Preprocessing requirements

Before running this module, the following requirements must be met to ensure the job processes successfully and produces accurate results:

• Math models: The imagery specified for orthorectification must contain a valid math-model segment.

  The math-model segment can be:

  • The nominal math-model segment, as imported with the raw data using the Data Ingest module
  • A refined math-model segment created by the GCP Collection module or the Tie-Point Collection and Refinement module
  • A refined math-model segment developed in OrthoEngine and exported to the imagery
  Depending on the input imagery, however, not all images will contain a valid math model. For example:

  • When a sensor is used in which the MS and PAN images are coregistered directly from the sensor (for example, IKONOS, QuickBird) and the MS and PAN files are present, the Orthorectification module automatically reads the math model in the PAN file, and automatically computes the corresponding rational functions model for the MS scenes. This is because there is a direct and established relationship between the rational-function coefficients for PAN and MS data sets. When the math models are computed, both image types are then orthorectified automatically.
  • When the sensor being used does not have a direct relationship mapping the panchromatic rational-function coefficients to the multispectral rational-function coefficients (as with SPOT 5), and both MS and PAN files are present, the Orthorectification module automatically orthorectifies the PAN image first, then performs automated GCP collection routines to coregister the MS image to the PAN image. Finally, the MS image is orthorectified. When a stereo scene has multiple files, such as nadir, backward, or forward, the nadir panchromatic image will be selected for coregistration.

• Imagery: The specified input imagery must have been ingested into CATALYST Enterprise with the Data Ingest module. This ensures that the imagery can be read by subsequent CATALYST Enterprise processes, and that the input files adhere to the CATALYST Enterprise file-naming convention.

• Digital elevation models: A digital elevation model (DEM) is required to perform orthorectification. The specified DEM must be in a GDB-compatible format and should cover the full extents of the imagery requiring orthorectification. To ensure a highly accurate orthorectified image product, the DEM should be as accurate as possible. The DEM can be supplied as a single file, or a folder of individual DEMs.

• File-naming convention: The module reads the input scenes folder for images containing the term "_RAW"; a tag created by the Data Ingest module. If this tag is not present in the file names, the Orthorectification module will not orthorectify the imagery.