[GRASS-user] scale error for each pixel

[Ken Mankoff]

Dear Helmut and GRASS List,

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?

Thanks,

  -k.