- Multi-Instrument Registration
Reasons for merging datasets¶
List of useful reasons:
- Change detection
- Spatial / Spectral merges
- Understanding instrument calibration (optical distortion, radiometric similarities)
- Multivariate statistical analysis
- Principal component analysis
- Etc., etc., etc.
Choosing the "truth"¶
Datasets from different instruments often do not register using the raw, native pointing. In order to merge these datasets, they must be brought together by selecting one dataset as having the correct pointing or “truth”. The pointing for the other datasets is then adjusted to match the truth.
Choosing the truth is dependent on the datasets being merged. First, the data with the known best pointing could be chosen, such as the Mars Global Surveyor’s MOLA. Or if simply merging HiRISE and CTX, HiRISE pointing is considered to be more accurate than CTX pointing.
The differing resolution of the datasets is something to keep in mind. You will not want to attempt to register HiRISE directly to MOLA as the difference in resolution is too large to find a common point. In general, you will want to build up in resolution.
- MOLA (Lowest Resolution)
- MOC WA
- MOC NA
- HiRISE (Highest Resolution)
- Updates camera pointing for a single image
- Tie one image to another
- THEMIS to MOLA, HiRISE to MOC NA, HiRISE to CTX, etc.
- Simultaneously updates camera pointing for multiple images
- Typically used for regional or global mosaics
Start with Experiment Data Records (EDRs) if possible to ensure consistency among the datasets for SPICE and mapping parameters such as planetocentric vs planetographic and positive longitude east vs west.
Merging THEMIS / CTX / HiRISE (controlled to MOLA)¶
Controlling THEMIS to MOLA¶
Start with the lowest resolution dataset, which in this case is THEMIS. Pick a matching point between THEMIS and MOLA using qview. (Hint: It is easier to use a crater as a match point.)
Write down the latitude / longitude of the point on MOLA and the sample / line of the point on the THEMIS image. Update the THEMIS pointing by running the ISIS3 program deltack.
deltack from=themis.cub lat1=molaLat lon1=molaLon samp1=themisSamp line1=themisLine
This will update the themis pointing to the MOLA.
Controlling CTX to THEMIS¶
Next, control the CTX image to the THEMIS image by picking a match point the same as was done between the MOLA and THEMIS. Use the THEMIS image that has the updated pointing (after deltack).
deltack from=ctx.cub lat1=themisLat lon1=themisLon samp1=ctxSamp line1=ctxLine
Controlling HiRISE to CTX¶
|Registration Errors: ~ 40 samples, ~ 20 lines|
First, control the HiRISE red ccds locally by running the ISIS3 program, autoseed, which will automatically pick match points among the red ccd’s. Then run the ISIS3 program, pointreg, which will sub-pixel register the points that autoseed picked.
Next, pick a matching point between HiRISE RED5 and the CTX image with the updated pointing (after deltack). Record the CTX latitude / longitude and the red5 sample / line. This will be used as a ground point when running jigsaw on the red CCDs to adjust the pointing.
In order to use this point as a ground point, the radius is needed. Run the ISIS3 program, campt to get this radius.
campt from=ctx.cub lat=cxtLat lon=ctxLon type=ground
This ground point can now be added to the control net file that was output from pointreg using any editor.
Object = ControlPoint PointType = Ground PointId = Ground_1 Latitude = -5.3320739040534 Longitude = 213.71209674872 Radius = 3394090.9408245 Group = ControlMeasure SerialNumber = MRO/HIRISE/RED5/848376111:51904/2 MeasureType = Automatic Sample = 1131.92 Line = 18555.3 ErrorLine = 0 ErrorSample = 0 ErrorMagnitude = 0 DateTime = 2007-05-25T09:24:50 ChooserName = "TLS" GoodnessOfFit = 0 Reference = True End_Group End_Object
Finally, run jigsaw on the HiRISE red cubes.
- controlled mosaics
|MOC Registered with HiRISE Red CCDs||MOC Registered with HiRISE Red CCDs (zoomed)|
Project the THEMIS, CTX and HiRISE red images using the CTX resolution and latitude / longitude range.
cam2map from=ctx.cub to=ctx.equi.cub pixres=mpp resolution=5.0 map=$base/templates/maps/equirectangular.map cam2map from=themis.cub to=themis.equi.cub map=ctx.equi.cub pixres=map defaultrange=map /bin/ls *RED* | sed s/.balance.cub// > red.lis cam2map from=\$1.balance.cub to=\$1.equi.cub map=ctx.equi.cub pixres=map defaultrange=map -batch=res.lis /bin/ls *RED*.equi.cub > redEqui.lis automos fromlist=redEqui.lis mosaic=redMos.cub match=no
More Information: Learning About Map Projections
Problems and Issues¶
Registering to MOLA can be difficult:
Simultaneous CTX and HiRISE observations do not register
- Inconsistent sample/line offsets
- Probably have timing issues
- Maybe some boresight misalignment
- Will research this problem as more CTX data becomes available
MOC Narrow Angle does not align with HiRISE or CTX
- Update the MOC NA focal length
- MOC NA camera model has no distortion model
- More research needed in this area
- Unable to fully decipher the PDS IMAGE_PROJECTION_OBJECT
- No CRISM camera model in ISIS3
- Unable to compare HiRISE, MOC, and THEMIS to CRISM