1i.ortho.photo(1) Grass User's Manual i.ortho.photo(1)
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6 i.ortho.photo
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9 i.ortho.photo allows the user to ortho-rectify imagery group files. An
10 imagery group consists of several scanned aerial photographs (raster
11 files) of a common area. Imagery groups can be created or modified
12 using the GRASS Image Processing Program i.group, or using the first
13 menu option described below. i.ortho.photo guides the user through the
14 steps required to ortho-rectify the raster files in a single imagery
15 group.
16 The first menu in i.ortho.photo provides the user with the following
18 options:
19 Initialization Options:
21 1) Select/Modify imagery group
22 2) Select/Modify imagery group target
23 3) Select/Modify target elevation model
24 4) Select/Modify imagery group camera
25 Transformation Parameter Computation:
27 5) Compute image-to-photo transformation parameters
28 6) Initialize exposure station parameters
29 7) Compute photo-to-target transformation parameters
30 Ortho-rectification Option:
32 8) Ortho-rectify imagery group raster files
33 RETURN to exit
35 >
36 To ortho-rectify aerial images the user has to follow the menu options
38 step by step. Generally the user builds a target location containing a
39 projected DEM and a map reference (topo sheet or other map). Another
40 xy-location will contain the aerial photo. The entire rectification
41 process is started within the xy-location. First the target to the pro‐
42 jected location has to be set (i.target), then the image references
43 (fiducial points) will be defined. After describing the camera parame‐
44 ters, reference points from aerial image to the topo sheet from the
45 target location will be set. The local elevation will be taken from the
46 target DEM. Finally the aerial image will be rectified.
47 The options to follow are described as follows:
49 1. Select/Modify imagery group
51 The current imagery group is display at the top of the previous
52 menu. You may select another (new or existing) imagery group
53 for the ortho-rectification program using option (1). After
54 choosing option (1) you will be prompted for the name of a new
55 or existing imagery group. Option (1) using the GRASS Image
56 Processing Program i.group, for creation or modification of
57 imagery groups. For more information on imagery group creation
58 or modification please the the GRASS manual page for i.group.
59 2. Select/Modify imagery group target
61 The target location and mapset may be selected or modified using
62 option (2). After choosing option (2) you will be prompted for
63 the names of the target location and mapset, where the ortho-
64 rectified raster files will reside. The target location is also
65 the location from which the elevation model (raster file) will
66 be selected -- see option (3). Option (2) uses the GRASS Image
67 Processing Program i.target, for selection or modification of
68 the imagery group target location and mapset. For more informa‐
69 tion on imagery group selection or modification please the the
70 GRASS manual page for i.target.
71 3. Select/Modify target elevation model
73 Option (3) allows you to select the raster file from the target
74 location to be used as the elevation model. The elevation model
75 is required for both the computation of photo-to-target parame‐
76 ters (option 6) and for the ortho-rectification of the imagery
77 group files (option 8). The raster file select for the eleva‐
78 tion model should cover the entire area of the image group to be
79 ortho-rectified. Currently, the elevation model raster file is
80 expected to be in units of meters. DTED and DEM files are suit‐
81 able for use as the elevation model in the ortho-rectification
82 program. After selection option (3) you will be prompted for
83 the name of the raster file in the target location that you want
84 to use as the elevation model.
85 4. Select/Modify imagery group camera
87 Using option (4) you may select or create an camera reference
88 file that will be used with the current imagery group. A camera
89 reference file contains information on the internal characteris‐
90 tics of the aerial camera, as well as the geometry of the fidu‐
91 cial or reseau marks. The most important characteristic of the
92 camera is its focal length. Fiducial or reseau marks locations
93 are required to compute the scanned image to photo-coordinate
94 transformation parameter (option 5). For a more detailed
95 description of option (4) please see the GRASS manual page for
96 photo.camera.
97 5. Compute image-to-photo transformation parameters
99 The scanned image to photo-coordinate transformation parameters
100 are computed using option (5). In this interactive option you
101 associate scanned reference points (fiducials, reseau marks,
102 etc.) with their known photo coordinates from the camera refer‐
103 ence file. Complete documentation for this option is available
104 under the manual entry photo.2image.
105 6. Initialize exposure station parameters
107 If option (6) is selected, initial camera exposure station
108 parameters and initial variances may be selected or modified.
109 Complete documentation for this option is available under the
110 manual entry photo.init.
111 7. Compute photo-to-target transformation parameters
113 The photo to target transformation parameters are compute using
114 option (7). Here control points are marked on one or more
115 imagery group files and associated with there known standard
116 (e.g. UTM) and elevation coordinates. Complete documentation
117 for this option is available under the manual entry photo.2tar‐
118 get.
119 8. Ortho-photo imagery group files
121 Option (8) is used to perform the actual image ortho-rectifica‐
122 tion after all of the transformation parameters have been com‐
123 puted. Ortho-rectified raster files will be created in the tar‐
124 get location for each selected imagery group file. You may
125 select either the current window in the target location or the
126 minimal bounding window for the ortho-rectified image. Complete
127 documentation for this option is available under the manual
128 entry photo.rectify.
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131 i.ortho.photo currently requires the elevation model to be in meters,
132 and the target location to be a standard (e.g. UTM) coordinate system.
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135 photo.camera, photo.2image, photo.2target, photo.init, photo.rectify
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138 Mike Baba, DBA Systems, Inc.
139 Updated rectification and elevation map to FP 1/2002 Markus Neteler
141 Last changed: $Date: 2005/11/15 08:14:53 $
143GRASS 6.2.2 i.ortho.photo(1)