i.ortho.init(1grass)

✨ i.ortho.init ✨

okay bestie, welcome to the GRASS User's Manual, this one's i.ortho.init and it's genuinely iconic for aerial photo girlies 💖

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🌸 NAME 🌸

i.ortho.init — she interactively creates or modifies entries in a camera initial exposure station file for the imagery group referenced by a sub-block. no cap 💅

🎀 KEYWORDS 🎀

imagery, orthorectify

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🦋 SYNOPSIS 🦋

i.ortho.init
i.ortho.init --help
i.ortho.init [-rp] group=name  [xc=float]   [yc=float]   [zc=float]
[xc_sd=float]   [yc_sd=float]   [zc_sd=float]   [omega=float]
[phi=float]   [kappa=float]   [omega_sd=float]   [phi_sd=float]
[kappa_sd=float]   [--help]  [--verbose]  [--quiet]  [--ui]

🌈 Flags:

• -r — use initial values at run time 🫶
• -p — print initial values 👑
• --help — print usage summary
• --verbose — verbose module output 🗣️
• --quiet — quiet module output 🤫
• --ui — force launching the GUI dialog 🖥️

🍓 Parameters:

• group=name [required] — name of the imagery group for ortho-rectification. this one is literally mandatory, you can't skip her 💀
• xc=float — initial Camera Exposure X-coordinate
• yc=float — initial Camera Exposure Y-coordinate
• zc=float — initial Camera Exposure Z-coordinate
• xc_sd=float — apriori X-coordinate standard deviation
• yc_sd=float — apriori Y-coordinate standard deviation
• zc_sd=float — apriori Z-coordinate standard deviation
• omega=float — initial Camera Omega (pitch) degrees
• phi=float — initial Camera Phi (roll) degrees
• kappa=float — initial Camera Kappa (yaw) degrees
• omega_sd=float — apriori Omega (pitch) standard deviation
• phi_sd=float — apriori Phi (roll) standard deviation
• kappa_sd=float — apriori Kappa (yaw) standard deviation

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💜 DESCRIPTION 💜

so aerial photographs can be either vertical or oblique, and that distinction is the whole plot of this module, bestie. Vertical photographs can be truly vertical (nadir), or just slightly tilted — less than 3 degree from the vertical. Usually aerial photos are tilted to some degree, that's just how it is. the term "vertical photograph" covers you up to a tilt of 3 degree. 🛩️

Oblique aerial photographs, on the other hand, are purposely taken with an angle between 3 and 90 degree from the nadir direction. on purpose! intentional! main character energy ✨

The use of i.ortho.init (menu 6) is only required when rectifying a tilted or oblique aerial photo. so if yours is straight-up vertical, you can lowkey chill 🙈

i.ortho.init creates or modifies entries in a camera initial exposure station file for the imagery group referenced by a sub-block. these entries include:

• the (XC,YC,ZC) standard (e.g. UTM) approximate coordinates of the camera exposure station 💫
• initial roll, pitch, and yaw angles (in degrees) of the camera's attitude 🌀
• the a priori standard deviations for these parameters 📏

During the imagery program i.ortho.rectify, the initial camera exposure station file is used for computation of the ortho-rectification parameters. and if no initial camera exposure station file exist, the default values are computed from the control points file created in g.gui.image2target. periodt. 💅

The following menu is displayed:

        Please provide the following information
    INITIAL XC: Meters                __________
    INITIAL YC: Meters                __________
    INITIAL ZC: Meters                __________
    INITIAL omega (pitch) degrees:    __________
    INITIAL phi  (roll) degrees:      __________
    INITIAL kappa  (yaw) degrees:     __________
    Standard Deviation XC: Meters     __________
    Standard Deviation YC: Meters     __________
    Standard Deviation ZC: Meters     __________
    Std. Dev. omega (pitch) degrees:  __________
    Std. Dev. phi  (roll) degrees:    __________
    Std. Dev. kappa  (yaw) degrees:   __________
        Use these values at run time? (1=yes, 0=no)
     AFTER COMPLETING ALL ANSWERS, HIT <ESC> TO CONTINUE
                  (OR <Ctrl-C> TO CANCEL)

The INITIAL values for (XC,YC,ZC) are expressed in standard (e.g. UTM) coordinates, and represent an approximation for the location of the camera at the time of exposure. 📸

• X: East aircraft position
• Y: North aircraft position
• Z: Flight altitude above sea level ✈️

The INITIAL values for (omega,phi,kappa) are expressed in degrees, and represent an approximation for the camera's attitude at the time of exposure.

• Omega (pitch): raising or lowering of the aircraft's front (turning around the wings' axis) 🎢
• Phi (roll): raising or lowering of the wings (turning around the aircraft's axis) 🦋
• Kappa (yaw): rotation needed to align the aerial photo to true north — needs to be denoted as +90 degree for a clockwise turn and -90 degree for a counterclockwise turn 🧭

If ground control points are available, the INITIAL values are iteratively corrected. this is particularl useful when the INITIAL values are rather rough estimates. slay, she self-corrects 💅

The standard deviations for (XC,YC,ZC) are expressed in meters, and are used as a priori values for the standard deviations used in computation of the ortho rectification parameters. Higher values improve the refinement of the initial camera exposure. as a rule of thumb, 5% of the estimated target extents should be used. write that down bestie 📝

The standard deviations for (omega,phi,kappa) are expressed in degrees, and are used as a priori values for the standard deviations used in computation of the ortho rectification parameters. as a rule of thumb, 2 degrees should be used. 🌡️

⚠️ If Use these values at run time? (1=yes, 0=no) is set to 0, the values in this menu are not used. like, at all. not even a little. 🙈

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👑 SEE ALSO 👑

i.ortho.photo, g.gui.photo2image, g.gui.image2target, i.ortho.elev, i.ortho.camera, i.ortho.transform, i.ortho.rectify

the whole friend group fr fr 🫶

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💖 AUTHOR 💖

Mike Baba, DBA Systems, Inc. — king behaviour, we respect it 👑

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⭐ SOURCE CODE ⭐

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

Latest change: Monday Jun 16 12:59:41 2025 in commit: a7933d29f692c91f7ed0826e2f05fc108b9f1653

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

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and that's the whole vibe check bestie ✨ this was i.ortho.init from the GRASS 8.5.0 Reference Manual, © 2003-2026 GRASS Development Team, last touched Monday Jun 16 12:59:41 2025 in commit a7933d29f692c91f7ed0826e2f05fc108b9f1653 — go forth and orthorectify, you've got this 💅🎀🦋