ll2xy vs latlon2statgrid and xy2ll vs statgrid2latlon
Tools to convert between latitude, longitude and gridpoints/distance for a given simulation domain.
Common Properties
- Accept 2 (x, y) or 3 (x, y, station) values. The 3rd value is copied to output.
| ll2xy and xy2ll | latlon2statgrid and statgrid2latlon | Notes |
|---|---|---|
| can work on standard input or files | must work on files only | ll2xy more flexible, can use pipes instead of files |
| xy I/O is in km from centre | statgrid I/O is point position from top left corner | can convert between output styles given: horizontal spacing and total domain size |
| given model grid point ll coordinates, resulting x, y values are equidistant | incremental statgrid points converted to lat lon plotted: are not equidistant and are systematically shifted some points are out of place compared with neighbours | this is why ll2xy and xy2ll has a wrapper function to make sure converted points are equidistant given horizontal spacing or grid point increments. |
Conversion between geographic data formats
convert a shapefile from NZGD2000 (found on LINZ) to WGS84 (different source spacial reference system and output srs)
ogr2ogr -f "ESRI Shapefile" wgs84.shp linz.shp -s_srs EPSG:2193 -t_srs EPSG:4326 -lco ENCODING=UTF-8
convert a shapefile from NZGD2000 to GMT (generic mapping tools) format WGS84 (for use with tools like gmt psxy) (changing output format)
ogr2ogr -f "OGR_GMT" wgs84.gmt linz.shp -s_srs EPSG:2193 -t_srs EPSG:4326
NOTE: GMT (5.3) will not plot segments with missing headers gmt.soest.hawaii.edu/issues/1072 which results in missing segments. GRASS will output all headers when exporting OGR_GMT (v.out.ogr). Alternatively run a command like the following to remove all headers
grep -v '^#' wgs84.gmt > wgs84_nohead.gmt
EPSG:2193 is NZGD2000 http://spatialreference.org/ref/epsg/nzgd2000-new-zealand-transverse-mercator-2000/
EPSG:4326 is WGS84 http://spatialreference.org/ref/epsg/4326/
- ogr2ogr is part of GDAL