d.rhumbline(1grass)

💅 d.rhumbline — the GRASS User's Manual glow-up

okay bestie, welcome to d.rhumbline(1grass) 🎀 this is the GRASS User's Manual page for a lil display module that draws a rhumbline between two lon/lat points. yes it's niche. yes it's iconic. let's get into it. 🦋

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✨ NAME ✨

d.rhumbline — draws the rhumbline that connects two longitude/latitude coordinates. that's it, that's the whole job, and she does it flawlessly. 💅

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🔑 KEYWORDS 🔑

display, distance, rhumbline

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📜 SYNOPSIS 📜

d.rhumbline
d.rhumbline --help
d.rhumbline coordinates=lon1,lat1,lon2,lat2  [line_color=name]
[--help]  [--verbose]  [--quiet]  [--ui]

🚩 Flags 🚩

• --help — prints the usage summary, aka the receipts 📝
• --verbose — verbose module output, she tells you everything 🗣️
• --quiet — quiet module output, she says nothing, mysterious queen 🙈
• --ui — forces the GUI dialog to launch, window pop-up moment 🪟

🎀 Parameters 🎀

• coordinates=lon1,lat1,lon2,lat2 — required 🫶 the starting and ending coordinates. you literally have to give her these, no skipping.
• line_color=name — the color of the line. either a standard color name or an R:G:B triplet. Default: black 🖤

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📖 DESCRIPTION 📖

so a rhumbline (also called a loxodrome, fancy 🧚) is a line that follows a constant angle of the compass — like, a line of constant direction, periodt. it crosses every meridian at the same angle, which means it's a path of constant bearing. no cap. 🧭

d.rhumbline displays the rhumbline joining any two user-specified points in the active frame on your graphics monitor. and listen — the named coordinate locations must fall within the boundaries of your current geographic region. if they don't, that's a vibe check failure, sorry bestie. 😭

you have to specify the starting and ending longitude/latitude coordinates of the rhumbline, and (optionally) the color she'll be drawn in. if you give her the color, the program runs non-interactively. slay. ✨

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🍓 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
d.rhumbline coordinates=55:58W,33:18S,26:43E,60:37N \
  line_color=yellow
# show additionally 10 degree grid
d.grid 10

Rhumbline (loxodrome)

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📌 NOTES 📌

this program works only with longitude/latitude coordinate system. only. that one. don't try anything else, she will not be entertaining it. 💀

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👀 SEE ALSO 👀

d.geodesic, d.grid, m.measure

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👑 AUTHOR 👑

Michael Shapiro, U.S. Army Construction Engineering Research Laboratory — king behavior, honestly. 🫡

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💻 SOURCE CODE 💻

Available at: d.rhumbline source code (history)

Latest change: Friday Apr 17 01:04:26 2026 in commit: 32a143358df26b2e518b03c7e0d79541e8d1e5b1

Main index | Display index | Topics index | Keywords index | Graphical index | Full index

© 2003-2026 GRASS Development Team, GRASS 8.5.0 Reference Manual

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and that's the whole page, bestie!! 🌸 this was GRASS 8.5.0, dated Friday Apr 17 01:04:26 2026, and it's all brought to you by the GRASS Development Team with love (© 2003-2026). go draw a line on a map. you deserve it. 💖✨🌈