[GRASS-user] units used in r.stream.distance

GRASS GRASS user
1

Hi,

what are the units used to calculate distance with r.stream.distance in geographic (latlon) locations?

Thanks,

madi

···

Best regards,

Dr. Margherita DI LEO
Scientific / technical project officer

European Commission - DG JRC
Institute for Environment and Sustainability (IES)
Via Fermi, 2749
I-21027 Ispra (VA) - Italy - TP 261

Tel. +39 0332 78 3600
margherita.di-leo@jrc.ec.europa.eu

Disclaimer: The views expressed are purely those of the writer and may not in any circumstance be regarded as stating an official position of the European Commission.

2

On Dec 16, 2014, at 9:20 AM, Margherita Di Leo <diregola@gmail.com> wrote:

what are the units used to calculate distance with r.stream.distance in geographic (latlon) locations?

As far as I know, latlon locations use latlon for the unit of measurement as well.

Note that you can inspect what units you are using by opening up the PROJ_UNITS located inside the GRASS location, or display them with “g.region -p"

Best,

Jeshua Lacock
Founder/Engineer
3DTOPO Incorporated
<http://3DTOPO.com>
Phone: 208.462.4171

3

On Tue, Dec 16, 2014 at 8:35 PM, Jeshua Lacock <jeshua@3dtopo.com> wrote:

On Dec 16, 2014, at 9:20 AM, Margherita Di Leo <diregola@gmail.com> wrote:

what are the units used to calculate distance with r.stream.distance in geographic (latlon) locations?

As far as I know, latlon locations use latlon for the unit of measurement as well.

No it depends on the respective command. Eg:

http://grass.osgeo.org/grass70/manuals/v.distance.html#notes
"In lat-long locations v.distance gives distances (dist, from_along,
and to_along) not in degrees but in meters calculated as geodesic
distances on a sphere. "

Regarding r.stream.distance one would need to check the source code
(and then document it).

Markus

4

Hi,

···

On Tue, Dec 16, 2014 at 9:09 PM, Markus Neteler <neteler@osgeo.org> wrote:

No it depends on the respective command. Eg:

http://grass.osgeo.org/grass70/manuals/v.distance.html#notes
"In lat-long locations v.distance gives distances (dist, from_along,
and to_along) not in degrees but in meters calculated as geodesic
distances on a sphere. "

Regarding r.stream.distance one would need to check the source code
(and then document it).

Thank you. Jarek (the author of the module) confirmed that the distance is in meters. I’m expanding the documentation accordingly,

Thanks,

madi

–

Best regards,

Dr. Margherita DI LEO
Scientific / technical project officer

European Commission - DG JRC
Institute for Environment and Sustainability (IES)
Via Fermi, 2749
I-21027 Ispra (VA) - Italy - TP 261

Tel. +39 0332 78 3600
margherita.di-leo@jrc.ec.europa.eu

Disclaimer: The views expressed are purely those of the writer and may not in any circumstance be regarded as stating an official position of the European Commission.