Why does coregistration of complex SLC datasets result in floating point images in SARscape?

When using the Coregistration tool from the Basic menu in SARscape on SLC (complex) data the resulting coregistered files are floating point (amplitude) images.  These images cannot be used for interferometric processing since they do not contain all of the original complex data.  However, the Interferometric process also includes a coregistration process which does produce complex output.  Why is there a difference in these tools?

Answer:
The coregistration function that is available from the basic module is typically used for preparing stacks of amplitude data for later (amplitude) processing such as speckle filtering, geocoding, and classification.   These coregistered datasets cannot be used for interferometry where you also need the phase information.  So while the coregistration and the interferogram generation modules both make use of the same base coregistration functions, the basic coregistration process is used to generate amplitude products and the inteferometric module will generate the complex output required for interferometry.  In most cases, the final goal of coregistering SLC images is to obtain an interferogram, so there is no reason to store the coregistered SLCs as separate, additional output during interferogram generation. 

There are cases when generating interferograms that the coregistration of images fails and causes an error in the interferometric process.  In some cases it can be useful to try the coregistration from the Basic menu separately to determine the cause of the errors in coregistration without running the full interferometric process.  Once the issue is resolved, the full interferometric process can be attempted again.

Review on 12/31/2013 MM