GRASS GIS 7 just got better: When reprojecting vector data, now automated vertex densification is applied. This reduces the reprojection error for long lines (or polygon boundaries). The needed improvement has been kindly added in v.proj by Markus Metz.
As an (extreme?) example, we generate a box in LatLong/WGS84 (EPSG: 4326) which is of 10 degree side length (see below for screenshot and at bottom for SHAPE file download of this “box” map):
[neteler@oboe ~]$ grass70 ~/grassdata/latlong/grass7/
# for the ease of generating the box, set computational region:
g.region n=60 s=40 w=0 e=30 res=10 -p
projection: 3 (Latitude-Longitude)
# generate the box according to current computational region:
Next we start GRASS GIS in a metric projection, here the EU LAEA:
Most comand line options for GDAL/OGR tools that accept a coordinate system will allow you to give the name of a file containing WKT. And if you prefix the filename with ESRI:: the library will interprete the WKT as being ESRI WKT and convert to “standard” format accordingly. The -s_srs switch is assigning a source coordinate system to your input data (in case it didn’t have this properly defined already), and the -t_srs is defining a target coordinate system to reproject to.
TIGER files in OGR
# linear features:
ogr2ogr tiger_lines.shp tgr46081.rt1 CompleteChain
# area features:
tigerpoly.py tgr46081.rt1 tiger_area.shp
OGR CSV driver: easily indicate column types
You can now write a little csv help file to indicate the columns types to OGR. It works as follows. Suppose you have a foobar.csv file that looks like this: