Re: distance on the equator by map project

On Mar 13, 2014, at 11:19 AM, Namba Takaya <[email protected]> wrote:

> Dear Sir
Careful, the female GMT users would think badly of you.

> 
> I tried to calculate the distance on the equator to check the result of mapproject as
> 
>  lon=2
>  lat=0
>  lonn=3
>  latn=0
>  echo $lon $lat |mapproject -f0x,1y -G$lonn/$latn/n 
> 
> and the result is
> 2       0       60.0405398135.
> 
> My question is why it is not 60.0000 nautical miles exactly?
> 
Think that is only true for a sphere.  A nautical mile is defined to be 1852 meters, not 1 minute of arc.

But I see
echo 0 0 | mapproject -G1/0/n --PROJ_ELLIPSOID=Sphere
0	0	60.0405398134
which seems wrong, so we will have to have a look.
-p

> regards,
> 
> takaya
> 
> 

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