1 (edited by James_Hollingsworth 2010-07-13 15:53:17)

Topic: KH9 Hexagon satellite images

KH9 Hexagon satellite images are essentially very very high altitude aerial photos, since they are acquired with a frame camera system.

Here's how to get started orthorectifying them. I've correlated them with SPOT5 satellite imagery (aqcuired with the completely different pushbroom system) and had great success! Processing Hexagon images is not difficult, but certainly more time consuming than Landsat, ASTER and SPOT. Here's a quick summary:

1. You can buy your Hexagon images from the USGS for $30 a pop.

2. When they arrive, you need to stitch the two halves of the Hexagon image together. You will notice there are crosses (reseau points) on the Hexagon images... there are 23 in the x-direction and 47 in the y-direction. If the very center reseau point has a coordinate of (0,0), and x increases to the right, and y increases up the image, then the reseau point with the coordinate (23,23) should have a little flag on it. This should be visible on both halves of the raw Hexagon image, and which you can use to mosaic the two images together using the Mosaicing > Pixel-based tool in ENVI. Once your two image halves are adequately mosaiced together, rotate the image so North is at the top. (* it is best if the feature of interest is far away from the stitching line i.e. in the middle of either of the two halves is ideal).

3. To generate the interior orientation info, I use the reseau-based coordinate system described above. The distance between each reseau point is 1 cm, and so the Upper Left fiducial would be x = -110 mm y = 230 mm, Upper Right: x = 110 mm, y = 230 mm, Lower Right: x = 110 mm, y = -230 mm, Lower Left: x = -110 mm, y = -230 mm. For the focal length, use 30.5 cm. Don't worry about optical distortions for the moment, since we don't actually know what they are. If the magnitude of displacements you are measuring is greater than 10 m then the errors introduced by optical and film distortions will be relatively small. Otherwise, I've managed to image 4 m fault displacements, but this only works because the signal is high-frequency. Distributed deformation of 10 m or less will be very difficult to see above the noise.

4. The rest of the procedure is relatively painless... you use the aerial photo module in Cosi-Corr, and process the hexagon image as if it were an aerial photo. I usually orthorectify them at 7 m resolution.

2

Re: KH9 Hexagon satellite images

I am trying to orthorectify KH9 Hexagon satellite images using COSI-Corr software by following your step.
Firstly, I mosaic the two images halves of the Hexagon image together.
Secondly, generate the interior orientation info as :
Upper Left fiducial  x = -110 mm y = 230 mm,
Upper Right: x = 110 mm, y = 230 mm,
Lower Right: x = 110 mm, y = -230 mm,
Lower Left: x = -110 mm, y = -230 mm.
3. selected the GCPs points from panchromatic band of Landsat 8 and ASTER GDEM V2.
4. successfully, generated the IO.
However, when I try to do the next step which is generate the EO, Error
was happen.
"EXTERIOR_ORIENTATION_CORE: Error in computing altitude(alt. null)"
Would you can help me solve this problem!

;Interior orientation file generated the :Wed Dec 09 17:27:04 2015
;Camera Calibration Report Available :
yes

;Focal of the camera (in meters)
3.0500000000000

;Principal Point location in millimeter (x, y):
0.0000000000000     0.0000000000000

;Fiducial Points
;Fiducial (x,y) (millimeter), Image (x,y)(pixel)
;Note 1: If Camera Calibration not available, fiducial (x,y) are not used
;Note 2: The affine transformations (camera-to-image and image-to-camera)
;are computed assuming a positive counterclockwise image reference system.
;If the image reference system is not positive counterclockwise then the
;fiducial points measurements are converted on-the-fly before computation,
;by inverting x and y (x(mm)=y(mm) and y(mm)=x(mm)). The affine transformation
;coefficients below are expressed in a positive counterclockwise image
;reference system.
-110.0000000000000  -230.0000000000000  1066.5000000000000 33424.5000000000000
110.0000000000000   230.0000000000000 67014.0000000000000  1986.0000000000000
110.0000000000000  -230.0000000000000 66991.0000000000000 33520.0000000000000
-110.0000000000000   230.0000000000000  1086.0000000000000  1891.2500000000000

;Coefficients for affine transformation
;from Camera to Image
;x(pix) = a0 + a1*x(mm) + a2*y(mm)
;y(pix) = b0 + b1*x(mm) + b2*y(mm)
34039.3750000000000
299.6647727272728
0.0461956521739
17705.4375000000000
0.4323863636364
-68.5513586956522

;Coefficients for affine transformation
;from Image to Camera
;x(mm) = a0 + a1*x(pix) + a2*y(pix)
;y(mm) = b0 + b1*x(pix) + b2*y(pix)
-113.6312185654076
0.0033370590005
0.0000022487923
257.5631650369564
0.0000210484326
-0.0145875887296

;Distortions measured with radial distance
;- yes : radial distance in millimeters
;- no : field angle in decimal degree
yes

;Radial distortion values
0.0000000000000     0.0000000000000

;Radial distortion coefficients - lenses correction
0.0000000000000     0.0000000000000     0.0000000000000

;Tangential distortion coefficients - lenses correction
0.0000000000000     0.0000000000000     0.0000000000000

;Atmospheric distortion correction
yes


;File generated the : Wed Dec 09 16:39:15 2015
;GCPS generated from :
;- Tied point file : H:\m_paper\declassified\corr-cosi\tie_p.pts
;- GeoReferenced image : H:\new_invontory\2014\landast\LC81480352014166LGN00_B8.TIF
;- DEM : C:\Users\haireti\Desktop\ASTGTM2_N35E076\dem_15s.tif
;Geographic coordinates of the GCPS with respect to the datum of the Georeferenced image
;Values : Easting, Northing, Altitude, X, Y, Weight, Opti, dE, dN, dA
;Note : Opti, dE, dN, and dA, are only used in GCPS Optimization
76.1538734701     35.6735985774    3595.4780   43276   23387   1.00000   1     0.0000     0.0000     0.0000
76.3333823614     36.0315937187    4361.6085   32373   21031   1.00000   1     0.0000     0.0000     0.0000
76.4107303208     36.0838520496    3864.1072   30547   19519   1.00000   1     0.0000     0.0000     0.0000
76.3726151749     36.0091090399    4029.3507   32845   20003   1.00000   1     0.0000     0.0000     0.0000
76.7315620102     35.8546380510    4609.7486   35757   10870   1.00000   1     0.0000     0.0000     0.0000
76.1828466126     36.0404757277    4573.0913   32725   24573   1.00000   1     0.0000     0.0000     0.0000
76.8414963230     35.7889082383    4543.9427   37164    7982   1.00000   1     0.0000     0.0000     0.0000
77.0054824564     35.7235429105    4972.0701   38348    3776   1.00000   1     0.0000     0.0000     0.0000

Thank you very much for your help

3

Re: KH9 Hexagon satellite images

Dear Haireti,

Hexagon Camera Calibration report is not publicly available. That means that you need to setup your IO using the "no calibration report" option (at the top of the IO GUI). You'll need to provide the focal length, the scan resolution (see provider of scanned image), and the fiducial points coordinates (only the pixel coordinates are of importance, coordinates in mm are not used as you don't have them (no report)).

Best,
Francois

4

Re: KH9 Hexagon satellite images

Hi! Francois
After your correction, It was working. However, I just used 10 GCPs which resulted final result was shifting more than expectation.
Therefore, I think more GCPs were needed.
Thank you for your help!
Haireti

5

Re: KH9 Hexagon satellite images

Hi!
Recently, I am trying to orthorectify another KH9 Hexagon satellite images using COSI-Corr software by following your step.
1.    mosaicking
2.    Interior orientation (selecting  fiducial point and selected the GCPs points from panchromatic band of Landsat and ASTER GDEM V2)
3.    Generate Io
4.    Selecting tie points and converted to the GCPS
5.    GCPs optimization
But, I got the error message in `GCPs optimization’ [Exterior orientation core: error in computing altitude (alt.null)]. I checked the DEM, and other files, but, I cannot solve the problem.
It would be nice you can help me solve this problem!   

This generated IO:
;Interior orientation file generated the :Thu Apr 27 11:23:50 2017
;Camera Calibration Report Available :
no

;Focal of the camera (in meters)
0.3050000000000

;Scan Resolution in millimeter (x, y):
0.0070000000000     0.0070000000000

;Fiducial Points
;Fiducial (x,y) (millimeter), Image (x,y)(pixel)
;Note 1: If Camera Calibration not available, fiducial (x,y) are not used
;Note 2: The affine transformations (camera-to-image and image-to-camera)
;are computed assuming a positive counterclockwise image reference system.
;If the image reference system is not positive counterclockwise then the
;fiducial points measurements are converted on-the-fly before computation,
;by inverting x and y (x(mm)=y(mm) and y(mm)=x(mm)). The affine transformation
;coefficients below are expressed in a positive counterclockwise image
;reference system.
110.0000000000000   230.0000000000000 33704.7500000000000  1055.0000000000000
110.0000000000000  -230.0000000000000 33620.0000000000000 67325.5000000000000
-110.0000000000000  -230.0000000000000  1939.7500000000000 67269.0000000000000
-110.0000000000000   230.0000000000000  2009.7500000000000  1058.0000000000000

;Coefficients for affine transformation
;from Camera to Image
;x(pix) = a0 + a1*x(mm) + a2*y(mm)
;y(pix) = b0 + b1*x(mm) + b2*y(mm)
17818.5625000000000
142.8571428571429
0.0000000000000
34176.8750000000000
0.0000000000000
142.8571428571429

;Coefficients for affine transformation
;from Image to Camera
;x(mm) = a0 + a1*x(pix) + a2*y(pix)
;y(mm) = b0 + b1*x(pix) + b2*y(pix)
-124.7299375000000
0.0070000000000
0.0000000000000
-239.2381250000000
0.0000000000000
0.0070000000000
;Distortions measured with radial distance
;- yes : radial distance in millimeters
;- no : field angle in decimal degree
yes
;Radial distortion values
0.0000000000000     0.0000000000000
;Radial distortion coefficients - lenses correction
0.0000000000000     0.0000000000000     0.0000000000000
;Tangential distortion coefficients - lenses correction
0.0000000000000     0.0000000000000     0.0000000000000
;Atmospheric distortion correction
yes
And tie points and converted GCPS

; ENVI Image to Image GCP File
; base file: F:\new_invontory\2000\landasat\LE71480352000168SGS01_B8.TIF
; warp file: F:\m_paper\declassified\2002\DZB1216-500361L006001\today\mosaic_envi_r
; Base Image (x,y), Warp Image (x,y)
;
      11566.000000      10165.000000      21174.250000      19738.500000
       7958.000000       8447.000000       6073.250000      15230.500000
       7572.000000       6952.000000       3774.500000       9768.250000
       7678.000000       4752.000000       3015.750000       1390.500000
      13998.000000       5888.000000      28101.000000       1870.000000
      11605.000000      13790.000000      23439.000000      33941.000000
       7859.000000      12596.000000       8165.750000      31474.000000
      10486.000000       5355.000000      14147.750000       1799.500000
      10185.000000       6376.000000      13540.750000       5784.000000
      13729.000000       7226.000000      27881.750000       7095.000000
      10101.000000       8210.000000      14282.500000      12979.000000
      13503.000000       8697.000000      27877.000000      12920.750000
       9911.000000      11126.000000      15242.750000      24481.250000
      10148.000000       9461.000000      15184.250000      17764.500000
      12845.000000      10787.000000      26561.250000      21422.500000
      12616.000000       5671.000000      22616.000000       1804.250000
      11514.750000       7233.250000      19246.500000       8392.750000
       7059.000000       9531.000000       3184.250000      19963.000000
      11082.000000      12721.000000      20768.250000      30047.250000
      12702.000000      12042.000000      26759.250000      26408.000000
       8906.000000      12813.000000      12306.000000      31695.250000
       8401.000000       5171.000000       6011.750000       2519.750000

;File generated the : Thu Apr 27 11:31:21 2017
;GCPS generated from :
;- Tied point file : F:\m_paper\declassified\2002\DZB1216-500361L006001\today\tie_point_selection_427.pts
;- GeoReferenced image : F:\new_invontory\2000\landasat\LE71480352000168SGS01_B8.TIF
;- DEM : F:\m_paper\declassified\aster_dgem_15m.tif
;Geographic coordinates of the GCPS with respect to the datum of the Georeferenced image
;Values : Easting, Northing, Altitude, X, Y, Weight, Opti, dE, dN, dA
;Note : Opti, dE, dN, and dA, are only used in GCPS Optimization
77.3237725666     35.6123505660    5197.0080   21173   19738   1.00000   1     0.0000     0.0000     0.0000
76.7315620102     35.8546380510    4632.4202    6072   15230   1.00000   1     0.0000     0.0000     0.0000
76.6717194872     36.0576428465    4063.3615    3774    9767   1.00000   1     0.0000     0.0000     0.0000
76.6957712608     36.3547811214    3576.6517    3015    1390   1.00000   1     0.0000     0.0000     0.0000
77.7460508289     36.1816804600    4363.4875   28100    1869   1.00000   1     0.0000     0.0000     0.0000
77.3161821847     35.1223364527    4522.2842   23438   33940   1.00000   1     0.0000     0.0000     0.0000
76.7032048620     35.2939772105    3192.2871    8165   31473   1.00000   1     0.0000     0.0000     0.0000
77.1626776351     36.2657127207    4652.0737   14147    1799   1.00000   1     0.0000     0.0000     0.0000
77.1087424950     36.1286301431    5310.5821   13540    5783   1.00000   1     0.0000     0.0000     0.0000
77.6950459412     36.0019549407    4744.4122   27881    7094   1.00000   1     0.0000     0.0000     0.0000
77.0882001187     35.8810130638    5121.3943   14282   12978   1.00000   1     0.0000     0.0000     0.0000
77.6508324976     35.8040678423    4811.5095   27876   12920   1.00000   1     0.0000     0.0000     0.0000
77.0465516733     35.4874330902    4933.4485   15242   24480   1.00000   1     0.0000     0.0000     0.0000
77.0915675068     35.7118004053    5497.1866   15183   17764   1.00000   1     0.0000     0.0000     0.0000
77.5327611426     35.5240384469    5175.3108   26560   21422   1.00000   1     0.0000     0.0000     0.0000
77.5166888959     36.2160627932    4466.8726   22615    1803   1.00000   1     0.0000     0.0000     0.0000
77.3268686449     36.0087205981    4825.0202   19246    8392   1.00000   1     0.0000     0.0000     0.0000
76.5793728882     35.7101486686    4724.5062    3183   19962   1.00000   1     0.0000     0.0000     0.0000
77.2341041566     35.2684307031    4747.5247   20767   30046   1.00000   1     0.0000     0.0000     0.0000
77.5038661365     35.3549546358    5520.0157   26758   26407   1.00000   1     0.0000     0.0000     0.0000
76.8751676303     35.2620875666    4175.5548   12305   31694   1.00000   1     0.0000     0.0000     0.0000
76.8152716311     36.2963713740    3714.3657    6011    2519   1.00000   1     0.0000     0.0000     0.0000

6

Re: KH9 Hexagon satellite images

Hi Haireti,

the focal length in your IO file is 30cm. This seems quite low for the KH9. You should double check that.

Francois