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.TH ROUTE 1
.SH NAME
route \- map orientations and great circle paths
.SH SYNOPSIS
.B route
[
.B -t
]
.SH DESCRIPTION
.I Route
without an option
reads from the standard input a sequence of points, expressed
as latitude-longitude pairs.
For each pair of points, say A and B,
.I route
prints on the standard output
.IP \-
A
.IR map (7)
orientation, expressed as a
.B -o
option, that transforms the great circle from A to B into the equator.
The transformed locations of A and B are located on the equator
at equal distances west and east of the Prime Meridian.
.IP \-
The transformed coordinates of the two points.
.IP \-
The same information for a map orientation in which point A
appears to the east and B to the west of the Prime Meridian.
.PP
Under option
.B -t
.I route
produces coordinates along the great circle from A to B
in the form of a track for use with
.I map
option
.BR -t .
.PP
Coordinates are expressed in degrees, with latitude
positive north of the equator and longitude positive
west of Greenwich.
.SH EXAMPLES
.HP
.B "echo 40.75 74 52 0 | route -t | map mercator -l 30 70 -10 80 -t - | plot
.br
Produce a map of the North Atlantic with a great circle plotted
from New York to London.
.TP
.B route
.br
.ns
.TP
.B 40.75 74 52 0
Produces the output
.RS
.IP
.nf
.ft L
-o 35.8283 -157.5308 -168.6148
A -0.0000 24.9943
B -0.0000 -24.9943
-o -35.8283 22.4692 168.6149
A -0.0000 -24.9943
B 0.0000 24.9943
.ft
.fi
.RE
.IP
From this we derive the following command to draw a strip map
20 degrees wide along the great circle from New York to London.
The
.B -w
option windows the map in the new coordinate system, where
the equator runs along the great circle and the two cities
sit at 25W and 25E on that `equator'.
The
.B -l
option avoids surveying the whole rest of the world for
plottable points.
.IP
.B
map mercator -o 35.83 -157.53 -168.61 -w -10 10 -30 30 -l 30 75 -10 80
.SH SEE ALSO
.IR map (7)
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