topic Re: Redundant overview files using mosaic dataset? in Data Management Questions

Redundant overview files using mosaic dataset?

ErikEndrulat — Tue, 15 Mar 2011 19:06:47 GMT

I have a large number of orthophotos in a compressed TIFF file format. These were compressed using FWTools, which created overview files (*.tif.ovr) for each image. I have created a Mosaic Dataset in catalog, and loaded the source rasters into this. The 'Add Rasters' tool in catalog builds overviews in a separate file folder.

My question is: Am I gaining anything by maintaining the overview files (i.e., *.tif.ovr) that were generated in FWTools, or are these completely superfluous to a Mosaic Dataset?

Thanks,

Erik

Re: Redundant overview files using mosaic dataset?

RobertBerger — Tue, 15 Mar 2011 19:11:04 GMT

Erik,

The overviews at the mosaic dataset level are different to the overviews (pyramids) at the dataset level. The pyramid (.ovr) files build by FWTools should still be used by the system. If you try to rebuild pyramids then these files should be replaced by files created by ArcGIS.
The overviews built by the mosaic datasets can encompass multiple source datasets, while the pyramids on the source can only exist one per each source dataset.
I hope this helps.

Robert

Re: Redundant overview files using mosaic dataset?

ErikEndrulat — Tue, 15 Mar 2011 19:23:12 GMT

Robert:

Thanks so much, this completely clears up my question. I didn't realize that the two levels of overviews were used by the system.

Erik

Erik,

The overviews at the mosaic dataset level are different to the overviews (pyramids) at the dataset level. The pyramid (.ovr) files build by FWTools should still be used by the system. If you try to rebuild pyramids then these files should be replaced by files created by ArcGIS.
The overviews built by the mosaic datasets can encompass multiple source datasets, while the pyramids on the source can only exist one per each source dataset.
I hope this helps.

Robert