[GRASS-user] RE:How to find shortest distances from the investigation point to the shoreline

[Hamish]

sgw00412 wrote:
> I tested by two kinds of geographical coordinate systems by
> using the same data.
> 
> One of the geographical coordinate systems is UTM54, and
> the remainder is wgs84. 
> 
> data :point vector data (10 points) and a line vector data
> OS: grass 6.2.3 on Cygwin.
> 
> As a result, the case of UTM54 obtained the distance of meter.
> On the other hand, wgs84 obtained the distance of decimal value.
> 
> So, I guess that the decimal value of wgs84 is a degree of
> latitude longitude.
>  
> 
> Grass manual wrote that "...In lat-long locations v.distance gives
> distances (dist and to_along) in meters not in degrees calculated as
> geodesic distances on a sphere.."
> http://www.ces.iisc.ernet.in/grass/grass64/manuals/html64_user/v.distance.html
> 
> Though this manual is version 6.4, the manual of version
> 6.2 is not written it.
> 
> Is this interpretation correct?
> 
> If it is so, please teach me the method of converting the
> decimal value into the meter. 


Yes, version 6.2.3 is giving distances in (useless) degree units. This
was fixed in Jan 2008 by Martin to use geodesic distance in meters, so
GRASS 6.3.0 and the upcoming 6.4 do return meters. But 6.2.3 was
released in Nov 2007 and so is too old to have that fix.


Hamish