i.ortho.init - GRASS GIS manual

Note: This document is for an older version of GRASS GIS that is outdated.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

NAME

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

KEYWORDS

imagery, orthorectify

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 GUI dialog

Parameters:

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

DESCRIPTION
SEE ALSO
AUTHOR

DESCRIPTION

Aerial photographs may be either vertical or oblique. Vertical photographs can be truly vertical (nadir), or slightly tilted (less than 3 degree from the vertical). Usually aerial photos are tilted to some degree. We refer to the term vertical photograph up to a tilt of 3 degree.
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.

AUTHOR

Mike Baba, DBA Systems, Inc.

SOURCE CODE

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

Latest change: Thu Feb 3 11:10:06 2022 in commit: 73413160a81ed43e7a5ca0dc16f0b56e450e9fef