Re: [Qgis-user] Clipping a Raster with a Mask Layer

[Kurt Menke]

Hi Randy,

I used the GDAL clip raster by mask layer tool and got the same result you
did. I then tried the Saga Clip raster with polygon tool and it worked
perfectly.

Kurt 

 

**

Kurt Menke, GISP

Bird's Eye View 

  www.BirdsEyeViewGIS.com 

Work: 505-265-0243

Cell: 505-362-1776

 

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Re: [Qgis-user] Clipping a Raster with a Mask Layer - update - possible bug

[Randal Hale]

So I've got an update on this.

If I run this with the command line (gdal 2.1):

gdalwarp -cutline acid_forest_buffer.shp low_east.tif output.tif
/Processing input file low_east.tif.//
//Using internal nodata values (e.g. -3.40282e+38) for image low_east.tif.//
//Warning 1: Self-intersection at or near point 2309.5402184630693 
1121.2793755624425//

//ERROR 1: Cutline is not valid after transformation/

I had one community member confirm the clip works in 2.14.1. I think 
ultimately this is a gdal version problem - sort of.


If I look at the shapefile in QGIS I get an error using the topology 
tools looking for overlaps. I seem to have 2 multipolygons in this data. 
I clean those up and the tool runs as expected.


Is there something with gdal 2.1 that chokes with a multipolygon in 
running this type of clip against a raster?



On 10/07/2016 09:27 AM, Randal Hale wrote:


I've tried this on:

  * 2.14.6 on Windows
  * 2.16.3 on Linux
  * Master on Linux

Dropbox Link: 
https://www.dropbox.com/sh/zg8miobad8ax0ef/AABXzPzTd8920I248_IprKjba?dl=0


I have a raster and polygons. All matching in projection. M one worry 
is the raster is a float32 tiff and something it wrong with it. I 
didn't create the raster but I am trying to help someone work their 
way through this exercise for a College Class.


When I use the processing tool to clip the raster with the vector I 
get an output image that in the legend shows the values as being nan - 
which I guess is null. No matter what I do - there is no clip. Just a 
large image that is black or nan (null).


Thoughts? I'm stuck. I don't know if I'm seeing a bug or I've got a 
bad image. The person originally working through this said it all 
works correctly with 2.8 (but I haven't attempted that version as of 
yet).


Randy

--

Randal Hale
North River Geographic Systems, Inc
http://www.northrivergeographic.com
423.653.3611rjh...@northrivergeographic.com
twitter:rjhalehttp://about.me/rjhale
http://www.northrivergeographic.com/introduction-to-quantum-gis
https://www.facebook.com/NRGSInc


--

Randal Hale
North River Geographic Systems, Inc
http://www.northrivergeographic.com
423.653.3611 rjh...@northrivergeographic.com
twitter:rjhale http://about.me/rjhale
http://www.northrivergeographic.com/introduction-to-quantum-gis
https://www.facebook.com/NRGSInc

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[Qgis-user] Clipping a Raster with a Mask Layer

[Randal Hale]

I've tried this on:

 * 2.14.6 on Windows
 * 2.16.3 on Linux
 * Master on Linux

Dropbox Link: 
https://www.dropbox.com/sh/zg8miobad8ax0ef/AABXzPzTd8920I248_IprKjba?dl=0


I have a raster and polygons. All matching in projection. M one worry is 
the raster is a float32 tiff and something it wrong with it. I didn't 
create the raster but I am trying to help someone work their way through 
this exercise for a College Class.


When I use the processing tool to clip the raster with the vector I get 
an output image that in the legend shows the values as being nan - which 
I guess is null. No matter what I do - there is no clip. Just a large 
image that is black or nan (null).


Thoughts? I'm stuck. I don't know if I'm seeing a bug or I've got a bad 
image. The person originally working through this said it all works 
correctly with 2.8 (but I haven't attempted that version as of yet).


Randy

--

Randal Hale
North River Geographic Systems, Inc
http://www.northrivergeographic.com
423.653.3611 rjh...@northrivergeographic.com
twitter:rjhale http://about.me/rjhale
http://www.northrivergeographic.com/introduction-to-quantum-gis
https://www.facebook.com/NRGSInc

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