d.rhumbline(1)

📦
version 8.4.2 · 8 versions
, in fedora 44

💫 d.rhumbline — the GRASS GIS User's Manual page, bestie edition 💫

okay so picture this: you're in GRASS GIS (the 8.4.2 Reference Manual, to be exact) and you want a cute lil line across your map. That's d.rhumbline, and she is so good at what she does. Let's get into it. 🫶

✨ NAME ✨

d.rhumbline — she displays the rhumbline joining two longitude/latitude coordinates. that's it, that's the job, and she eats every time. 💅

🏷️ KEYWORDS 🏷️

display, distance, rhumbline

(three little words and yet so much power tbh)

📜 SYNOPSIS 📜

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

like, yes bestie, it's giving "one required parameter and one optional one", we love a low-maintenance icon. ✨

🚩 Flags 🚩

  • --help — prints the usage summary, aka the "help me I forgot how this works" button. 🙈
  • --verbose — verbose module output. she's gonna tell you everything she's doing. main character energy fr fr.
  • --quiet — quiet module output. shhh, no talking, just vibes. 🤫
  • --ui — force launching the GUI dialog, for when you want the lil pop-up window instead of typing. 🎀

🎛️ Parameters 🎛️

  • coordinates=lon1,lat1,lon2,lat2 — required! the starting and ending coordinates. you literally cannot skip this one, bestie, she needs to know where the line goes. 📍
  • line_color=name — the line color. either a standard color name or an R:G:B triplet, so go wild. Default: black (classic, iconic, never misses). 🖤

📖 DESCRIPTION 📖

okay so a rhumbline — also called a loxodrome, which is such a fancy word, love that for her — is a line that follows a constant angle of the compass. basically it's a line of constant direction. 🌈

the way that it works: it crosses all meridians at the same angle. so yes, it's a path of constant bearing. periodt. 🧭

d.rhumbline displays the rhumbline joining any two user-specified points in the active frame on the user's graphics monitor. and here's the important bit: the named coordinate locations must fall within the boundaries of the user's current geographic region. no sneaking outside your region, she will not do it. 😭

you (the user) have to specify the starting and ending longitude/latitude coordinates of the rhumbline, and optionally the color in which the rhumbline will be displayed. and when you do that, the program runs non-interactively. slay. ✨

🧪 EXAMPLE 🧪

here's a geodesic line shown over the political map of the world (the demolocation dataset, iykyk):

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) 💫

📝 NOTES 📝

lowkey important: this program works only with a longitude/latitude coordinate system. don't try it with anything else, she's not built for that. 🙈

👀 SEE ALSO 👀

d.geodesic, d.grid, m.measure

(the girlies in the same friend group, go say hi)

👑 AUTHOR 👑

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

we stan. 💜

🔗 SOURCE CODE 🔗

Available at: d.rhumbline source code (history)

Accessed: Saturday Jan 17 05:40:37 2026

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

© 2003-2025 GRASS Development Team, GRASS GIS 8.4.2 Reference Manual

and that's the whole page, bestie!! this was GRASS 8.4.2, accessed Saturday Jan 17 05:40:37 2026 — go draw some rhumblines and absolutely devour. 💖✨🎀🦋🌸

📦 where this page comes from