[Imports] Import of coastlines for Greenland

Christoph Hormann chris_hormann at gmx.de
Tue Jul 28 19:10:12 UTC 2015


First of all the license situation of GIMP is somewhat unclear, OSM does 
not qualify as academic purpose and it is not clear if the citation OSM 
can provide on the contributors page on the wiki is sufficient - so you 
would need explicit permission.

The current situation of the Greenland coastline in OSM en large (with 
the exception of some local mapping in smaller areas) is the following:

- west coast is mostly PGS based
- east coast is mostly GADM based
- north coast is based on MODIS imagery, partly improved by Landsat in 
the far north.

The GIMP land ocean mask is higher resolution than most of the current 
data in OSM but of varying quality.  You'd have to deal with a number 
of problems:

- wrong classification due to shadows and wet snow. 
- positional accuracy problems due to bad alignment of Landsat images 
used.
- outdated ice coastlines due to 15 year old data basis

Examples showing this (from East Greenland as magenta mask in comparison 
to up-to-date Landsat imagery and the OSM coastline (blue line)):

http://www.imagico.de/files/coastline_greenland1.png
http://www.imagico.de/files/coastline_greenland2.png

So to get actual improvements out of this compared to current data you'd 
need to manually fix a lot of problems and would still end up with data 
significantly worse than what you could produce from available imagery 
by hand (or where water is ice free in summer with semi-automated 
mapping).

By the way if you have contacts to Greenland mapping authorities getting 
data and permission to use for names of islands, mountains, fjords, 
bays etc. would be most valuable.  For a mapper working in essentially 
unpopulated areas like northern and eastern Greenland such are 
difficult to determine reliably.

-- 
Christoph Hormann
http://www.imagico.de/



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