Add a warning to ocam2isis that the model is out of date

[jessemapel]

Description

The OSIRIS REx Image Processing Working Group has done extensive work to improve the OCAMs camera models. While they are working to contribute those changes back to the public release of ISIS, we should add a warning on ocams2isis that the camera model may not work well for highly precise processing such as color registration or millimeter scale mosaics.

As the improvements to the camera model come in, we should update the docs to reflect that. Related to #4060

Suggested Edit

The current documentation on ocams2isis is very sparse. It should mention that the distortion model and instrument position may not be correct. It would be good to also have the magnitude of the errors that these introduce so that users can make an informed decision about their needs.

Thanks!

[jessemapel]

I need to go over some documents that I have to collect the known errors and get a sense of their magnitude. I should have it ready before work starts.

[jessemapel]

Current known errors from OREx IPWG work that have been fixed in their version but not in the public version:

• Focal position dependent distortion for the PolyCam model is not implemented
• The current distortion is out of date, software changes are needed to use the OpenCV based distortion in the latest IKs
• The Struct SPK is not being used which accounts for the positions of the instruments relative to the center of the spacecraft. From the struct kernel docs this will result in an error of about a meter.
• Only specific sites have DSKs available. Software changes are required to load multiple DSKs at the same time. It is recommended that you only work within the extents of the DSK you are using. Use the dskbrief utility to view the lat/lon extents of your DSK file.

Based on all of these and what the IPWG team found, it is recommended that users don't attempt to do sub-meter processing until we can get the IPWG's fixes integrated.