[PROJ] Correcting map projection errors

[Charles Karney]

On 4/24/19 10:58 PM, Ken Mankoff wrote:
> Hi Charles,
> 
> Thanks for contributing to the discussion. I'm going offline for the
> next 5 weeks and so I can't follow up much more on this, but I'm happy
> to hear you think the current method is probably good enough.

You should verify this!  Take a sampling of rectangles over your map and
compare the area computations:

* projected area with the scale correction,
* area returned by Planimeter,

and check that the discrepancy is small enough for your purposes.

> I'm not tied to proj4 or any specific tool, but prefer to use existing
> user-level tools rather than code my own, even a simple wrapper function
> - so for this reason I would rather run your planimeter tool than access
> the proj function you link to. Unless that function is exposed through
> the proj CLI interface somehow.

No, the proj CLI does not include area calculations.  The geod program
just solves plain the direct and inverse geodesic problems.