topic Re: No Data gaps in Imagery and Remote Sensing Questions

No Data gaps

SLouq — Mon, 15 Mar 2021 18:22:37 GMT

Hi,

I've built my mosaic dataset out of two mosaic datasets each with different resolution imagery. It looks great but I have gaps of No Data (little white strips) where the footprints from of one of the datasets lies. It only appears at certain scales though. How can I eliminate these No Data strips?

Re: No Data gaps

Todd_Metzler — Mon, 15 Mar 2021 18:25:10 GMT

Hello,

Common if Spatial Reference Systems and/or applied MDS transforms don't match. Check these settings in your source data and MDS.

Todd

Re: No Data gaps

PeterBecker — Mon, 15 Mar 2021 20:43:15 GMT

If you include a screen shot of what you are seeing it will be easier to identify the issue. At what scales to you or don't you see these gaps? If you load the two as separate datasets in Pro do you also see gaps? If the gaps appear at the smaller scales the issues could be related to the pyramids in the dataset and how they were created. Each pyramid level is typically 1/2 resolution of the previous. If the number of rows/columns is not divisible by 2 then the apparent image may shrink by 1 pixel, which can appear as a gap if there is not overlap between the images. This is why it is always better to have some overlap between datasets that are cut into tiles. The other issue maybe related to if the image is being clipped by footprints or boundary. Check following settings

Clipping the imagery by footprints or boundary is an optimization (especially for overlapping images), but if they are not defined well then they can results in gaps. Try turning the clipping off to see if this is the case.

Remember if you have generated overviews then then the overviews would have been created based on the settings when the overview was created, so you may want to exclude them or use lockraster on the source images to see the effect without overviews

Re: No Data gaps

SLouq — Mon, 15 Mar 2021 20:55:53 GMT

The gaps appear when I zoom in and disappear when I zoom out. Of the 2 suggestions you suggested, the 2nd one sounds more probable. Attached is two screen shots showing the gaps

Re: No Data gaps

PeterBecker — Tue, 16 Mar 2021 03:06:28 GMT

Yes, looks like an issue with either the source images not actually being 100% connected or footprints clipping and the projection of straight lines causing some artifacts. Also consider using the merge option on each set of source dataset. This will virtually merge the images into a single item the mosaic dataset. Don't go overboard on this. IE try to keep the number of rasters per merge to <100.