Best Method to Compress Raster Data for Easier Viewing

[JackieMauro]

I have been working on creating a raster data layer using mid 1900s aerial images. The images are physical copies which I have scanned into my computer as JPEGs and individually geofenced to their precise, present-day locations. After georeferencing them I used the merge raster tool to create one raster data set of all the georeferenced images. This raster data set is made up of over 150 single images, which makes Arc very slow to load and do any work in. I have more images to georeference and add to my larger raster set so I need to find a way to compress the one I have so I don't have to wait 20 minutes in between each click of my mouse. I have looked into the compress raster tool as well as the build pyramids tool, but I am still unsure how to use them correctly to get the outcome I want. The raster data I am using is RGB three band. I would like my new raster data layer to function as a basemap overlay so I can compare the historic imagery to the current day ortho photos and lidar imagery layers. 

[TravisSaladino]

This sounds like a job for Superman... oh wait.... the mosaic dataset!  

You can make it one in a file GDB that then references all the georeferenced jpegs in their original format (no merge raster tool needed) and then optimize the collection for display by creating what we call overviews for the mosaic dataset. Check out the led help topic at https://pro.arcgis.com/en/pro-app/latest/help/data/imagery/mosaic-datasets.htm, and feel free to follow-up with any questions. 

[JackieMauro]

I tried using the create a mosaic tool, which worked, then used the add raster to mosaic tool, which seemed to work, but once I get to define overviews and build overviews something seems to be going wrong. The boundaries of the mosaic tool show up but when I try to make the imagery is visible, it just shows large black and white checkered squares instead of the pixelated imagery. Am I still using the wrong tools or the wrong process or do you think I am doing something wrong in the way I am defining it?

[TravisSaladino]

You are using the correct tool.

The topic at https://pro.arcgis.com/en/pro-app/latest/help/data/imagery/mosaic-dataset-overviews-pro-.htm could also be helpful. Usually as a test, I'd say use the https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/build-pyramids-and-statistic... tool. That might help.

If it doesn't fix it, could you post a screen capture of what you are seeing. I think I understand, but I'd like to confirm before I suggest anything else. Thanks.

[JackieMauro]

When I use the mosaic tool, add the rasters, and then try to define the overviews, I am getting this checkered pattern instead of the pixelated imagery like shown to the left of the mosaic. 

[TravisSaladino]

Ah ha. Check out https://support.esri.com/en-us/knowledge-base/problem-mosaic-datasets-display-a-checkerboard-pattern.... 

[JackieMauro]

I have been messing around with it all day and still have had no luck. I'm wondering if this problem stems from the fact that the whole map document is saved onto a shared drive but the raster files, I have been georeferenced were initially saved and imported directly from my desktop? My desktop files automatically load into the shared drive, but I think they are still in different locations. This may be an obvious answer to you, but I am not used to dealing with Arc stuff that is this data heavy/deals with different pathways.  

[TravisSaladino]

We've all been there Jackie. I would have some time today to help out. But it would probably most efficient if we could use a screen sharing option like Teams or Zoom. I can get you my email address if you want to do that. 

Or provide screen captures showing the catalog window or file explorer with the path to where the geodatabase is that has the mosaic dataset and another with  the folder where the jpgs are. 

[JackieMauro]

I'm not too sure what my availability looks like today so far. I may be around this afternoon but most likely not this morning. I will attach photos with the paths of the mosaic, raster layers, and geodatabase and maybe that will help clear things up. I can tell this is close to being resolved, I am still just missing something. I also reached out to my city's GIS manager to see if they had any tips and I am waiting to hear back from them (they are usually very slow to respond which is why I took my issue here first). 

[TravisSaladino]

Those help a ton. I think the issue could be either OneDrive or the "special" characters in the path name. Try this...

1. Move the source jpgs to a local folder (maybe make c:\myGISData or something like that)
2. make a new file GDB at directory too.
3. Then go through the whole workflow again, making the mosaic dataset in the new GDB
4. and then create the overviews. 

Sometimes OneDrive will only store files in the cloud and other times they are local on your computer, and it can be hard to figure out exactly where things are. By doing this you know that everything is on your computer and ArcGIS Pro should be able to get to everything it needs.