Re: [ferret_users]convert lat,lon in km

[James Orr <James.Orr@xxxxxx>]

Hi Xavier,

Attached is a simple script (distance.jnl) that I wrote to compute
distance (in km) between two points of different latitude and
longitude.  It uses the classical approach (spherical law of
cosines).  Other formulas such as the Haversine formula can also be
found at

  http://www.movable-type.co.uk/scripts/LatLong.html

Here is an example of using this distance script:

let lat1=0 ; let lon1=0
let lat2=90 ; let lon2=0
go distance
list dist

-- Jim


On Wed, 8 Feb 2006, Xavier Couvelard wrote:

> Hi,
> 
> Using samplexy, i obtain a new xaxis from 1 to 90, so i need to have 
> some meters to get a transport in m3/s.
> 
> How can i get the distance in meters from to points in lat lon coords?
> 
> Thanks
> Xavier
> 

-- 
======================================================================
   James Orr                      
   LSCE/IPSL, Laboratoire des Sciences du Climat et de l'Environnement
   CEA-CNRS-UVSQ

   LSCE/IPSL, CEA Saclay           http://www.ipsl.jussieu.fr/~jomce
   Bat. 712 - Orme                 mailto:  orr@cea.fr
   Point courrier 132
   F-91191 Gif-sur-Yvette Cedex    Phone:   (33) (0)1 69 08 77 23
   FRANCE                          Fax:     (33) (0)1 69 08 30 73
======================================================================
!See formulas on http://www.movable-type.co.uk/scripts/LatLong.html

! Distance formula from the spherical law of cosines

  let R = 6371         !Earth's mean radius 
  let pi = acos(-1)
  let deg2rad = pi/180 !Conversion factor to convert between degrees to radians
! Convert lons and lats from degrees to radians:
  let rlon1 = lon1 * deg2rad ; let rlon2 = lon2 * deg2rad
  let rlat1 = lat1 * deg2rad ; let rlat2 = lat2 * deg2rad

! let delrlat = rlat2 - rlat1
  let delrlon = rlon2 - rlon1
  let dist = acos(sin(rlat1) * sin(rlat2) + cos(rlat1) * cos(rlat2) * cos(delrlon)) * R