MrSID imagery used to work but suddenly has wrong extent

Question

I'm struggling with a mysterious problem with imagery extent.  I do not know much about managing imagery files. We have a few sets of aerial imagery of our region (MrSID files), stored on ArcGIS Server, and all the imagery was working/displaying fine, until one set randomly started displaying on the other side of the country. No one was doing any work on it; this seemed to happen truly randomly.

I found that most of our imagery sets have a projection that uses feet as the unit, while the problem set uses meters. However, the extent of the problem set consists of numbers that would be correct if the units were feet!

I created a polygon feature class for troubleshooting/testing, and gave it the same extent problem as the imagery. I could successfully fix it, then, using the GP tool Add Spatial Index. However, it appears this tool can only be used on feature classes, not rasters/imagery.

My current idea for fixing the imagery extent is: copy/record the current extent (the numbers that would be good if the projection units were feet), then project the imagery into the same projection but the variation that uses feet instead of meters, then manually edit the extent in Catalog to use the original extent, which will hopefully work now that the projection units are feet.

But who knows if that method would work or run into unforeseen errors. I can try on a copy of a small part of the imagery.

My question is, does anyone have a better solution for fixing the extent?  And does anyone know how this problem could have occurred so randomly?? like a bug or something?

AllenDailey1 · Answer

I have a solution that seems to be working - the Define Projection tool - but it's still a total mystery why the imagery became located thousands of miles away from where it should be.  If anyone has ideas as to how this could happen, I am really interested to hear.

One clue is that I discovered that the imagery in question displays in the correct location in ArcMap - just not in ArcGIS Pro!  This suggests that the imagery's projection/coordinate system is being handled or interpreted differently by ArcMap and Pro.  ArcMap recognizes the coordinate system units as US Survey Feet, which is what allows it to be placed in the right location, while Pro thinks the units are meters, which puts the imagery in the wrong location.

In the XML file that goes with the MrSID file for this imagery, the projected coordinate system is "NAD83 / California zone 5," ID number 26945.  The imagery is from 2007, so it was configured long before ArcGIS Pro existed.

For our imagery from other years, they all use State Plane California zone 5 too, but with a slightly different coordinate system ID, such as 2229.

AllenDailey1 · Answer

Thank you for your suggestion!

After more investigation, I found that the Define Projection tool worked on a small area of the raster that I made a copy of for testing.  I tried this tool because I got the sense that the projection was kind of there but kind of broken.  I think Project or Project Raster may have kept the raster in the same location even while changing the projection.  With Define Projection, the raster got moved across the country to the precise correct location, so I will probably use this, going forward.

JonM32 · Answer

@AllenDailey1

I would give the Project Raster tool a try: Project Raster (Data Management Tools) | ArcGIS Pro documentation

It allows you to reproject the raster to another projection. That way, you won't have to manually copy and paste values and it's much simpler. It will make a new raster when you run it, so it may take a bit of time to run depending on how big your imagery is. For a new format, a TIFF is a good choice with bilinear resampling (makes it smooth looking compared to nearest neighbor, runs faster than other options too).