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Author Topic: orthophoto size  (Read 3424 times)

emaxwell

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orthophoto size
« on: September 10, 2014, 04:00:04 PM »
Is there a practical limit to the size of an exported orthophoto? It seems that when the size exceeds 4 GB the export fails

Alexey Pasumansky

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Re: orthophoto size
« Reply #1 on: September 10, 2014, 04:03:16 PM »
Hello emaxwell,

Yes, for GeoTIFF format there's 4GB limit. For JPG there's 65535x65535 resolution limit.

For bigger orthophoto size we suggest to use Split in Blocks feature.
Best regards,
Alexey Pasumansky,
Agisoft LLC

JRM

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Re: orthophoto size
« Reply #2 on: September 10, 2014, 08:06:39 PM »
Alexey > do you plane on using libtiff 4.1 ? It supports this feature since 2007 and it has been used by GDAL since 2008.

andyroo

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Re: orthophoto size
« Reply #3 on: September 17, 2014, 03:45:16 AM »
I gave up on constraining my image output in PS and started exporting blocks without defining project bounds. I find it MUCH easier.

I have been getting good orthophoto results using gdal to make a .vrt (using gdalbuildvrt) from those blocks, then pulling out my AOI using gdal_translate to create tiled tiffs from the .vrt. You can make a bigtiff (>4GB) if you really want to by tweaking gdal settings (actually I think it does it by default if it calculates a >4GB tiff filesize). If I weren't sharing the imagery with others I'd probably leave it as a .vrt and build tiles that way.

My parameters (optimized for filesize, quality, and rapid display in ArcGIS, and I left the filenames in because I think they're mostly explanatory):

gdalbuildvrt -srcnodata 0 -vrtnodata 0 Elwha_20140812_merged.vrt 20140812_Elwha_RGBAvg_WGS84*.tif
gdal_translate -of Gtiff -co "COMPRESS=JPEG" -co "JPEG_QUALITY=90" -co "TILED=YES" -co "PHOTOMETRIC=YCBCR" -co BLOCKYSIZE=256 -co BLOCKXSIZE=256 -co "TFW=YES" -projwin -123.6118356 48.0112936 -123.5745359 47.9572204 -b 1 -b 2 -b 3 Elwha_20140812_merged.vrt Mills_20140812_RGBAvg_WGS84.tif

JRM

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Re: orthophoto size
« Reply #4 on: September 17, 2014, 10:52:03 AM »
yes, the default is set at 'IF_NEEDED". You can take -co blocksize out of your command as you are defining the default block size of gdal (256).