Wrong No Data Values

[kevinkreiser]

This is tile /N42/N42W072.hgt. Notice the white bits where (maybe two data sources abutted each other?) Their values are set to 32767 which looks a heck of a lot like -32768 but isnt that..so I'm not sure how to fix this in joerd (a pass to set anything outside of a range to the NO_DATA_VALUE maybe?) but this seems like a bug as the NO_DATA_VALUE should be -32768 for the SRTM3glv1 format

@zerebubuth do you concur?

[zerebubuth]

Looks like the interpolation between datasets at the boundary isn't working. In the image below it's clear that the +32767 pixels are at or near the change in resolution. At a guess, I'd say the interpolation is getting confused and returning +INF, which is being clipped to the channel maximum of 2^15-1. I think this is probably happening after the NODATA clipping, so possibly related to #41.