[Imports] Formal announcement of the import from LINZ

[Christoph Hormann]

On Monday 25 October 2021, Mateusz Konieczny via Imports wrote:
>
> Specifically, creevasse import in Antarctic was a mistake and should
> be reverted.

To be clear:  In my eyes there is nothing particularly wrong or bad with 
the LINZ crevasse data.  The problems with the crevasses are indicative 
of some of the underlying issues with the way this import was done 
(ignoring in particular the geometric incompatibilities with existing 
data) but these also occur with other features and just removing the 
crevasses again will not solve those.

The main problem with the LINZ crevasse data per se would be that it is 
based on a very wide concept of what constitutes a crevasse.  
Traditionally (and in OSM) a crevasse is a mechanical stress induced 
fracture in glacier ice.  In the LINZ data it seems to be also used for 
mapping penitente like structures resulting from differentiated 
ablation of the ice due to sunlight and sublimation/melting processes.

See for example on the Canada Glacier:

https://data.pgc.umn.edu/aerial/usgs/tma/photos/prev/CA0359/CA035931L/CA035931L0083_preview.jpg
https://data.pgc.umn.edu/aerial/usgs/tma/photos/prev/CA2373/CA237332V/CA237332V0041_preview.jpg
https://data.pgc.umn.edu/aerial/usgs/tma/photos/prev/CA3082/CA308200V/CA308200V0100_preview.jpg

More obvious flaws with non-crevasse features can be seen for example 
here:

https://www.openstreetmap.org/#map=12/-77.7395/163.1329&layers=D

As indicated before i suggest to separate imports of data in New Zealand 
from imports in the Antarctic.  And obviously to discuss plans before 
actually running imports.

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