All,
I believe that there could be a bug in the PDIST function in gmt6. The plot attached shows a simple function calculating the distance (in projected coordinates) to the centre of the plot in both gmt5 and gmt6 (grdmath PDIST). In gmt6, it appears like the function returns the square of the distance rather than the distance.
Maarten
Yes, you are right. Trying to figure out why it snuck in there. It must have been some misguided attempt at being clever and faster. in gmtselect we do this to avoid taking square root of a squared distance since we only are comparing them to a fixed squared distance. in PDIST this obviously makes no sense. PR coming soon,
Bug fixed in gmt master now. Thanks for pointing it out - I have added a test to warn us if this should happen again!