Parent Topic: GCP Collection

Saving GCPs

GCPs can be saved in the GCP Collection step by selecting the ``Save GCP ...'' menu item on the File menu on the GCP Collection Panel.

GCPs are saved to an existing or new PCIDSK auxiliary segment. If the georeference system defined for collecting GCPs is not a simple projection and the GCP georeference system can be projected and the "Mathematical Model" selected for the "GCPWorks Setup" panel is not "Satellite Ortho Correction", the GCPs will be reprojected to equivalent LONG/LAT values before they are saved. (See the LONG/LAT subtopic for more details.)

If more GCPs were to be added in a future GCPWorks session, the georeference system for collecting the GCPs should be set up before loading the existing GCPs. Then the LONG/LAT GCPs would be reprojected to that georeference system when they are read in.

The ``Save HI-VIEW Ground GCPs'' entry can be used to save the geocoded GCPs to a file named ground.dat in HI-VIEW format. The ``Save HI-VIEW Mono GCPs'' menu selection can be used to save the uncorrected GCP coordinates to a file named photo.dat.

The ``Save HI-VIEW Stereo GCPs'' entry can be used to save the current uncorrected and master GCPs in a HI-VIEW format photo.dat file. This option should only be used in Image To Image tiedown if both images are in pixel/line coordinates.

LONG/LAT
GCPs are NOT converted to "LONG/LAT" by GCPWorks for the following simple projections units:

GCPs are NOT converted to "LONG/LAT" by GCPWorks because they are not reprojectable:

GCPs ARE converted to "LONG/LAT" by GCPWorks for the following non-simple projections if the "Mathematical Model" selected for the "GCPWorks Setup" panel is NOT "Satellite Ortho Correction":

GCPs saved to disk as LONG/LAT and used outside of GCPWorks may have to be reprojected with the GCPPRO program. For example, the following steps would be required for producing "TM" GCPs for the SRORTHO program: 1. "TM" GCPs saved to disk from GCPWorks would be converted to equivalent 

   "LONG/LAT" coordinates.
2. Convert the equivalent "LONG/LAT" GCPs to the output "TM" system 

   with GCPPRO.
3. Use the "TM" GCPs produced from GCPPRO as input to REG.

ERRORS
The following errors are possible when attempting to save GCPs.


Write Permission
The following message is produced when the selected database file to which the GCPs are to be saved cannot be opened with write access. Typically this is a UNIX permissions problem that must be rectified outside of GCPWorks.

``Unable to open database `xyz' with write permission.''


Non-PCIDSK File
Currently, GCPs can only be stored in PCIDSK file auxiliary segments. Any attempt to save them to another database file type will result in the message:

``Unable to save GCPs to a non-PCIDSK file.''


Corrected GCP Georeferencing Illegal
The georeferencing system of the corrected GCPs must either be PIXEL or match the georeferencing of the selected geocoded database or geocoded area. The following message will be generated:

``Unable to use geocoded GCPs with a georeferencing system of:%s''


Uncorrected GCP Georeferencing Illegal
The georeferencing system of the uncorrected GCPs must be PIXEL. If it is not the following message will be generated:

``Unable to use uncorrected GCPs with a georeferencing system of:%s''

Parent Topic: GCP Collection
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