Ubuntu Manpage: i.ortho.photo - Menu driver for the photo imagery programs.

NAME

       i.ortho.photo  - Menu driver for the photo imagery programs.

KEYWORDS

       imagery, orthorectify, geometry

SYNOPSIS

       i.ortho.photo
       i.ortho.photo --help
       i.ortho.photo group=name productname=string  [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       --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

       productname=string [required]
           Name of Modules
           Options:  i.group,  i.ortho.target,  i.ortho.elev,  i.ortho.camera, g.gui.photo2image,
           i.ortho.init, g.gui.image2target, i.ortho.rectify
           i.group: 1 - Select/Modify imagery group
           i.ortho.target: 2 - Select/Modify imagery group target
           i.ortho.elev: 3 - Select/Modify target elevation model
           i.ortho.camera: 4 - Select/Modify imagery group camera
           g.gui.photo2image: 5 - Compute image-to-photo transformation
           i.ortho.init: 6 - Initialize exposure station parameters
           g.gui.image2target: 7 - Compute ortho-rectification parameters
           i.ortho.rectify: 8 - Ortho-rectify imagery files

DESCRIPTION

       i.ortho.photo is a menu to launch the different parts of the ortho  rectification  process
       of  aerial  imagery.  i.ortho.photo  allows  the user to ortho-rectify imagery group files
       consisting of  several  scanned  aerial  photographs  (raster  maps)  of  a  common  area.
       i.ortho.photo guides the user through 8 steps required to ortho-rectify the raster maps in
       a single imagery group. Alternatively, all  the  steps  can  be  performed  separately  by
       running the appropriate modules.

           •   Initialization Options

           •   Create/Modify imagery group to be orthorectified: i.group

           •   Select/Modify   target  project  (formerly  known  as  location)  and  mapset  for
               orthorectification: i.ortho.target

           •   Select/Modify target elevation model used for orthorectification: i.ortho.elev

           •   Create/Modify camera file of imagery group: i.ortho.camera

           •   Transformation Parameters Computation

           •   Compute image-to-photo transformation: g.gui.photo2image

           •   Initialize parameters of camera: i.ortho.init

           •   Compute   ortho-rectification   parameters    from    ground    control    points:
               g.gui.image2target

           •   Ortho-rectification

           •   Ortho-rectify imagery group: i.ortho.rectify

       The  ortho-rectification  procedure in GRASS GIS places the image pixels on the surface of
       the earth by matching  the  coordinate  system  of  the  aerial  image  in  pixels  (image
       coordinate  system)  and  the coordinate system of the camera sensor in millimetres (photo
       coordinate system) for  the  interior  orientation  of  the  image,  and  further  to  the
       georeferenced  coordinate  system  defined  by  projection  parametres  (target coordinate
       system) for exterior orientation.

EXAMPLE

Five groups of input parameters are required for ortho-rectification:

• Aerial image (images),

• Exposure and characteristics of the camera, i.e. its coordinates in target
coordinate system and height above sea level, focal length, yaw, pitch and roll,
dimensions of the camera sensor and resolution of aerial images,

• Reference surface, i.e. digital elevation model in the target coordinate system
used to normalize the terrain undulation,

• Topographic reference map used to find corresponding ground control points and/or,

• Coordinates of ground control points in the target coordinate system.
Example of an input oblique image in a source project

To ortho-rectify aerial images the user has to follow the menu options step by step.
Alternatively, all the steps can be performed separately by running the corresponding
modules.

The aerial photos shall be stored in a source project - a general Cartesian coordinate
system (XY). Digital elevation model and a map reference (topo sheet or other map used for
ground control point matching) shall be stored in a target project in a real-world
coordinate system (e.g. ETRS33).

The steps to follow are described below:

1 Create/Modify imagery group to be orthorectified: i.group

This step is to be run in the source project.

In this first step an imagery group of aerial images for ortho-rectification is created or
modified. The current imagery group is displayed at the top of the menu. You may select a
new or existing imagery group for the ortho-rectification. After choosing this option you
will be prompted for the name of a new or existing imagery group. As a result, a new file
mapset/group/name_of_group/REF is created that contatins the names of all images in a
group.
IMG_0020 source_mapset
IMG_0021 source_mapset
IMG_0022 source_mapset

2 Select/Modify target project and mapset for orthorectification: i.ortho.target

This step is to be run in the source project.

The target project and mapset may be selected or modified in Step 2. You will be prompted
for the names of the projected target project and mapset where the ortho-rectified raster
maps will reside. The target project is also the project from which the elevation model
(raster map) will be selected (see Step 3). In Step 2, a new file
mapset/group/name_of_group/TARGET is created contatining the names of target project and
mapset.
ETRS_33N
target_mapset

3 Select/Modify target elevation model used for orthorectification: i.ortho.elev

This step is to be run in the source project.

Step 3 allows you to select the raster map from the target project to be used as the
elevation model. The elevation model is required for both the computation of
photo-to-target parameters (Step 6) and for the ortho-rectification of the imagery group
files (Step 8). The raster map selected for the elevation model should cover the entire
area of the image group to be ortho-rectified. DTED and DEM files are suitable for use as
elevation model in the ortho-rectification program. In Step 3 you will be prompted for
the name of the raster map in the target project that you want to use as the elevation
model. As a result of this step, a new file mapset/group/name_of_group/ELEVATION is
created contatining the name and mapset of the chosen DEM.
elevation layer :ELEVATION
mapset elevation:target_mapset
location :ETRS_33N
math expression :(null)
units :(null)
no data values :(null)

4
Create/Modify camera file of imagery group: i.ortho.camera

This step is to be run in the source project.

In Step 4 you may select or create a 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 (Step 5). Two new files are created in this step: a file
mapset/group/name_of_group/CAMERA, contatining the name of the reference camera and a file
mapset/camera/name_of_reference, contatining the camera parameters.
CAMERA NAME sony
CAMERA ID 123
CAMERA XP 0
CAMERA YP 0
CAMERA CFL 16
NUM FID 4
0 -11.6 0
1 0 7.7
2 11.6 0
3 0 -7.7

5
Compute image-to-photo transformation: g.gui.photo2image

This step is to be run in the source project.

The scanned image to photo coordinate transformation parameters, i.e. the "interior
orientation", is computed in Step 5. In this interactive step you associate the scanned
reference points (fiducials, reseau marks, etc.) with their known photo coordinates from
the camera reference file. A new file mapset/group/name_of_group/REF_POINTS is created,
contatining a list of pairs of coordinates in image and photo coordinate systems.
# Ground Control Points File
#
# target location: XY
# target mapset: source_mapset
# source target status
# east north east north (1=ok, 0=ignore)
#-------------------------------------------------------------
0 1816 -11.6 0.0 1
2728 3632 0.0 7.7 1
5456 1816 11.6 0.0 1
2728 0.0 0.0 -7.7 1
Step 5: Image-to-photo transformation of an oblique image

6
Initialize parameters of camera: i.ortho.init

This step is to be run in the source project.

In Step 6, initial camera exposure station parameters and initial variances may be
selected or modified.

• X: East aircraft position;

• Y: North aircraft position;

• Z: Flight height above surface;

• 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° for clockwise turn and -90° for a counter-clockwise turn.
Principle of pitch and yaw

In Step 6, a new file mapset/group/name_of_group/INIT_EXP is created, contatining camera
parameters.
INITIAL XC 215258.345387
INITIAL YC 6911444.022270
INITIAL ZC 1101.991120
INITIAL OMEGA 0.000000
INITIAL PHI -0.168721
INITIAL KAPPA 3.403392
VARIANCE XC 5.000000
VARIANCE YC 5.000000
VARIANCE ZC 5.000000
VARIANCE OMEGA 0.000000
VARIANCE PHI 0.020153
VARIANCE KAPPA 0.017453
STATUS (1=OK, 0=NOT OK) 0

7
Compute ortho-rectification parameters from ground control points:
g.gui.image2target

This step is to be run in the target project.

The photo to target transformation parameters, i.e. the "exterior orientation", is
computed in Step 7. In this interactive step, control points are marked on one or more
imagery group files and associated with the known standard (e.g. UTM) and elevation
coordinates. Reasonable rectification results can be obtained with around twelve control
points well distributed over the image. In this step, a new file
mapset/group/name_of_group/CONTROL_POINTS is created, containing a list of pairs of
coordinates of ground control points in photo and target coordinate systems.
# Ground Control Points File
#
# target location: ETRS_33N
# target mapset: target_mapset
# source target status
# east north height east north height (1=ok, 0=ignore)
#------------------------------ ---------------------- ---------------
98.3679932698 906.327649515 0.0 1.0 5.0 100.0 1
733.293023813 1329.61100321 0.0 2.0 6.0 100.0 1
1292.6317412 1703.76325335 0.0 3.0 7.0 100.0 1
1625.54617472 1368.11694482 0.0 4.0 6.0 100.3 1
3239.82849913 1390.97403968 0.0 7.4 6.0 100.3 1
1570.09788497 2790.06537829 0.0 3.0 11.0 100.0 1
Step 7: Detail of ground control points matching in an oblique image and terrain model

8
Ortho-rectify imagery group: i.ortho.rectify

This step is to be run in the source project.

Step 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 project for each selected imagery group file. You may select either the
current window in the target project or the minimal bounding window for the
ortho-rectified image.
Step 8: Ortho-rectified oblique image As a result, the ortho-rectified raster map is
available for visualization and further image analysis.

REFERENCES

       Wolf  P.R.  (1983).  Elements  of Photogrammetry: With Air Photo Interpretation and Remote
       Sensing McGraw Hill Higher Education ISBN-10: 0070713456, ISBN-13: 978-0070713451

AUTHORS

       Mike Baba,  DBA Systems, Inc.
       GRASS development team, 199?-2017

SOURCE CODE

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

       Accessed: Thursday Aug 01 11:31:42 2024

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       © 2003-2024 GRASS Development Team, GRASS GIS 8.4.0 Reference Manual

NAME

KEYWORDS

SYNOPSIS

DESCRIPTION

EXAMPLE

REFERENCES

SEE ALSO

AUTHORS

SOURCE CODE