Is it generally safe to move a coastline more inland if aerial imagery shows it’s so?

Beakerboy · 2024-06-21T12:16:28.532Z

I recently visited Olympic National park and was on Second Beach during a low tide period. This day was not supposed to be exceptionally low, but the OSM coast in the area is MUCH further out than what I saw. Comparing the Bing to the National Agriculture Imagery Program shows the largest differences in tidal heights. Would it make sense to pull the coastline inland to match the highest image set, and extend the sand seaward to match the lowest tide?

ezekielf · 2024-06-21T12:33:05.958Z

Yes it definitely sounds like the coastline should be adjusted here. In fact it should be positioned at the average high tide line. See Tag:natural=coastline - OpenStreetMap Wiki

sbre · 2024-06-24T07:50:27.134Z

Mean of the high water springs only excludes a handful of tides every year, so generally it’s very safe to place the coastline at least as high as water visible in imagery. If you are unlucky enough that the imagery was captured in the few hours of the year the tide goes over, it’s generally just a foot or so most places. Hardly noticable given the often much lower precision of coastline in OSM.

Coastline in OpenStreetMap is more often too low than too high, if one looks at the actual definition