[GRASS-user] scale error for each pixel

[Markus Neteler]

Dear Ken,

On Thu, Nov 9, 2017 at 12:30 PM, Ken Mankoff <mankoff at gmail.com> wrote:
> On 2017-11-02 at 07:17, Helmut Kudrnovsky <hellik at web.de> wrote:
>> Ken Mankoff wrote
>>> Does GRASS (or GDAL?, proj4?) have a function (or addon) to provide the
>>> scale error  for a given cell?
>>>
>>> My understanding is that for a given projection, the "lat_ts" term of
>>> the proj4 string describing the projection is where 1 m in GRASS is
>>> actually 1 m. Elsewhere, errors grow. I'd like to track these.
>>
>> AFAIR there is now an area function in r.mapcalc in GRASS trunk to
>> calculate the pixel area.
>
> Is the scale error only in longitude and never in latitude? Or can it be in both?
> Is there a way to find the error for a length error rather than an area error?
> Specifically, for a vector line with an arbitrary heading?

This is probably a question for the PROJ mailing list?

Markus