On 10.01.2018 20:33, Andrzej Popowski wrote:
i would be very defensive with interpolation in the case of missing values.
I got the same feeling. The best way to fill voids is to process whole HGT. And I believe that DEM providers already have done it, so any attempt at simple extrapolation would rather add errors than make output better. In my code I preserve voids. If requested coordinates are near void HGT node, then returned value is void.
Hi Andrzej,
From user perspective, I think it's more correct to somehow fill voids based of surrounding data than using elevation = 0. Elevation=0 I would only use as a fall back, if whole hgt-file is missing. I agree with you, that we shouldn't spent a lot of code for guessing.
To have a simple example: If there would be a cone-shape mountain in reality, but in DEM the top of the cone is missing, I would suggest to fill the hole with same elevation as the highest circle. So result in DEM would be a truncated cone shape. Of course reality is not that simple. :'( ;-) Henning