Mosaic Dataset - How to configure a time enabled derived mosaic dataset?

[JM32]

Good morning,

I have a collection of 10 source mosaic datasets (S_MDs) that I would like to add to a derived mosaic dataset (D_MD). The D_MD would then be used by GIS users in ArcGIS desktop software.

I've followed the imagery workflow tutorials on how to do this, have everything attributed with dates (year, first date, last date), and then added the S_MDs to the D_MD. My issue is the mosaic method is not working correctly (or maybe it is, but I don't fully understand what it's doing).

I'd like to have the most recent imagery shown on top by default (so 2023 in my case) when someone adds the D_MD to a project. What happens is once you are zoomed out far enough, various different years of imagery are shown and do not follow the most recent imagery rule. This would be very mis leading to users. The mosaic method settings I'm using are attached. I've tried a lot of different combinations with the same result...various S_MDs years being shown at different zoom levels.

I was under the impression if I had the By Attribute mosaic method being used, and had a Year field used, I could force the D_MD to show the most recent imagery on top regardless of zoom level.

Any help is appreciated!!

[CodyBenkelman]

Hi JM32

How are your overviews configured?  In this scenario we'd recommend you build overviews on the Source mosaics, and you'll have to ensure to copy appropriate fields to the overviews in the attribute table before ingesting them into the Derived mosaic.  Then do not build overviews on your Derived mosaic, and this should behave as expected. 

Note this assumes you don't have a large number of Source MDs.  If you do, then you may have performance problems rendering multiple Source OVRs when zoomed out.  If that's the case, then you'd change what I said above, and DO create OVRs on the Derived at an appropriate scale where your users can understand "if you zoom out to here, you'll just see the standard view of the project area, NOT the most recent imagery (at very low resolution) in every sub-area".  At some reasonable zoom scale, the difference between image dates is presumably (?) not relevant.  Note for the "standard view of the project area" you could choose to use a Landsat or Sentinel-2 scene etc. - swap out a good synoptic view for OVRs composed from your individual datasets 

If that doesn't make sense let us know.  

Cody B

[JM32]

@CodyBenkelman 

I built overviews on the source mosaics and skipped building any on the derived mosaic. There are a total of 10 source mosaic datasets. Prior to adding any source mosaics into the derived, I added fields to hold time information, and all records (primary imagery and overviews) have attributes for those fields. Right now, I have it working correctly until you're at scale 1:144,448; which is when the mosaic switches to an incorrect year. Then, once I go to the next scale zoomed out, it goes back to the correct most recent imagery. 

After I add the source mosaics to the derived, do I need to edit any of the fields in the attribute table? I noticed for example: the Category gets changed to Primary for all records regardless of if they are source imagery or overviews. I thought maybe it was getting confused due to that, or possibly it was having conflicts with cell sizes and was getting mixed up because of that. Although, I assume the By Attribute mosaic method ignores the cell sizes and should just sort based off the Year field I would like to use.

The second option offered makes sense - building overviews on the derived mosaic or using satellite imagery as overviews for when you're zoomed out enough. Before I try this out, I'd like to see if I can get the derived mosaic to work with what I have currently. 

Thanks,

Jon

[CodyBenkelman]

Jon

It sounds like you have your Source and Derived configured the way I would recommend - my only thought re: wrong source OVR image coming to foreground is that it might depend on exactly where your map is centered at the problematic zoom level. 

Have you built footprints for the OVRs?  That might be a bit tricky - in the Source MDs I think it will skip those where Category is not Primary, but once you ingest into Derived it may be slow to build footprints.  (I can't honestly recall if the BuildFootprints tool can skip all with existing footprints, therefore building ONLY for the Source OVRs now tagged as Primary.).  

The assignment of Category depends on context and desired behavior, but in this scenario I would leave them as automatically configured e.g. what were Source OVRs are now considered Primary in the Derived.  I don't believe you should have to edit any fields of the Attribute table in the Derived.  I would have thought that what you did should work properly so I'm not clear why it is not...  If I can think of other settings to change I'll respond again.

Cody

[JM32]

When the Source MDs were made, footprints were built on the OVRs. Attached shows the Derived MD with one of the footprints selected for the OVR of a Source MD.

I can play around with this this week and see if I have something configured wrong. I had it working for a different dataset - same type of relationship where I had Source MDs in a Derived MD. It works well but I will say it's for a much smaller region and only has a couple Source MDs in the Derived.

[JM32 · Accepted solution]

@CodyBenkelman

Cody - Just wanted to give you an updated on this thread.

I figured out what was going on with my Derived MD and why it was mixing up images/overviews at various zoom levels. It was all related to imagery cell sizes and how the setting called 'Cell Size Tolerance Factor' influences how images are mosaiced. 

From what I've read, this setting controls how imagery of different spatial resolutions are viewed in a mosaic dataset. In my case, the source MDs I am using vary in cell sizes (1 meter to 0.6 meter) and they also have different amounts of overview levels depending on the year. The original cell size tolerance factor being used was 0.8 (default value) in all of my Source MDs and then the Derived MD. I experimented with different values in this setting and found that when I place a very large value in this setting for the Derived MD, the mosaic method of sorting 'By Attribute' works as expected. It also fixed the issue when I enable 'Time' for sorting through the imagery. The value I used was 500, which I think kind of nulls out this setting in a sense and lets the mosaic dataset sort by the attribute I chose.

I originally followed this Esri Workflow for Imagery Management and must have missed the section stating to use a value of 999 for 'Cell Size Tolerance Factor' in Source MDs. 

Thanks again for the help earlier this fall.

Jon

ArcGIS Pro - Mosaic Dataset properties dialog showing cell size tolerance factor setting.