ll2xy vs latlon2statgrid and xy2ll vs statgrid2latlon
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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)
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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 which is packaged with a whole bunch of useful tools (have a look at included binaries)
Cropping coordinates (station locations) using GMT
Option 1: using gmt select
gmt select -Fpolygon.ll hh400.ll > hh400_land.ll
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gmt select -F/nesi/projects/nesi00213/PlottingData/Paths/lds-nz-coastlines-and-islands/150k.gmt non-uniform-100m.ll > non-uniform-land.ll
Option 2: using gmt spatial
Convert points to virtual paths by duplicating position and naming segment with 3rd value (station name).
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awk '{if ($1 == ">") n=$2; if (NR % 3 == 2) print $1, $2, n}' hh400_cropped.ll > hh400_land.ll...