Author Topic: large aerial photography, Best file format/compression and ECW issues  (Read 403 times)

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Rod

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We received 2.6TB with of aerial photography files in GeoTIff (with packbits compression) and its too big to store and too unwieldly to use in Autocad.
I am going to reproject and convert to an appropriate format and compression.

I am thinking either
ECW or
Geotiff with JPEG compression http://blog.cleverelephant.ca/2015/02/geotiff-compression-for-dummies.html

My initial tests with the GeoTiff have good compression but they still seem slow to load in Autocad, once loaded they are quick

In the past we have used a single ECW file covering about 4000km2 the file is about 53GB and doesn't seems to have a problem with quick loading, zooming and panning.
I have had issues (2019 and earlier) with printing from a rotated viewport either to paper or PDF that the image is shifted from its correct position.
In my tests with 2020 I haven't had this issue with ECW files, but because it is intermittent I'm not sure if its fixed.

Has anyone done any testing with different image formats and compression in Autocad?

Cheers, Rod.

« Last Edit: August 20, 2020, 07:26:22 PM by Rod »
"All models are wrong, some models are useful" - George Box

Rod

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Re: large aerial photography, Best file format/compression and ECW issues
« Reply #1 on: August 20, 2020, 12:03:01 AM »
Geotiff 1km2 JPEG compression 50% quality, 47MB stored on local SSD loads in 3mins 20s
ECW 3000km2 Compression Target 5%, 53GB over the network, loads in 1s

With the Geotiff the CPU is hardly working, I was expecting it to be near max

Tested on Autocad Civil 2019
« Last Edit: August 20, 2020, 07:26:50 PM by Rod »
"All models are wrong, some models are useful" - George Box