#About
We need to generate a graticule that will project cleanly (with smooth arcs) at world scale. The graticule should have a dense distribution of internal nodes along it's line, especially along the ±180, ±90 WGS84 bounding box.
Uses pygraticule (embedded here) by Alex Mandel with modifications by Nathaniel Vaughn KELSO.
#Usage
The included Makefile should be run as:
make clean
followed by
make all
Behind the scenes, it's running commands like:
python pygraticule.py -g 1 -o outfile.geojson
Once the GeoJSON versions are created, the Makefile uses OGR/GDAL (assumes that's installed) to convert to SHP format and then package up into ZIP folders.
Examples
When we project out of WGS84 to another coordinate system that is not cylindrical, we need to have enough intermediate nodes on the paths so the GIS application shows a "curve". Most GIS do not auto-densify stright lines during the projection so we need to add these extra nodes in the raw geodata.
Here we see Robinson using enough nodes:
Box results when nodes are sparse:
The two superimposed:
The proj4 string for Robinson is:
+proj=robin +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs