[mapserver-users] double check - recommended way to optimize air photos for speed in MapServer while maintaining a decent quality and file size.

[Andy Colson]

On 02/10/2015 01:25 PM, Mark Volz wrote:
> Hello,
>
> In the past I prepared my air photos for MapServer by converting them into GeoTiff and creating compressed jpeg overviews.  I would like to double check if this is still a recommended method to prepare air photos that are fast, have a decent amount of quality, and are not terribly large.  If anyone has any comments on how I should prepare air photos for MapServer and possibly ArcGIS or QGIS let me know.
>
> Here is what I used in the past, which seems to work good:
>
> gdal_translate -CO TILED=YES -CO PHOTOMETRIC=YCBCR -CO TFW=YES -CO COMPRESS=JPEG -CO BIGTIFF=YES MNPIPE13-SID-9INCH.sid Pipe13.tif
>
> gdaladdo -r cubic --config compress_overview JPEG --config photometric_overview YCBCR Pipe2013.tif 2 4 8 16 32 64 128 256 512 1024
>
> I will be provided an ECW file, Mr Sid file, and I will be given the choice of getting either 775 individual jpg or tiff tiles.
>
> Thanks for any advice.
>
> *Mark Volz*
> >

Its what I'm using, but I'm setting jpeg_quality much lower than the default.  I ran several at different qualities and found next to no difference when zoomed all the way in.  For the gdaladdo I reduce the quality even more, because when your zoomed out, who cares if you can't make out an individual car.  I'm using:

gdal_translate -of GTiff \
   -co compress=jpeg \
   -co JPEG_QUALITY=60 \
   -co PHOTOMETRIC=YCBCR \
   -co tiled=yes \
   -co bigtiff=yes \
   --config GDAL_CACHEMAX 500 \
   src dest

gdaladdo -ro -r average \
   --config COMPRESS_OVERVIEW JPEG \
   --config JPEG_QUALITY_OVERVIEW 40 \
   --config PHOTOMETRIC_OVERVIEW YCBCR \
   --config INTERLEAVE_OVERVIEW PIXEL \
   --config GDAL_CACHEMAX 500 \
   dest \
   2 4 8 16 32 64 128 256 512 1024 2048 4096

I think (but no real measure) that too many small files or very few big files are slower than 12'ish files.  But that's just a gut feeling.

My Tama Iowa imagery is 30 gig, in 12 .tif files:

http://maps.camavision.com/map/tamaia?pin=14.27.203.003

The EWC version is 22 gig.  performance wise, when zoomed in as close as possible (car level), the ecw and tiff perform about the same.  When zoomed all the way out (entire county), once I added 2048 and 4096 to my gdaladdo, the tiff was almost a second faster than ecw.

If there are newer/better methods I'd be interested in them too.

-Andy