PROJ(1)

📦

version 9.8.1 · 6 versions

💖 PROJ(1) 💖

okay bestie, sit DOWN, because today we're talking about proj — yes, the cartographic projection filter, and yes, it is lowkey iconic and highkey underrated. This page is the proj(1) manual, and I'm about to make it make sense for you. 🎀

✨ NAME ✨

proj — cartographic projection filter 🌍✨

🌸 SYNOPSIS 🌸

proj [-beEfiIlmorsStTvVwW] [args]] ([+opt[=arg] ...] | {crs}) file
...

invproj [-beEfiIlmorsStTvVwW] [args]] ([+opt[=arg] ...] | {crs}) file
...

💅 DESCRIPTION 💅

proj and invproj do the forward and inverse conversion of cartographic data to or from cartesian data, with a whole menu of selectable projection functions. pick your fave, fr fr. 🔥

ngl, invproj may not be available on all platforms — no cap. if it's not there for you, just use proj -I instead. periodt.

The following control parameters can appear in any order (chaos-friendly, we love that for us):

-b — special option for binary coordinate data input and output through standard input and standard output. data is assumed to be in system type double floating point words. this one's for when proj is a child process, and it lets you bypass formatting operations. ✨
-d <n> — Added in version 5.2.0: specify the number of decimals to round to in the output. 🎀
-i — selects binary input only (see -b). 🙈
-I — alternate method to specify inverse projection. redundant when used with invproj. 💀
-o — selects binary output only (see -b). 🦋
-t<a> — where a specifies a character employed as the first character to denote a control line to be passed through without processing. this option is applicable to ASCII input only. (# is the default value). 🌸
-e <string> — where string is an arbitrary string to be output if an error is detected during data transformations. the default value is a three character string: *\t*. note that if the -b, -i or -o options are employed, an error is returned as HUGE_VAL value for both return values. 😭
-E — causes the input coordinates to be copied to the output line prior to printing the converted values. 🫶
-l<[=id]> — list projection identifiers that can be selected with +proj. proj -l=id gives expanded description of projection id, e.g. proj -l=merc. ⭐
-lp — list of all projection id that can be used with the +proj parameter. equivalent to proj -l. 💜
-lP — expanded description of all projections that can be used with the +proj parameter. 👑
-le — list of all ellipsoids that can be selected with the +ellps parameters. 🌈
-lu — list of all distance units that can be selected with the +units parameter. 💖
-r — this option reverses the order of the expected input from longitude-latitude or x-y to latitude-longitude or y-x. 🔄
-s — this option reverses the order of the output from x-y or longitude-latitude to y-x or latitude-longitude. 🔄
-S — causes estimation of meridional and parallel scale factors, area scale factor and angular distortion, and maximum and minimum scale factors to be listed between <> for each input point. for conformal projections meridional and parallel scales factors will be equal and angular distortion zero. equal area projections will have an area factor of 1. 🧚
-m <mult> — the cartesian data may be scaled by the mult parameter. when processing data in a forward projection mode the cartesian output values are multiplied by mult, otherwise the input cartesian values are divided by mult before inverse projection. if the first two characters of mult are 1/ or 1: then the reciprocal value of mult is employed. ✨
-f <format> — where format is a printf format string to control the form of the output values. for inverse projections, the output will be in degrees when this option is employed. the default format is "%.2f" for forward projection and DMS for inverse. 🎀
-w<n> — where n is the number of significant fractional digits to employ for seconds output (when the option is not specified, -w3 is assumed). 🍓
-W<n> — where n is the number of significant fractional digits to employ for seconds output. when -W is employed the fields will be constant width with leading zeroes. 🍓
-v — causes a listing of cartographic control parameters tested for and used by the program to be printed prior to input data. 👀
-V — this option causes an expanded annotated listing of the characteristics of the projected point. -v is implied with this option. 💅

The +opt run-line arguments are associated with cartographic parameters. additional projection control parameters may be contained in two auxiliary control files: the first is optionally referenced with the +init=file:id and the second is always processed after the name of the projection has been established from either the run-line or the contents of +init file. the environment parameter PROJ_DATA establishes the default directory for a file reference without an absolute path. this is also used for supporting files like datum shift files. 🗂️✨

Added in version 9.3.0: {crs} is one of the possibilities accepted by :c:proj_create(), provided it expresses a projected CRS, like a WKT string, an object code (like "EPSG:32632") a PROJJSON string, etc. the projection computed will be those of the map projection implied by the transformation from the base geographic CRS of the projected CRS to the projected CRS. 🌐💜

One or more files (processed in left to right order) specify the source of data to be converted. a - will specify the location of processing standard input. if no files are specified, the input is assumed to be from stdin. for ASCII input data the two data values must be in the first two white space separated fields and when both input and output are ASCII all trailing portions of the input line are appended to the output line. 📄

Input geographic data (longitude and latitude) must be in DMS or decimal degrees format and input cartesian data must be in units consistent with the ellipsoid major axis or sphere radius units. output geographic coordinates will be in DMS (if the -w switch is not employed) and precise to 0.001" with trailing, zero-valued minute-second fields deleted. 🎯

🌈 EXAMPLE 🌈

The following script

proj +proj=utm +zone=12 -r <<EOF
45d15'33.1" 111.5W
45d15.551666667N -111d30
+45.25919444444 111d30'000w
EOF

will perform UTM zone 12 forward projection. the default +ellps=GRS80 is used as no +ellps was specified. the geographic values of this example are equivalent and meant as examples of various forms of DMS input. the x-y output data will appear as three lines of:

460770.43     5011865.86

This other example

proj EPSG:6421 -V <<EOF
-120 35.8
EOF

Will perform the projection of the coordinates in "NAD83(2011) / California zone 4" (EPSG:6421) into its geographic system, "NAD83(2011)", showing the expanded annotated listing. the output will appear as:

#Lambert Conformal Conic
#   Conic, Sph&Ell
#   lat_1= and lat_2= or lat_0, k_0=
# +proj=lcc +lat_0=35.3333333333333 +lon_0=-119 +lat_1=37.25 +lat_2=36
# +x_0=2000000 +y_0=500000 +ellps=GRS80
#Final Earth figure: ellipsoid
#  Major axis (a): 6378137.000
#  1/flattening: 298.257222
#  squared eccentricity: 0.006694380023
Longitude: 120dW [ -120 ]
Latitude:  35d48'N [ 35.8 ]
Easting (x):   1909606.87
Northing (y):  552253.58
Meridian scale (h) : 1.00004382  ( 0.004382 % error )
Parallel scale (k) : 1.00004382  ( 0.004382 % error )
Areal scale (s):     1.00008765  ( 0.008765 % error )
Angular distortion (w): 0.000
Meridian/Parallel angle: 90.00000
Convergence : -0d35'47.714" [ -0.59658715 ]
Max-min (Tissot axis a-b) scale error: 1.00004 1.00004

🦋 OTHER PROGRAMS 🦋

The proj program is limited to converting between geographic and projected coordinates within one datum. that's the boundary, bestie, she stays in her lane. 💅

The cs2cs program operates similarly, but allows translation between any pair of definable coordinate reference systems, including support for datum translation. she's the versatile one. 👑

👀 SEE ALSO 👀

cs2cs(1), cct(1), geod(1), gie(1), projinfo(1), projsync(1)

💀 BUGS 💀

A list of known bugs can be found at https://github.com/OSGeo/PROJ/issues where new bug reports can be submitted to. not me reading the issue tracker like it's a group chat 🙈

🌐 HOME PAGE 🌐

https://proj.org/

🎀 Author 🎀

Gerald I. Evenden

💜 Copyright 💜

1983-2026, PROJ contributors

and that's the whole thing, bestie — PROJ version 9.8, dated 10 avril 2026. you're now officially fluent in proj(1). go project something slay. 👑✨🦋

📦 where this page comes from

ubuntu stonking: proj-bin 9.8.1-1 · MIT
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-10-18: a language model's rewrite of the original, under its terms