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Author Topic: No value -32767  (Read 11365 times)

Kjellis85

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No value -32767
« on: June 14, 2012, 12:48:28 AM »
I know others (and myself) have discussed this topic before but I don't feel that there has been any real solution or explanation as to why it is necessary. What I am talking about is the no data value in DEM export. I have a way of removing the negative values of -32767 from the DEM post-photoscan, but I am interested in finding out if it is possible to get rid of this altogether without having to apply external workflows to the data. I have tried exchanging the -32767 value with other positive numbers, but when opening the raster file in GIS the negative value is always there. Have anyone given this any thought? Alexey, are you guys aware of this?

Diego

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Re: No value -32767
« Reply #1 on: June 14, 2012, 03:38:27 AM »
Again with the same  :o, do not understand why you whine so much of this, I see no problem in the workflow.  ;D

andyroo

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Re: No value -32767
« Reply #2 on: June 14, 2012, 11:33:19 PM »
@Kjellis85: I think what you need to do is put the right NoData value in when you export the DSM from Photoscan.

For example, in ArcMap, if you export a 32-bit floating point GeoTiff, Arcmap is expecting a NoData value of -3.402823466e+38 and if you use this as your nodata value you don't need another step.

Kjellis85

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Re: No value -32767
« Reply #3 on: June 15, 2012, 12:30:03 PM »
@Kjellis85: I think what you need to do is put the right NoData value in when you export the DSM from Photoscan.

For example, in ArcMap, if you export a 32-bit floating point GeoTiff, Arcmap is expecting a NoData value of -3.402823466e+38 and if you use this as your nodata value you don't need another step.

If this is true I will owe you big-time! I'll check it as soon as I am able to.

Kjellis85

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Re: No value -32767
« Reply #4 on: June 15, 2012, 01:32:23 PM »
Did a quick test using QGis and it sort of worked. I had to use a value of 2.14748e+09, but I guess that is proprietary for that software and that -3.402823466e+38 only applies to ArcMap. However, when I did this in QGis the maximum value got set to the same as the NoValue, ergo only shifting the problem from one end to the other. I will fo a test with ArcMap to see if it acts any differently.

Kjellis85

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Re: No value -32767
« Reply #5 on: June 16, 2012, 01:47:12 PM »
Works like a charm in ArcMap, no more post-processing of the data:) Thanks andyroo!