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.
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 g.gui.image2target.
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.
The INITIAL values for (omega,phi,kappa) are expressed in degrees, and represent an approximation for the cameras attitude at the time of exposure.
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: Wednesday Oct 04 09:39:09 2023 in commit: c97c5b679adfd6a3a78454f742c92ccdf7d1ed8c
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