Note: This document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade, and read the current manual page.

**-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 GUI dialog

**group**=*name***[required]**- Name of imagery group for ortho-rectification
**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

Oblique aerial photographs are purposely taken with an angle between 3 and 90 degree from the nadir direction.

**The use of i.ortho.init (menu 6) is only required when rectifying a
tilted or oblique aerial photo.**

*i.ortho.init* creates or modifies entries in a camera initial exposure
station file for 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 cameras
attitude; and the *a priori* standard deviations for these
parameters. During the imagery program, *i.photo.rectify*, the initial camera
exposure station file is used for computation of the ortho-rectification
parameters. If no initial camera exposure station file exist, the default
values are computed from the control points file created in *i.photo.2target*.

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 cameras 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 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.

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.

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.

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

Latest change: Monday Mar 23 08:34:07 2020 in commit: 8c741fac7ab44ba5ac9586af875019111a00f778

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© 2003-2023 GRASS Development Team, GRASS GIS 7.8.9dev Reference Manual