Bug report #18768

Nodata issue with TIN interpolation's cubic method

Added by Mathieu Pellerin - nIRV almost 2 years ago. Updated about 1 year ago.

Status:Feedback
Priority:Normal
Assignee:Marco Hugentobler
Category:Analysis library
Affected QGIS version:master Regression?:No
Operating System: Easy fix?:No
Pull Request or Patch supplied:No Resolution:
Crashes QGIS or corrupts data:No Copied to github as #:26655

Description

I've just spotted an interesting issue with the TIN interpolation code.

With the TIN interpolation "linear" method, the rendering is fine (tin-linear.png), but with the "cubic" method, the code inserts 0 values instead of nodata until it hits the first non-nodata value (see the black part at the top of tin-cubic.png).

Marco, you are our only hope ;) I've looked into the code, but couldn't get my way through it.

tin-linear.png (85.9 KB) Mathieu Pellerin - nIRV, 2018-04-19 12:38 PM

tin-cubic.png (84.6 KB) Mathieu Pellerin - nIRV, 2018-04-19 12:38 PM

test-data.zip (4.44 KB) Mathieu Pellerin - nIRV, 2018-04-19 12:42 PM

History

#1 Updated by Mathieu Pellerin - nIRV almost 2 years ago

Here's a simple test dataset. To replicate the above screenshot, use the "temp" field against a TIN interpolation alg using the cubic method.

#2 Updated by Marco Hugentobler almost 2 years ago

Hi Mathieu

Oh, that code is still in use? Most parts of the interpolation code are older than the QGIS project and not maintained anymore. I think you should replace it with a newer library for TIN/IDW interpolation.

#3 Updated by Giovanni Manghi about 1 year ago

  • Status changed from Open to Feedback

Please check if this issue is still valid on QGIS 3.4.5 or 3.6.

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