I'm attempting to interpolate the NU national grid square of Ordnance Survey's terrain data (10m intervals). If I interpolate with IDW, I encounter no issues and the raster pixels are square in shape as they should be. When interpolating with TIN (much better for conducting viewsheds over) the NU national grid square returns non-square pixels after the interpolation process. When using the viewshed plugin this creates obscure viewshed as shown here. Can anybody else confirm you receive non-square pixels?
When trying to fix this, I was given an error "wkb access out of bounds".
This error has been appearing more and more ever since I first encountered it to the point where its occurring consistently with every TIN interpolation. I have tried the following:
restarting QGIS and the computer
different national grid squares
meticulously gone over CRS selections
checked the validity of the contours
clipped the contours to smaller areas
downgraded my version of QGIS - all at no avail.
I'm using QGIS 2.18.10. I'm conducting the TIN interpolation by navigating to
Raster > interpolate and using the viewshed plugin (or would have been if the interpolation worked).