles toimage detectors
Exterior Orientation- Position (Ephemeris)- Attitude (Angles)- Relates 3-D groundpositions to field angles
RPCComplete3-D Objectto 2-DImageRelation-ship
© 2003 Space Imaging, LLC. Confidential and proprietary.
Case Study: 6 Stereo Pair, 60 GCP
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2000050818200180000010117938200005081821035000001011794020000621182509500000116123512000062118260060 00001161235220010314182726600000101289512001031418274050000010128949200103141828168000001012895220010314182829900000101289502001032518284320000010105273200103251829016000001010527520010325182931900000101052742001032518295100000010105276 5 0 5 10 Miles
N
EW
S
Processed with one GCP.Remaining GCP test accuracy.
© 2003 Space Imaging, LLC. Confidential and proprietary.
Original Field Angle Map, 1 GCP
Latitude Longitude Height Str. Line (meters) (meters) (meters) (meters) Mean 0.45 1.66 0.74 4.98 Std. Dev.(68) 0.79 5.51 1.65 2.95 Std. Dev.(90) 1.3 9.06 2.71 4.85 Maximum 1.98 11.86 4.57 11.86 Minimum -1.33 -6.71 -2.47 0.2Points: 60
CE90 = 8.6 m
Project Area 6 Stereo Pair Wide Precision GCP
Residual Error Pattern All residuals point to GCP Suggestive of scale error About 2 m per strip
Corrective Action Denver test range for
FAM calibration Interior orientation
adjusted Scale Error Removed
© 2003 Space Imaging, LLC. Confidential and proprietary.
Calibration of Interior Orientation
Residual - Line
-2.0-1.00.01.02.0
-80.0-60.0-40.0-20.00.020.040.060.080.0
West - East
Residual - Sam ple
-2.0-1.00.01.02.0
-80.0-60.0-40.0-20.00.020.040.060.080.0
West - East
© 2003 Space Imaging, LLC. Confidential and proprietary.
After FAM Recalibration of Nov 19, 2001.
Latitude Longitude Height Str. Line (meters) (meters) (meters) (meters) Mean 0.61 -0.02 -0.06 1.13 Std. Dev.(68) 0.67 0.86 1.62 0.51 Std. Dev.(90) 1.1 1.41 2.66 0.83 Maximum 2.24 1.92 3.38 2.72 Minimum -1.29 -1.85 -3.78 0.23Points: 60
CE90 = 1.8 m
© 2003 Space Imaging, LLC. Confidential and proprietary.
Exterior OrientationRepeated acquisitions of MTF target
Target surveyed by differential GPS
Median error measured
Interlock angles adjusted to zero median error.
Pitch Interlock, uR
-20.0
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
20.0
12/1/1999 3/30/2000 7/28/2000 11/25/2000 3/25/2001 7/23/2001 11/20/2001
Fwd Pitch
Rev.Pitch
Initialization
Roll Interlock, uR
-20.0
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
20.0
12/1/1999 3/30/2000 7/28/2000 11/25/2000 3/25/2001 7/23/2001 11/20/2001
Fwd Roll
Rev.Roll
Initialization
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Repeated Acquisitions to Verify Interlock Angles
Position Error, East
-10
-5
0
5
10
5/1/2000 5/1/2001 5/1/2002 5/1/2003
Eas
ting
(m)
Target 18
Target 19
Target 21
Target 22
Position Error, North
-10
-5
0
5
10
5/1/2000 5/1/2001 5/1/2002 5/1/2003
No
rth
ing
(m
)
Target 18
Target 19
Target 21
Target 22
© 2003 Space Imaging, LLC. Confidential and proprietary.
Ad-hoc Tests of System AccuracyProcedure
Acquire GCP for Precision orders Process Imagery without GCP Evaluate Errors
Example 49 check points 24 stereo pairs
Reference: Dial, IKONOS Stereo Accuracy, ASPRS 2003.Stereo Position Errors
10 m
15 m
25 m
East
North
GCP: Cultural Features Range-only differential 1 m CE90, 2 m LE90.
Result: IKONOS Stereo Accuracy 6 m CE90 Horizontal 10 m LE90 Vertical
© 2003 Space Imaging, LLC. Confidential and proprietary.
RepeatabilityTrial X Y
1 4.563 5.81252 4.313 5.81253 4.688 5.56254 4.563 5.43755 4.688 5.5625
Max 4.688 5.813Min 4.313 5.438Range 0.375 0.375Median 4.563 5.563Average 4.563 5.638Std Dev 0.153 0.168
Results of 5 trials with 1 operator Range = 0.375 pix Sigma = 0.16 pix
Operator variation could be significant
© 2003 Space Imaging, LLC. Confidential and proprietary.
Effect of Resampling and Contrast on Corner Position
Change from NN to CC resampling moves apparent corner position by 0.25 pixels
© 2003 Space Imaging, LLC. Confidential and proprietary.
Contrast: Low vs. High
© 2003 Space Imaging, LLC. Confidential and proprietary.
Brightness: Light & Dark
© 2003 Space Imaging, LLC. Confidential and proprietary.
Effect of Resampling, Brightness, & Contrast
Resampling effect is in the noise level. Contrast changes had no effect on perceived position.Brightness changes had a significant effect
Bright images – Lower contrast to white square– Increase contrast to black square– Operator picks further away from black corner
Dark images have converse effectsIdeal GCP are centerline, not corner features.
Case X Y dX dYNearest Neighbor 4.563 5.4375 -0.0625 -0.1250Cubic Convolution 4.563 5.6875 -0.0625 0.1250
Low Contrast 4.813 5.5625 0.1875 0.0000High Contrast 4.688 5.5625 0.0625 0.0000
Bright 5.063 5.1875 0.4375 -0.3750Dark 4.438 5.8125 -0.1875 0.2500
© 2003 Space Imaging, LLC. Confidential and proprietary.
Examples of Good Ground Control
Good Ground Control Points Intersection of Cross-Walk and Stop Lines Sidewalk intersection Home plate at baseball field Intersection of Service Line and Center Line of a Tennis Court
– Intersection of Side Lines with Base Line is not good.
© 2003 Space Imaging, LLC. Confidential and proprietary.
Examples of Poor Ground Control
Examples of Poor GCP Locations Dirt Road Intersection Acute road intersection Walled compounds
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GCP Panels for IKONOSGCP Panels for IKONOS
“Tyvek” panels Aligned North-South. Control point is center square
Lessons Learned Tests with 3 observers agreed
within 0.05 m RMS. Narrow gap sometimes hard to see End panels unnecessarily large
– Hard to deploy– Too bright
See revised design at right
References Dennis Helder, Michael Coan, &
Peter Gaska, “IKONOS Geometric Characterization” RSE 2003.
Michael Coan, telecon & email.
Original
Revised1.5'
6'
6'
3' x3'
1.5'
4.5'
4.5'
© 2003 Space Imaging, LLC. Confidential and proprietary.
Multi-Point Measurements Reduce GCP Pick ErrorMultiple Point Measurements
Average errors of individual points. Symmetric distribution eliminates bias
at contrast edge. Accuracy ~ 0.2 pixels
Reference C.S.Fraser, H.B.Hanley & T.Yamakawa,
“Sub-metre Geopositioning with IKONOS Geo Imagery, ISPRS Joint Workshop “High Resolution Mapping from Space 2001”, Hanover, Germany 19-21 September
© 2003 Space Imaging, LLC. Confidential and proprietary.
Summary & ConclusionsMetric Test Range Applications
Requirements Verification Calibration of Interior & Exterior Orientation Verification of System Accuracy Monitoring of System Accuracy
Test Range Considerations High probability of cloud-free skies Availability of geodetic control Overall size suitable for sensor Cultural features suitable for ground control
Ground Control Points Use centerline, not corner features For ultimate accuracy
– Deploy panels or use multi-point measurementsThank you.