作者: 冉维 时间: 2016-1-23 23:04
不是计信院院的不懂。。。 作者: madio 时间: 2016-1-24 16:12
莫非是要定义一个距离函数吗？欧式距离？ 作者: 远行的小船儿666 时间: 2016-1-24 20:33
distance Distance between points on sphere or ellipsoid
[ARCLEN, AZ] = distance(LAT1,LON1,LAT2,LON2) computes the lengths,
ARCLEN, of the great circle arcs connecting pairs of points on the
surface of a sphere. In each case, the shorter (minor) arc is assumed.
The function can also compute the azimuths, AZ, of the second point in
each pair with respect to the first (that is, the angle at which the
arc crosses the meridian containing the first point). The input
latitudes and longitudes, LAT1, LON1, LAT2, LON2, can be scalars or
arrays of equal size and must be expressed in degrees. ARCLEN is
expressed in degrees of arc and will have the same size as the input
arrays. AZ is measured clockwise from north, in units of degrees.
When given a combination of scalar and array inputs, the scalar inputs
are automatically expanded to match the size of the arrays.
[ARCLEN, AZ] = distance(LAT1,LON1,LAT2,LON2,ELLIPSOID) computes
geodesic arc length and azimuth assuming that the points lie on the
reference ellipsoid defined by the input ELLIPSOID. ELLIPSOID is a
reference ellipsoid (oblate spheroid) object, a reference sphere
object, or a vector of the form [semimajor_axis, eccentricity]. The
output, ARCLEN, is expressed in the same length units as the semimajor
axis of the ellipsoid.
[ARCLEN, AZ] = distance(LAT1,LON1,LAT2,LON2,UNITS) uses the input
string UNITS to define the angle unit of the outputs ARCLEN and AZ and
the input latitude-longitude coordinates. UNITS may equal 'degrees'
(the default value) or 'radians'.
[ARCLEN, AZ] = distance(LAT1,LON1,LAT2,LON2,ELLIPSOID,UNITS) uses the
UNITS string to specify the units of the latitude-longitude
coordinates, but the output range has the same units as the
semimajor axis of the ellipsoid.
[ARCLEN, AZ] = distance(TRACK,...) uses the input string TRACK to
specify either a great circle/geodesic or a rhumb line arc. If TRACK
equals 'gc' (the default value), then great circle distances are
computed on a sphere and geodesic distances are computed on an
ellipsoid. If TRACK equals 'rh', then rhumb line distances are computed
on either a sphere or ellipsoid.
[ARCLEN, AZ] = distance(PT1,PT2) accepts N-by-2 coordinate arrays
PT1 and PT2 such that PT1 = [LAT1 LON1] and PT2 = [LAT2 LON2] where
LAT1, LON1, LAT2, and LON2 are column vectors. It is equivalent to
ARCLEN = distance(PT1(:,1),PT1(:,2),PT2(:,1),PT2(:,2)).
[ARCLEN, AZ] = distance(PT1,PT2,ELLIPSOID)
[ARCLEN, AZ] = distance(PT1,PT2,UNITS),
[ARCLEN, AZ] = distance(PT1,PT2,ELLIPSOID,UNITS) and
[ARCLEN, AZ] = distance(TRACK,PT1,...) are all valid calling forms.
Remark on Computing Azimuths
----------------------------
Note that when both distance and azimuth are required for the same
point pair(s), it's more efficient to compute both with a single
call to distance. That is, use:
[ARCLEN, AZ] = distance(...);
rather than its slower equivalent:
ARCLEN = distance(...);
AZ = AZIMUTH(...);
Remark on Output Units
----------------------
To express the output ARCLEN as an arc length expressed in either
degrees or radians, omit the ELLIPSOID argument. This is possible only
on a sphere. If ELLIPSOID is supplied, ARCLEN is expressed in the same
length units as the semimajor axis of the ellipsoid. Specify ELLIPSOID
as [R 0] to compute ARCLEN as a distance on a sphere of radius R, with
ARCLEN having the same units as R.
Remark on Eccentricity
----------------------
Geodesic distances on an ellipsoid are valid only for small
eccentricities typical of the Earth (e.g., 0.08 or less).
Remark on Long Geodesics
------------------------
Distance calculations for geodesics degrade slowly with increasing
distance and may break down for points that are nearly antipodal,
and/or when both points are very close to the Equator. In addition,
for calculations on an ellipsoid, there is a small but finite input
space, consisting of pairs in which both the points are nearly
antipodal AND both points fall close to (but not precisely on) the
Equator. In this case, a warning is issued and both ARCLEN and AZ
are set to NaN for the "problem pairs."
See also azimuth, reckon.
Reference page in Help browser
doc distance
作者: 远行的小船儿666 时间: 2016-1-24 20:33
大概是这样纸吧 作者: 远行的小船儿666 时间: 2016-1-24 20:34
distance Distance between points on sphere or ellipsoid
[ARCLEN, AZ] = distance(LAT1,LON1,LAT2,LON2) computes the lengths,
ARCLEN, of the great circle arcs connecting pairs of points on the
surface of a sphere. In each case, the shorter (minor) arc is assumed.
The function can also compute the azimuths, AZ, of the second point in
each pair with respect to the first (that is, the angle at which the
arc crosses the meridian containing the first point). The input
latitudes and longitudes, LAT1, LON1, LAT2, LON2, can be scalars or
arrays of equal size and must be expressed in degrees. ARCLEN is
expressed in degrees of arc and will have the same size as the input
arrays. AZ is measured clockwise from north, in units of degrees.
When given a combination of scalar and array inputs, the scalar inputs
are automatically expanded to match the size of the arrays.
[ARCLEN, AZ] = distance(LAT1,LON1,LAT2,LON2,ELLIPSOID) computes
geodesic arc length and azimuth assuming that the points lie on the
reference ellipsoid defined by the input ELLIPSOID. ELLIPSOID is a
reference ellipsoid (oblate spheroid) object, a reference sphere
object, or a vector of the form [semimajor_axis, eccentricity]. The
output, ARCLEN, is expressed in the same length units as the semimajor
axis of the ellipsoid.
[ARCLEN, AZ] = distance(LAT1,LON1,LAT2,LON2,UNITS) uses the input
string UNITS to define the angle unit of the outputs ARCLEN and AZ and
the input latitude-longitude coordinates. UNITS may equal 'degrees'
(the default value) or 'radians'.
[ARCLEN, AZ] = distance(LAT1,LON1,LAT2,LON2,ELLIPSOID,UNITS) uses the
UNITS string to specify the units of the latitude-longitude
coordinates, but the output range has the same units as the
semimajor axis of the ellipsoid.
[ARCLEN, AZ] = distance(TRACK,...) uses the input string TRACK to
specify either a great circle/geodesic or a rhumb line arc. If TRACK
equals 'gc' (the default value), then great circle distances are
computed on a sphere and geodesic distances are computed on an
ellipsoid. If TRACK equals 'rh', then rhumb line distances are computed
on either a sphere or ellipsoid.
[ARCLEN, AZ] = distance(PT1,PT2) accepts N-by-2 coordinate arrays
PT1 and PT2 such that PT1 = [LAT1 LON1] and PT2 = [LAT2 LON2] where
LAT1, LON1, LAT2, and LON2 are column vectors. It is equivalent to
ARCLEN = distance(PT1(:,1),PT1(:,2),PT2(:,1),PT2(:,2)).
[ARCLEN, AZ] = distance(PT1,PT2,ELLIPSOID)
[ARCLEN, AZ] = distance(PT1,PT2,UNITS),
[ARCLEN, AZ] = distance(PT1,PT2,ELLIPSOID,UNITS) and
[ARCLEN, AZ] = distance(TRACK,PT1,...) are all valid calling forms.
Remark on Computing Azimuths
----------------------------
Note that when both distance and azimuth are required for the same
point pair(s), it's more efficient to compute both with a single
call to distance. That is, use:
[ARCLEN, AZ] = distance(...);
rather than its slower equivalent:
ARCLEN = distance(...);
AZ = AZIMUTH(...);
Remark on Output Units
----------------------
To express the output ARCLEN as an arc length expressed in either
degrees or radians, omit the ELLIPSOID argument. This is possible only
on a sphere. If ELLIPSOID is supplied, ARCLEN is expressed in the same
length units as the semimajor axis of the ellipsoid. Specify ELLIPSOID
as [R 0] to compute ARCLEN as a distance on a sphere of radius R, with
ARCLEN having the same units as R.
Remark on Eccentricity
----------------------
Geodesic distances on an ellipsoid are valid only for small
eccentricities typical of the Earth (e.g., 0.08 or less).
Remark on Long Geodesics
------------------------
Distance calculations for geodesics degrade slowly with increasing
distance and may break down for points that are nearly antipodal,
and/or when both points are very close to the Equator. In addition,
for calculations on an ellipsoid, there is a small but finite input
space, consisting of pairs in which both the points are nearly
antipodal AND both points fall close to (but not precisely on) the
Equator. In this case, a warning is issued and both ARCLEN and AZ
are set to NaN for the "problem pairs."
