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NAME
i.ortho.photo - Menu driver for the photo imagery programs.
KEYWORDS
imagery, orthorectify
SYNOPSIS
i.ortho.photo
i.ortho.photo help
i.ortho.photo group=name [--verbose] [--quiet]
Parameters:
- group=name
- Name of imagery group for ortho-rectification
DESCRIPTION
i.ortho.photo
allows the user to ortho-rectify imagery group files.
An imagery group consists of several scanned aerial photographs
(raster maps) of a common area.
Imagery groups can be created or modified using the
GRASS Image Processing Program
i.group,
or using the first menu option described below.
i.ortho.photo guides the user through the steps required to
ortho-rectify the raster maps in a single imagery group.
The first menu in i.ortho.photo provides the user with the following
options:
- Initialization Options:
-
1) Select/Modify imagery group
2) Select/Modify imagery group target
3) Select/Modify target elevation model
4) Select/Modify imagery group camera
- Transformation Parameter Computation:
-
5) Compute image-to-photo transformation parameters
6) Initialize exposure station parameters
7) Compute photo-to-target transformation parameters
- Ortho-rectification Option:
-
8) Ortho-rectify imagery group raster maps
- RETURN to exit
- >
To ortho-rectify aerial images the user has to follow the menu options step by
step. Generally the user builds a target location containing a projected DEM
and a map reference (topo sheet or other map). Another xy-location will
contain the aerial photo. The entire rectification process is started within
the xy-location. First the target to the projected location has to be set
(i.target), then the image references (fiducial points) will be defined. After
describing the camera parameters, reference points from aerial image to the
topo sheet from the target location will be set. The local elevation will be
taken from the target DEM. Finally the aerial image will be rectified.
The options to follow are described as follows:
- 1. Select/Modify imagery group
- The current imagery group is display at the top of the
previous menu. You may select another (new or existing)
imagery group for the ortho-rectification program using
option (1). After choosing option (1) you will be prompted
for the name of a new or existing imagery group. Option
(1) using the GRASS Image Processing Program
i.group,
for creation or modification of imagery groups. For more
information on imagery group creation or modification
please the the GRASS manual page for
i.group.
- 2. Select/Modify imagery group target
- The target location and mapset may be selected or
modified using option (2). After choosing option (2) you
will be prompted for the names of the target location and
mapset, where the ortho-rectified raster maps will
reside. The target location is also the location from
which the elevation model (raster map) will be selected --
see option (3). Option (2) uses the GRASS Image Processing
Program
i.target,
for selection or
modification of the imagery group target location and mapset.
For more information on imagery group
selection or modification please the the GRASS manual page for
i.target.
- 3. Select/Modify target elevation model
- Option (3) allows you to select the raster map from
the target location to be used as the elevation model. The
elevation model is required for both the computation of
photo-to-target parameters (option 6) and for the
ortho-rectification of the imagery group files (option 8).
The raster map select for the elevation model should cover
the entire area of the image group to be ortho-rectified.
Currently, the elevation model raster map is expected to
be in units of meters. DTED and DEM files are suitable for
use as the elevation model in the ortho-rectification
program. After selection option (3) you will be prompted
for the name of the raster map in the target location that
you want to use as the elevation model.
- 4. Select/Modify imagery group camera
- Using option (4) you may select or create an camera
reference file that will be used with the current imagery
group. A camera reference file contains information on the
internal characteristics of the aerial camera, as well as
the geometry of the fiducial or reseau marks. The most
important characteristic of the camera is its focal
length. Fiducial or reseau marks locations are required to
compute the scanned image to photo-coordinate
transformation parameter (option 5). For a more detailed
description of option (4) please see the GRASS manual page
for
i.photo.camera.
- 5. Compute image-to-photo transformation parameters
- The scanned image to photo-coordinate transformation
parameters are computed using option (5). In this
interactive option you associate scanned reference points
(fiducials, reseau marks, etc.) with their known photo
coordinates from the camera reference file. Complete
documentation for this option is available under the manual
entry
i.photo.2image.
- 6. Initialize exposure station parameters
- If option (6) is selected, initial camera exposure
station parameters and initial variances may be selected or
modified. Complete documentation for this option is
available under the manual entry
i.photo.init.
- 7. Compute photo-to-target transformation parameters
- The photo to target transformation parameters are
compute using option (7). Here control points are marked on
one or more imagery group files and associated with there
known standard (e.g. UTM) and elevation coordinates. Complete
documentation for this option is available under the manual
entry
i.photo.2target.
- 8. Ortho-photo imagery group files
- Option (8) is used to perform the actual image
ortho-rectification after all of the transformation
parameters have been computed. Ortho-rectified raster
files will be created in the target location for each
selected imagery group file. You may select either the
current window in the target location or the minimal
bounding window for the ortho-rectified image. Complete
documentation for this option is available under the manual
entry
i.photo.rectify.
NOTES
i.ortho.photo currently requires the elevation
model to be in meters, and the target location to be a standard (e.g. UTM)
coordinate system.
REFERENCES
- Wolf, P.R. (1983): Elements of Photogrammetry, With Air Photo Interpretation and Remote Sensing. 2nd ed. McGraw Hill, 562 pages
- Rocchini, D., Metz, M., Frigeri, A., Delucchi, L., Marcantonio, M., Neteler, M. (2012).
Robust rectification of aerial photographs in an open source environment. Computers & Geosciences 39 (2): 145-151.
SEE ALSO
i.photo.camera,
i.photo.2image,
i.photo.2target,
i.photo.init,
i.photo.rectify
AUTHOR
Mike Baba, DBA Systems, Inc.
Updated rectification and elevation map to FP 1/2002 Markus Neteler
Last changed: $Date: 2012-01-08 13:48:21 -0800 (Sun, 08 Jan 2012) $
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