[GRASS-user] Incorrect re-projection from EPSG:4326 to 3857

[Markus Neteler]

On Thu, Jan 4, 2018 at 6:25 PM, Markus Metz
<markus.metz.giswork at gmail.com> wrote:
> On Thu, Jan 4, 2018 at 9:08 AM, Helmut Kudrnovsky <hellik at web.de> wrote:
>>
>> Zhiyu (Drew) Li wrote
>> > Hi there,
>> >
>> > I was trying to re-project a EPSG:4326 coordinate into EPSG:3857 using
>> > GRASS, but I found GDAL gave me a different result.
>> >
>> > GRASS (7.2.2):
...
> Regarding EPSG:3857:
> Uses spherical development of ellipsoidal coordinates. Relative to WGS 84 /
> World Mercator (CRS code 3395) errors of 0.7 percent in scale and
> differences in northing of up to 43km in the map (equivalent to 21km on the
> ground) may arise.
>
> This has been fixed in recent GRASS 7.4 and GRASS 7.5, providing same
> results like GDAL.

I have added a related note here for the upcoming 7.4.0 release:

https://trac.osgeo.org/grass/wiki/Release/7.4.0-News#Projectionsupport

markusN