[COG] COG feedback based on foss4gna2018-cloudoptimizedgeotiffs-180518155909.pdf presentation.

[Panagiotis (Peter) A. Vretanos]

Hi,

I grabbed a copy of the foss4gna2018-cloudoptimizedgeotiffs-180518155909.pdf 
presentation and showed it to our developers.  This is the feedback they 
provided ...

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We handle overviews as separate files since people probably don't want us 
altering their source data and if there is a problem, we can easily blow away 
the overview files.

We put the GeoTIFF Tag Directories at the front of the file so the metadata for 
all of the contained images can be read in one gulp, but the presentation says 
to put the  TileOffsets and TileByteCounts inline with the Tag Directories. 
This may be problematic because these can be very bulky and interfere with 
reading all of the metadata in one gulp.

The presentation mentions compression but does not explicitly encourage it and 
it does not talk about alpha channels or masks at all, which are necessary in an 
environment where you are likely to combine images together.  For data that 
needs a user-specified Null Color, having built-in overviews is worthless, since 
the fringes of the overview data is blended with the background color which 
makes the result not match the Null Color and makes the fringe pixel values wrong.

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Sorry, I don't understand most of this but I am hoping that the people 
responsible for COG will find the feedback useful.

Ciao.

-- 
Panagiotis (Peter) A. Vretanos         CubeWerx Inc.
Big Kahuna (CTO, Senior DB Developer)  http://www.cubewerx.com
Tel. 416-701-1985  Fax. 416-701-9870   pvretano at cubewerx.com

"Smart people learn from everything and everyone.  Average
  people learn from their experiences.  Stupid people have
  all the answers." Socrates.