The header rows that say "FileName x" refer to the input image filenames, where x is an index number used to reference the filename throughout the rest of the GCP file. pts file extension and begins with the words "ENVI Rigorous Orthorectification GCP File." The first several rows that begin with semicolons are header rows. You can either create a Rigorous Orthorectification GCP file from scratch using your map and elevation data (see example below), or you can enter map/image coordinates and elevations directly in the Wizard and save it to the Rigorous Orthorectification GCP file format.Ī Rigorous Orthorectification GCP file requires a. Rigorous Orthorectification uses a specific GCP file format, which is an ASCII file that contains image file IDs, map X/Y coordinates, elevation in meters, and image X/Y coordinates. ![]() You may choose to bypass this step by clicking Next the orthorectified solution will be computed without GCPs in this case. The controls in this step of the Wizard allow you to optionally restore GCP files, to add new GCPs, and to edit existing GCPs. GCP elevations should be expressed in meters above mean sea level (orthometric height), not as height above the ellipsoid. For example, mid-latitude QuickBird scenes of a relatively flat area may provide an accurate orthorectification without the use of GCPs. Note: Be sure that your GCPs are of a quality that is consistently better than the initial accuracy of the sensor model this varies with data type and vendor. ![]() ![]() These points are called ground control points (GCPs). In this step, you associate image pixels to points on the ground whose locations are known through a horizontal coordinate system and vertical datum.
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