mbloch / mapshaper-proj Goto Github PK

So I was about to post an issue on mapshaper to ask if this kind of project existed as part of your library and it does, woot!

So, would you mind saving me a little time and headache and explaining the easiest way to convert from UTM 18N, which is EPSG:26918, to latitude/longitude using your library's functions?

I've written my entire application on top of a port of mapshaper.org (I know, what a steal), so imagine that I've basically exported the model, map, and nav objects and have access to (most) of their functions. What would be the point of entry to pass in UTM coordinates to produce lat/lon coordinates?

Thanks for your time and awesomeness!

Paulana

QGIS and gdal seem to support Proj.4 projections that are not part of standard WKT by adding an extension attribute, like this: EXTENSION["PROJ4","+proj=eqearth +datum=WGS84 +wktext"].

We should do the same, even though ArcGIS and most other GIS applications will not be able to interpret this kind of .prj file.

The messages ported from Proj.4 can be confusing or wrong. Some examples:

$ echo 0 0 | mproj +init=epsg::3395
projection initialization failure
cause: no colon in init= string

$ echo 0 0 | mproj +init=eeee:3395
projection initialization failure
cause: no options found in 'init' file

I just released v0.17, which includes the the Equal Earth projection using the Proj.4 name "eqearth".

The mapshaper-proj source file is here

Original Java source file is here

(@berniejenny, I copied the comment block from your source code to comply with the Apache license that you're using, please let me know if there's a problem with the way I'm citing your work).

Link to journal article is here

+proj=eqearth is already available in Mapshaper, here is a screenshot comparing Equal Earth to Robinson:

This will allow high-quality NAD27 to NAD83 conversion using the command line version of mapshaper.

There have been ~200 commits to the Proj.4 repo since I ported mapshaper-proj

(Currently only lowercase works)

First, thanks for such a fantastic resource. Mapshaper is truly impressive!

I'm wondering if you've considered adding support for some of the other D3 composite projections that are based on albersusa?

https://geoexamples.com/d3-composite-projections/
https://www.npmjs.com/package/geo-albers-usa-territories

Would be great to use this projections with mapshaper.
Information about both versions in proj website :

• https://proj.org/operations/projections/igh.html
• https://proj.org/operations/projections/igh_o.html
  Proj code :
• https://github.com/OSGeo/PROJ/blob/master/src/projections/igh.cpp
• https://github.com/OSGeo/PROJ/blob/master/src/projections/igh_o.cpp

Recent improvement in mapshaper (antimeridian and circular clipping) are really great but maybe this kind of projection involve a different way of clipping.

Shouldn't throw an error for this kind of definition:

# Popular Visualisation CRS / Mercator (deprecated)
<3785> +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs <>

Useful for saving to Shapefile after reprojecting.