[GRASS-dev] v.proj: line densification added for reprojection error minimization

Markus Neteler neteler at osgeo.org
Sat Dec 13 15:43:01 PST 2014


Markus Metz kindly added line densification to  v.proj (r63307)

[neteler at oboe ~]$ grass70 ~/grassdata/latlong/grass7/

g.region n=60 s=40 w=0 e=30 res=10 -p
projection: 3 (Latitude-Longitude)
zone:       0
datum:      wgs84
ellipsoid:  wgs84
north:      60N
south:      40N
west:       0
east:       30E
nsres:      10
ewres:      10
rows:       2
cols:       3
cells:      6

v.in.region box_latlong_10deg

# EPSG 3035, metric EU LAEA:
grass70 ~/grassdata/europe_laea/user1/
GRASS 7.0.0svn (europe_laea): >

# "traditional way"
v.proj box_latlong_10deg out=box_latlong_10deg_no_densification
location=latlong mapset=grass7 smax=0

# with new line densification
v.proj box_latlong_10deg out=box_latlong_10deg_yes_densification
location=latlong mapset=grass7

g.region vect=box_latlong_10deg_no_densification

# compare:
d.mon wx0
d.vect box_latlong_10deg_no_densification color=red
d.vect box_latlong_10deg_yes_densification color=green fill_color=none

The result (see screenshot, maybe an extreme example but yet helpful
to show the improvement) shows how nicely the projection is performed
now (green color is new output).
Please benchmark this with other GIS...

Thank to Markus Metz for this implementation. I took liberty to
backport it to relbranch70 in r63532.

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