path: root/man/man1/geod.1

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.TH "GEOD" "1" "Mar 18, 2018" "5.0.0" "PROJ.4"
.SH NAME
geod \- Geodesic computations
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.SH SYNOPSIS
.INDENT 0.0
.INDENT 3.5
\fBgeod\fP \fI+ellps=<ellipse>\fP [ \fB\-afFIlptwW\fP [ args ] ] [ \fI+args\fP ] file[s]
.sp
\fBinvgeod\fP \fI+ellps=<ellipse>\fP [ \fB\-afFIlptwW\fP [ args  ]  ]  [ \fI+args\fP  ] file[s]
.UNINDENT
.UNINDENT
.SH DESCRIPTION
.sp
\fBgeod\fP  (direct)  and  \fBinvgeod\fP (inverse) perform geodesic
(Great Circle) computations for determining latitude,  longitude  and back
azimuth  of  a terminus point given a initial point latitude, longitude,
azimuth and distance (direct) or  the  forward and  back azimuths and distance
between an initial and terminus point latitudes and  longitudes  (inverse).
The  results  are accurate  to  round  off for |f| < 1/50, where
f is flattening.
.sp
\fBinvgeod\fP may not be available on all  platforms;  in  this  case
use \fI\%geod \-I\fP instead.
.sp
The following command\-line options can appear in any order:
.INDENT 0.0
.TP
.B \-I
Specifies that the inverse geodesic computation is to be performed. May be
used with execution of geod as an alternative to invgeod execution.
.UNINDENT
.INDENT 0.0
.TP
.B \-a
Latitude and longitudes of the initial and terminal points, forward and
back azimuths and distance are  output.
.UNINDENT
.INDENT 0.0
.TP
.B \-ta
A specifies a character employed as the first character to denote a control
line to be passed through without processing.
.UNINDENT
.INDENT 0.0
.TP
.B \-le
Gives a listing of all the ellipsoids that may be selected with the
\fI+ellps=\fP option.
.UNINDENT
.INDENT 0.0
.TP
.B \-lu
Gives a listing of all the units that  may  be  selected with the \fI+units=\fP
option.
.UNINDENT
.INDENT 0.0
.TP
.B \-f <format>
Format is a printf format string to control the output form of the
geographic coordinate values. The default mode is DMS for geographic
coordinates and “%.3f” for distance.
.UNINDENT
.INDENT 0.0
.TP
.B \-F <format>
Format is a printf format string to control the output form of the distance
value (\fB\-F\fP). The default mode is DMS for geographic coordinates and
“%.3f” for distance.
.UNINDENT
.INDENT 0.0
.TP
.B \-w<n>
N is the number of significant fractional digits to employ for seconds
output (when the option is not specified, \fB\-w3\fP is assumed).
.UNINDENT
.INDENT 0.0
.TP
.B \-W<n>
N is the number of significant fractional digits to employ for seconds
output. When \fB\-W\fP is employed the fields will be constant width
with leading zeroes.
.UNINDENT
.INDENT 0.0
.TP
.B \-p
This option causes the azimuthal values to be output as unsigned DMS
numbers between 0 and 360 degrees. Also note \fI\%\-f\fP\&.
.UNINDENT
.sp
The  \fI+args\fP  command\-line  options  are associated with geodetic
parameters for specifying the ellipsoidal  or  sphere  to  use.
controls.  The options are processed in  left  to  right  order
from  the  command  line.  Reentry of an option is ignored with
the first occurrence assumed to be the desired value.
.sp
See the PROJ documentation for a full list of these parameters and
controls.
.sp
One or more files (processed in left to  right  order)  specify
the  source  of  data  to be transformed.  A \fB\-\fP will specify the
location of processing standard input.  If no files are  specified,
the input is assumed to be from stdin.
.sp
For  direct determinations input data must be in latitude, longitude,
azimuth and distance order and output will be latitude,
longitude  and  back  azimuth of the terminus point.  Latitude,
longitude of the initial and terminus point are input  for  the
inverse  mode  and respective forward and back azimuth from the
initial and terminus points are output along with the  distance
between the points.
.sp
Input  geographic  coordinates  (latitude  and  longitude)  and
azimuthal data must be in decimal degrees  or  DMS  format  and
input distance data must be in units consistent with the ellipsoid
major axis or sphere radius units.  The latitude must  lie
in the range [\-90d,90d].  Output geographic coordinates will be
in DMS (if the \fI\%\-f\fP switch is not employed) to 0.001” with trailing,
zero\-valued minute\-second fields deleted.  Output distance
data will be in the same  units  as  the  ellipsoid  or  sphere
radius.
.sp
The Earth’s ellipsoidal figure may be selected in the same manner
as program \fBproj\fP by using \fI+ellps=\fP, \fI+a=\fP, \fI+es=\fP, etc.
.sp
Geod may also be used to determine  intermediate  points  along
either  a  geodesic  line between two points or along an arc of
specified distance from a geographic point.  In both  cases  an
initial  point must be specified with \fI+lat_1=lat\fP and \fI+lon_1=lon\fP
parameters  and  either  a  terminus   point   \fI+lat_2=lat\fP   and
\fI+lon_2=lon\fP  or  a  distance  and azimuth from the initial point
with \fI+S=distance\fP and \fI+A=azimuth\fP must be specified.
.sp
If points along a geodesic are to  be  determined  then  either
\fI+n_S=integer\fP  specifying  the  number  of  intermediate  points
and/or  \fI+del_S=distance\fP  specifying  the  incremental  distance
between points must be specified.
.sp
To  determine  points along an arc equidistant from the initial
point both \fI+del_A=angle\fP  and  \fI+n_A=integer\fP  must  be  specified
which determine the respective angular increments and number of
points to be determined.
.SH EXAMPLES
.sp
The following script determines the geodesic azimuths and  distance in U.S.
statute miles from Boston, MA, to Portland, OR:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
geod +ellps=clrk66 <<EOF \-I +units=us\-mi
42d15\(aqN 71d07\(aqW 45d31\(aqN 123d41\(aqW
EOF
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
which gives the results:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
\-66d31\(aq50.141" 75d39\(aq13.083" 2587.504
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
where the first two values are the azimuth from Boston to Portland,
the back azimuth from Portland to Boston followed by the distance.
.sp
An  example  of forward geodesic use is to use the Boston location
and determine Portland’s location by azimuth and distance:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
geod +ellps=clrk66 <<EOF +units=us\-mi
42d15\(aqN 71d07\(aqW \-66d31\(aq50.141" 2587.504
EOF
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
which gives:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
45d31\(aq0.003"N 123d40\(aq59.985"W 75d39\(aq13.094"
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
\fBNOTE:\fP
.INDENT 0.0
.INDENT 3.5
Lack  of precision in the distance value compromises the
precision of the Portland location.
.UNINDENT
.UNINDENT
.SH FURTHER READING
.INDENT 0.0
.IP 1. 3
\fI\%GeographicLib\fP\&.
.IP 2. 3
C. F. F. Karney, \fI\%Algorithms for Geodesics\fP, J. Geodesy \fB87\fP(1), 43–55 (2013);
\fI\%addenda\fP\&.
.IP 3. 3
\fI\%A geodesic bibliography\fP\&.
.UNINDENT
.SH SEE ALSO
.sp
\fBproj(1)\fP, \fBcs2cs(1)\fP, \fBcct(1)\fP, \fBgeod(1)\fP, \fBgie(1)\fP
.SH BUGS
.sp
A list of know bugs can be found at \fI\%http://github.com/OSGeo/proj.4/issues\fP
where new bug reports can be submitted to.
.SH HOME PAGE
.sp
\fI\%http://proj4.org/\fP
.SH AUTHOR
Charles Karney
.SH COPYRIGHT
1983-2018
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