d.geodesic - GRASS manual
Author: GRASS Development Team
Description: d.geodesic: Displays a geodesic line, tracing the shortest distance between two geographic points along a great circle, in a longitude/latitude data set.
Keywords: display, distance, great circle, shortest path

## NAME

d.geodesic - Displays a geodesic line, tracing the shortest distance between two geographic points along a great circle, in a longitude/latitude data set.

## KEYWORDS

display, distance, great circle, shortest path

## SYNOPSIS

d.geodesic
d.geodesic --help
d.geodesic coordinates=lon1,lat1,lon2,lat2 [line_color=name] [text_color=name] [units=string] [--help] [--verbose] [--quiet] [--ui]

### Flags:

--help
  Print usage summary
--verbose
  Verbose module output
--quiet
  Quiet module output
--ui
  Force launching GUI dialog

### Parameters:

coordinates=lon1,lat1,lon2,lat2 [required]
  Starting and ending coordinates
line_color=name
  Line color
  Either a standard color name or R:G:B triplet
  Default: black
text_color=name
  Text color
  Either a standard color name or R:G:B triplet
units=string
  Units
  Units
  Options: meters, kilometers, feet, miles
  Default: meters

## DESCRIPTION

d.geodesic displays a geodesic line in the active frame on the user's graphics monitor. This is also known as the great circle line and traces the shortest distance between two user-specified points on the curved surface of a longitude/latitude data set. The two coordinate locations named must fall within the boundaries of the user's current geographic region.

## OPTIONS

By default black line color and red text color will be used.

By indicating the starting and ending coordinates of the geodesic, the line and its length (by default in meters) are displayed to the graphical output. If the text color is set to none, the great circle distance is not displayed.

## EXAMPLE

A geodesic line if shown over the political map of the world (demolocation dataset):

    g.region vector=country_boundaries -p
    d.mon wx0
    d.vect country_boundaries type=area
    # show additionally a 20 degree grid
    d.grid 20

    d.geodesic coordinates=55:58W,33:18S,26:43E,60:37N \
      line_color=yellow text_color=red units=kilometers

Geodesic line (great circle line)

## NOTES

This program works only with longitude/latitude coordinate system.

## SEE ALSO

d.rhumbline, d.grid, m.measure

## AUTHOR

Michael Shapiro, U.S. Army Construction Engineering Research Laboratory

## SOURCE CODE

Available at: d.geodesic source code (history)

Latest change: Thursday May 08 14:17:52 2025 in commit: 3caa352f78f86a51ca463a6f1ba7ffe3db9771df

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