.TH d.rhumbline 1grass "" "GRASS 7.8.5" "GRASS GIS User's Manual"
.SH NAME
\fI\fBd.rhumbline\fR\fR  \- Displays the rhumbline joining two longitude/latitude coordinates.
.SH KEYWORDS
display, distance, rhumbline
.SH SYNOPSIS
\fBd.rhumbline\fR
.br
\fBd.rhumbline \-\-help\fR
.br
\fBd.rhumbline\fR \fBcoordinates\fR=\fIlon1,lat1,lon2,lat2\fR  [\fBline_color\fR=\fIname\fR]   [\-\-\fBhelp\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR]  [\-\-\fBui\fR]
.SS Flags:
.IP "\fB\-\-help\fR" 4m
.br
Print usage summary
.IP "\fB\-\-verbose\fR" 4m
.br
Verbose module output
.IP "\fB\-\-quiet\fR" 4m
.br
Quiet module output
.IP "\fB\-\-ui\fR" 4m
.br
Force launching GUI dialog
.SS Parameters:
.IP "\fBcoordinates\fR=\fIlon1,lat1,lon2,lat2\fR \fB[required]\fR" 4m
.br
Starting and ending coordinates
.IP "\fBline_color\fR=\fIname\fR" 4m
.br
Line color
.br
Either a standard color name or R:G:B triplet
.br
Default: \fIblack\fR
.SH DESCRIPTION
A rhumbline (loxodrome) is a line following a constant angle of the
compass (i.e., a line of constant direction). It crosses all meridians
at the same angle, i.e. a path of constant bearing.
\fId.rhumbline\fR displays the
rhumbline joining any two user\-specified points in the
active frame on the user\(cqs graphics monitor.  The named
coordinate locations must fall within the boundaries of the
user\(cqs current geographic region.
.PP
The user has to specify the starting and ending
longitude/latitude coordinates of the rhumbline and
(optionally) the color in which the rhumbline will be
displayed; in this case, the program will run
non\-interactively.
.SH EXAMPLE
A geodesic line if shown over the political map of the world
(demolocation dataset):
.br
.nf
\fC
g.region vector=country_boundaries \-p
d.mon wx0
d.vect country_boundaries type=area
d.rhumbline coordinates=55:58W,33:18S,26:43E,60:37N \(rs
  line_color=yellow
# show additionally 10 degree grid
d.grid 10
\fR
.fi
.PP
.br
\fIRhumbline (loxodrome)\fR
.SH NOTES
This program works only in GRASS locations with longitude/latitude
coordinate system.
.SH SEE ALSO
\fI
d.geodesic,
d.grid,
m.measure
\fR
.SH AUTHOR
Michael Shapiro, U.S. Army Construction Engineering Research Laboratory
.SH SOURCE CODE
.PP
Available at: d.rhumbline source code (history)
.PP
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.PP
© 2003\-2020
GRASS Development Team,
GRASS GIS 7.8.5 Reference Manual