[MapServer-users] Varying use of overviews across Mapserver versions

[Dylan Beaudette]

Hi Everyone,

I've got identical GeoTiffs and .map files on two servers with varying
versions of Mapserver that is being used as a TMS. Mapserver 7.2.2 is (I
think) correctly using the overviews while Mapserver 7.6.4 is not.

Here is an example of the same file, tile, and styling applied across both
versions of Mapserver.

# Mapserver 7.2.2:
https://soilmap2-1.lawr.ucdavis.edu/cgi-bin/mapserv?map=/data1/website/ste/taxa.map&mode=tile&tilemode=gmap&tile=5+12+5&layer=blue9dylan&type=taxsubgrp&name=typic_xerofluvents&minvalue=5

Mapserver 7.6.4:
https://soilmap4-1.lawr.ucdavis.edu/cgi-bin/mapserv?map=/data1/website/ste/taxa.map&mode=tile&tilemode=gmap&tile=5+12+5&layer=blue9dylan&type=taxsubgrp&name=typic_xerofluvents&minvalue=5

It appears to me that the newer version is either ignoring or interpreting
the overviews differently. Each file has an internal tiling and overview
scheme like this:

----------------------------------------------------------------------------------
Band 1 Block=1766x4 Type=Byte, ColorInterp=Gray
  NoData Value=0
  Overviews: 883x1262, 442x631, 221x316, 111x158
----------------------------------------------------------------------------------

Does anyone have a clue about the differences? Is either version in error?

Thanks, and good to be back on the mailing list after a nearly 15 year
hiatus!
Dylan
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