Test Ranges for Metric Calibration and Validation of Satellite Imaging Systems Gene Dial...

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


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


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


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


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


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


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.


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


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


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


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


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


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


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


Effect of Resampling and Contrast on Corner Position

Change from NN to CC resampling moves apparent corner position by 0.25 pixels


Contrast: Low vs. High


Brightness: Light & Dark


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


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.


Examples of Poor Ground Control

Examples of Poor GCP Locations Dirt Road Intersection Acute road intersection Walled compounds


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'


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


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.

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Test Ranges for Metric Calibration and Validation of Satellite Imaging Systems Gene Dial...

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