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Interpolation/

map_npoints.pro

Return the distance in meter between all np0 points P0 and all np1 points P1 on a sphere. If keyword /TWO_BY_TWO is given then returns the distances between number n of P0 points and number n of P1 points (in that case, np0 and np1 must be equal). Same as MAP_2POINTS with the meter parameter but for n points without do loop.

map_npoints Maps

result = map_npoints(lon0, lat0, lon1, lat1, AZIMUTH=AZIMUTH, RADIANS=RADIANS, RADIUS=RADIUS, MIDDLE=MIDDLE, TWO_BY_TWO=TWO_BY_TWO)

Return value

An (np0,np1) array giving the distance in meter between np0 points P0 and np1 points P1. Element (i,j) of the output is the distance between element P0[i] and P1[j]. If keyword /TWO_BY_TWO is given then map_npoints returns an np-elements vector giving the distance in meter between P0[i] and P1[i] (in that case, we have np0 = np1 = np) ; if /MIDDLE see this keyword.

Parameters

lon0 in required

lat0 in required

np0 elements vector. longitudes and latitudes of np0 points P0

lon1 in required

lat1 in required

np1 elements vector. longitude and latitude of np1 points P1

Keywords

AZIMUTH

A named variable that will receive the azimuth of the great circle connecting the two points, P0 to P1

RADIANS

if set, inputs and angular outputs are in radians, otherwise degrees.

RADIUS default: 6378206.4d0

If given, return the distance between the two points calculated using the given radius. Default value is the Earth radius.

MIDDLE

to get the longitude/latitude of the middle point between P0 and P1.

TWO_BY_TWO

If given, then map_npoints returns the distances between number n of P0 points and number n of P1 pointsi. In that case, np0 and np1 must be equal.

Examples

 IDL> print, $
 IDL> map_npoints([-105.15,1],[40.02,1],[-0.07,100,50],[51.30,20,0])
 7551369.3 5600334.8
 12864354. 10921254.
 14919237. 5455558.8

 IDL> lon0 = [-10, 20, 100]
 IDL> lat0 = [0, -10, 45]
 IDL> lon1 = [10, 60, 280]
 IDL> lat1 = [0, 10, 45]
 IDL> dist = map_npoints(lon0, lat0, lon1, lat1, AZIMUTH = azi)
 IDL> help, dist, azi
 DIST DOUBLE = Array[3, 3]
 AZI DOUBLE = Array[3, 3]
 IDL> print, dist[4*lindgen(3)], azi[4*lindgen(3)]
 2226414.0 4957944.5 10018863.
 90.000000 64.494450 4.9615627e-15
 IDL> dist = map_npoints(lon0, lat0, lon1, lat1, AZIMUTH = azi, /TWO_BY_TWO)
 IDL> help, dist, azi
 DIST DOUBLE = Array[3]
 AZI DOUBLE = Array[3]
 IDL> print, dist, azi
 2226414.0 4957944.5 10018863.
 90.000000 64.494450 4.9615627e-15
 IDL> print, map_2points(lon0[0], lat0[0], lon1[0], lat1[0])
 20.000000 90.000000
 IDL> print, map_npoints(lon0[0], lat0[0], lon1[0], lat1[0], AZIMUTH=azi)/6378206.4d0 / !dtor, azi
 20.000000
 90.000000

 IDL> lon0 = [-10, 20, 100]
 IDL> lat0 = [0, -10, 45]
 IDL> lon1 = [10, 60, 280]
 IDL> lat1 = [0, 10, 45]
 IDL> mid = map_npoints(lon0, lat0, lon1, lat1, /MIDDLE, /TWO_BY_TWO)
 IDL> print, reform(mid[0,*]), reform(mid[1,*])
 0.0000000 40.000000 190.00000
 0.0000000 -1.5902773e-15 90.000000
 IDL> print, (map_2points(lon0[0], lat0[0], lon1[0], lat1[0], npath = 3))[*, 1]
 0.0000000 0.0000000
 IDL> print, (map_2points(lon0[1], lat0[1], lon1[1], lat1[1], npath = 3))[*, 1]
 40.000000 -1.5902773e-15
 IDL> print, (map_2points(lon0[2], lat0[2], lon1[2], lat1[2], npath = 3))[*, 1]
 190.00000 90.000000

Version history

Version

$Id: map_npoints.pro 327 2007-12-13 16:22:35Z pinsard $

History

Based on the IDL function map_2points.pro,v 1.6 2001/01/15 Sebastien Masson (smasson@lodyc.jussieu.fr) October 2003

Produced by IDLdoc 2.0.