i.ortho.camera(1grass)

💖 i.ortho.camera (1grass) — the GRASS manual, but make it make sense 💖

okay bestie, sit down, hydrate, and let me tell you about i.ortho.camera. it's a GRASS module, it lives in the imagery + orthorectify corner of the world, and it is literally the vibe check for your camera reference files. let's go 🦋

---

✨ NAME ✨

i.ortho.camera — select and modify the imagery group camera reference file.

🌸 KEYWORDS 🌸

imagery, orthorectify

---

👑 SYNOPSIS 👑

i.ortho.camera
i.ortho.camera --help
i.ortho.camera  [group=name]  camera=name  [name=string]   [id=string]
[clf=float]   [pp=east,north]   [fid=east,north[,east,north,...]]
[--help]  [--verbose]  [--quiet]  [--ui]

🎀 Flags 🎀

• --help — prints the usage summary, like a lil cheat sheet
• --verbose — verbose module output, so it tells you everything that's going on
• --quiet — quiet module output, the strong silent type
• --ui — forces the GUI dialog to launch, no cap

🧚 Parameters 🧚

• group=name — name of the imagery group for ortho-rectification
• camera=name — required!! name of the camera reference file. also known as: name of input file
• name=string — the camera name
• id=string — the camera id
• clf=float — calibrated focal length
• pp=east,north — principal point coordinates. coordinates, babe
• fid=east,north[,east,north,...] — fiducial coordinates. coordinates again 📍

---

💅 DESCRIPTION 💅

i.ortho.camera creates or modifies entries in a camera reference file. and why do we care, you ask? because for ortho-photo rectification, a camera reference file is required for computation of scanned image to photo-coordinate transformation parameters.

there are two coordinate systems in this situation, and yes it's giving complicated but stay with me:

• the image coordinate system — measured in pixels
• the photo coordinate system — measured in milli-meters

the inner orientation establishes a relation between the pixels and the image coordinates with help of fiducial marks. so basically the fiducial marks are the matchmakers here 💘

---

the first prompt in the program will ask you for the name of the camera reference file to be created or modified. you may create a new camera reference file by entering a new name, or modify an existing camera reference file by entering the name of an existing camera file. new file? new era. ✨

after entering the camera file name, following menu is displayed:

Please provide the following information

    CAMERA NAME:               camera name______
    CAMERA IDENTIFICATION:     identification___
    CALIBRATED FOCAL LENGTH mm.:_________________
    POINT OF SYMMETRY (X)   mm.:_________________
    POINT OF SYMMETRY (Y)   mm.:_________________
    MAXIMUM NUMBER OF FIDUCIALS:_________________
   AFTER COMPLETING ALL ANSWERS, HIT <ESC> TO CONTINUE
               (OR <Ctrl-C> TO CANCEL)

the camera name and identification describe the camera reference file. the calibrated focal length and the point of symmetry are used in computing the photo-to-target transformation parameters. these values should be entered from the camera calibration report — which, btw, is usually available from the photograph supplier. bestie. get the report. 📄

this example is the camera Zeiss LMK9 265-002A belonging to the Hellenic Military Geographical Survey (HMGS) and calibrated in December 1985. vintage but iconic, honestly.

the photo coordinate system origin is the so-called calibrated principal point (PP, Principal Point of Symmetry) which is in the center of the image. the origin of the axes is at the intersection of the radii traced from the fiducial marks. in the ideal case of no deviations in the camera (see camera calibration certificate) the center is the origin and the values are 0 for both X and Y of Point of Symmetry. but usually the principal point does not fall on the intersection of the radii at the center of the picture. this eccentricity is usually of the order of a few micrometers. tiny little diva offset 😭

you are then asked to enter the X and Y photo coordinates of each fiducial as follows. these fiducials (or reseau) marks are index marks imaged on film which serve as reference photo coordinate system. the maximum number of fiducials will determine the number of fiducial or reseau coordinate pairs to be entered below. the origin is the center of the image (or the point of symmetry) and X and Y are left-right and up-down. the order is up to the user, but must be kept consistent throughout the rectification process. consistency is the whole assignment, periodt.

on this screen you should enter the fiducial or reseau photo-coordinates as given in the camera calibration report. the X, and Y coordinates are in milli-meters from the principle point.

Please provide the following information
    Fid#    FID ID          X          Y
    1__    _____        0.0___    0.0___
    2__    _____        0.0___    0.0___
    3__    _____        0.0___    0.0___
    4__    _____        0.0___    0.0___
    5__    _____        0.0___    0.0___
    6__    _____        0.0___    0.0___
    7__    _____        0.0___    0.0___
    8__    _____        0.0___    0.0___
    9__    _____        0.0___    0.0___
    10_    _____        0.0___    0.0___
             next:  end__
    AFTER COMPLETING ALL ANSWERS, HIT <ESC> TO CONTINUE
                    (OR <Ctrl-C> TO CANCEL)

the input display is repeated until the number of MAXIMUM FIDUCIALS is reached. so yes, buckle up, you're doing this ten times minimum. 🫶

---

🔥 SEE ALSO 🔥

• i.ortho.photo
• g.gui.photo2image
• g.gui.image2target
• i.ortho.init

go read those too, iykyk 🦋

---

🌈 AUTHOR 🌈

Mike Baba, DBA Systems, Inc. — thank you for your service, king 👑

---

💜 SOURCE CODE 💜

Available at: i.ortho.camera source code (history)

Latest change: Thursday May 08 14:35:40 2025 in commit: 9528b1e38ba37992c1597a979dc3efbb07b74ec5

Main index | Imagery index | Topics index | Keywords index | Graphical index | Full index

---

and that's the whole thing bestie, you ate. 💅✨

© 2003-2026 GRASS Development Team, GRASS 8.5.0 Reference Manual — no cap, that's the 411 from the GRASS 8.5.0 manual, dated and everything, mwah 💖🎀