Hi, 1) It's a mistake. You can use lat/lon multiple. Only this tiles you can merge. But i think, that's useless. It's better to take the necessary results and merge this with osmosis (see https://github.com/FSofTlpz/Hgt2Osm2/blob/master/README.md) 2) Oops, a stupid error. Usual i don't use lat/lon. Using --HgtPath is easier for me. 3) Unfortunately i can't reproduce this effekt. You have probably do that (?): hgt2osm --HgtPath=E:\Dem\All_UK_HGT_Data\ --Mergefile=e:\devonall2.osm The prog take then all HGT's in the hgt-path, produce files like clN40W006.osm.gz and at last e:\devonall2.osm. I see "==> Lese Ausgangsdaten 49° -4° ...". Have you really a file N49W004.hgt.zip or S04E049.hgt.zip? I think, that's all water between france and GB or eastwards from africa. I have updated the prog. Frank