[OSM-talk] Correcting coastlines

[J.D. Schmidt]

OJW skrev:
> There was a discussion on IRC about whether to upload PGS coastline 
> data "as-is", or to try and correct the 10-30m shift that it appears to have 
> relative to some other datasets.
> 
> http://wiki.openstreetmap.org/index.php/PGS_errata
> 
> Any views on this?  Shifting the data will require us to justify how we 
> calculated the error (e.g. several of the screenshots people have given me 
> seem to be from google maps) and preferably we need a model for the error 
> which is consistant worldwide.
> 
> Regards
> 
> OJW
> 
> p.s. how's Sydney harbour correlating with other data? 
> 
> p.p.s. did anyone email NGA to ask?

The Digital Globe Sat imagery from Googlemaps on the screendumps I
posted for Copenhagen, has only been used to visualize the shift to show
it to others.. The actual shift was calculated from the municipality
geodata available from the KMS portal.

I downloaded the Sydney area, and made a gpx track from the coastline
running from the Sydney Opera house and through three coves and inlets
to the east, and plotted it on the Digital Globe imagery. Looks like
it's shifted about 1 arcsecond north to the actual coastline. No E-W
shift. But I have no actual geodata to verify the shift against, only
the Digital Globe imagery from Googlemaps.

J.D."Dutch" Schmidt