What is better build pyramids or overviews in a mosaic dataset? Or do I need both

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10-28-2016 11:58 AM
MikeWunderlich2
New Contributor II

Hi GeoNet Community,

 

I am new on GeoNet and have a Question, do I need a pyramid and an overview for my content in a mosaic dataset?

 

I tried it by my own, I used 3 *.tif with a size of 9Gb and tested both...

 

"Case"

Space

*.tif (3 items)

9,07Gb

*.tif (3 items) + mosaic dataset + overviews

9,33Gb

*.tif (3 items) + *.ovr (3 items) + mosaic dataset + overviews

11,5Gb

 

Of course, if I do not build the pyramids the overviews would be more but the size of the overviews is small in comparison with the pyramids but where is the difference?


And I know that the loading of one tiff would take more time, but I will handle all tiffs as a mosaic.

Thanks a lot,

Mike

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JakeSkinner
Esri Esteemed Contributor
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JakeSkinner
Esri Esteemed Contributor
CarloFrate
Occasional Contributor

Has anyone found this link yet? Like Joe, I've read Part 1, but Part 2 is nowhere to be found.

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GuenterDoerffel
Esri Contributor

Hi,
I have not searched or found the link, but would like to give a very short answer to the general topic to clarify (hopefully):

PYRAMIDS are reduced resolution representations of SINGLE IMAGERY FILES. The main intention of pyramids is allow you to "see" this image in a broader scale range (and read less data for a given "scale").

OVERVIEWS are reduced resolution images that combine the area of potentially many images. They allow to "see" an area without the need to read and combine the data of potentially many images. The main intention of overviews is to take away the need to mosaic many images together for requests in large scales every time and to read less pixels in general. Reduced processing, bandwidth need, ...

Your question "do I need PYRAMIDS, OVERVIEWS or both" can not be answered in general for any usecase. It will depend on analytical needs, processing applied, data.
For optimized performance especially of Services, reducing the amount of file-reads and pixels to be processed is key. The best way to do this is OVERVIEWS. In many cases having NO PYRAMIDS but OVERVIEWS will be the most efficient solution. In cases where you need to identify single image source in a broader scale range, want to benefit from optimized resampling at any scale, have say frequent changes in base data and probably use a completely different dataset instead of overviews, pyramids might be useful, needed, good. So - it depends

Regards
Guenter

JoeBryant2
Occasional Contributor II

This link above is broken. I can find Part 1 of 2 on the new ArcGIS Blog site, but it looks like part 2 never got transferred over.

Overviews and pyramids: Part 1 of 2, What are they and why do I need them?