Co-Registration Shift Assessment

The assessment of the co-registration shift of ATSR data follows the ideas laid out in Moroney et al. (2002) for MISR. The workflow is as follows:

Image Normalisation
Creation of a spatial filter (optional)
Stereo Matching using M4 or M5
Computation of expected disparities
Creation of a clear land mask
Computation of residual registration shift

Interactive Use

The initial steps are identical to the computation of cloud-top height and are not repeated here.

Expected disparities are computed from elevation data contained in the ATSR product. A sample result, this time showing the Red Sea (The usual test-scene does not have enough variation in elevation to demonstrate the operator), is shown in the following figure:

BEAM showing Expected Disparities result image.

A clear land mask is computed by the Clear Land Mask operator.
The results from the previous operations are then combined to calculate the residual disparity which should give an indication of the co-registration shift using the operator Image Coregistration. This is illustrated here:

BEAM showing Image Coregistration operator and a result image, with constrast stretched.

Batch Use

As for the cloud-top height retrieval the image registration can also be computed in batch mode with the GPT command. The graph description file will need to be similar to this: coregistration.xml

The batch processing is called with parameters as before:

gpt.sh coregistration.xml -t output.dim -SatsrToaL1b=ATS_TOA_1POLRA20030401_024113_000062202015_00103_05668_0591.N1