How to retain RPC information from the original input file for orthorectification: ASTER example

There are occasions where pre-processing needs to take place prior to orthorectifying data. However, after the file is processed in ENVI, the orthorectification tools will prompt you for the RPC file because the necessary tags from the original file are no longer present or associated with the processed files. In the case of ASTER or SPOT data, the RPCs are calculated in ENVI from the information contained in the original files so no external source for the RPCs exist and orthorectification cannot be performed.

In the case of ASTER or SPOT data, if you wish to retain the calculated RPC information, it is necessary to store this information in an ENVI file header prior to processing the data. This can be achieved by performing the following steps:

• Open the ASTER or SPOT data.
  
• Go to File ->Edit ENVI Header ->Edit Attributes ->RPC or RSM Projection Emulation.
  
• In the RPC parameters dialog, toggle the RPC Projection Emulation Enabled to 'On'. Then select OK to exit this dialog and OK again to retain the new header settings.

The above steps will prompt ENVI to calculate the RPCs and write them to an ENVI header file (.hdr) in the same directory as the original file. Then process the data as you wish in ENVI. The RPCs in the header file will be passed on to the newly processed file and orthorectification can be performed.

Review on 12/31/2013 MM