1photo.2image(1) Grass User's Manual photo.2image(1)
2
6 photo.2image
7
9 photo.2image is an imagery function that enables you to mark fiducial
10 or reseau points on an image to be ortho-rectified and then computes
11 the image-to-photo coordinate transformation parameters. The coordi‐
12 nates of the fiducials or reseau marks can be choosen for a camera ref‐
13 erence file.
14 During the process of marking reference points with known photo coordi‐
16 nates, you may compute the RMS (root mean square) error for each refer‐
17 ence point entered. photo.2image does this by calculating the trans‐
18 formation equation (the same one that is calculated by i.points ), and
19 then plugging these results into an equation for RMS error.
20 photo.2image offers a zoom option to locate precisely the fiducial or
22 reseau point to be marked on an image.
23 To run photo.2image, a graphics monitor is required.
25 The procedure for marking fiducial or reseau points, entering known
27 photo-coordinates, and analyzing the RMS error is described below.
28 The terminal screen displays this message:
30 use mouse now...
32 The graphics monitor displays the following screen:
34 +---------------------------+---------------------------------+
35 |imagery | |
36 +---------------------------+---------------------------------+
37 | | |
38 | | |
39 | | |
40 | | |
41 | | |
42 | | |
43 | | |
44 +---------------------------+---------------------------------+
45 | | |
46 | | |
47 | | |
48 | | |
49 | | |
50 | | |
51 | | |
52 +---------------------------+---------------------------------+
53 | | |
54 +---------------------------+---------------------------------+
55 A pop-down menu like that shown below will be superimposed on the left
58 half of the screen:
59 +------------------------------------------+
62 | Double click on raster map to be plotted |
63 | Double click here to cancel |
64 +------------------------------------------+
65 +----------------+
66 |Mapset imagery |
67 +-------+--------+
68 |gs13.1 | gs21.1 |
69 +-------+--------+
70 |gs14.1 | gs22.2 |
71 +-------+--------+
72 Any single file in the imagery group may be used on which to mark
73 points, and you may mark points on more than one file in the imagery
74 group to accumulate the suggested minimum number of 4-8 fiducial or
75 ressue points. The imagery file selected is displayed in the upper
76 left quadrant of the screen.
77
79 The camera reference file may be viewed by placing the mouse cross
80 hairs on the words CAMERA. The camera reference file will be displayed
81 in the lower left quadrant of the display:
82 |---------------------------------------------------------------|
85 |Camera Reference File |
86 |---------------------------------------------------------------|
87 | CAMERA NAME : camera name |
88 | CAMERA ID : L1234 |
89 | CAMERA CFL : 153.021 mm. |
90 | CAMERA XP : 0.050 mm. |
91 | CAMERA XP : 0.056 mm. |
92 | number of fid. 4 |
93 |---------------------------------------------------------------|
94 | |
95 |ID (X PHOTO) mm. (Y PHOTO) mm. |
96 |_______________________________________________________________|
97 |1 -105.023 110.123 |
98 |2 107.987 109.834 |
99 |3 110.965 -104.329 |
100 |4 -103.932 -110.352 |
101 |_______________________________________________________________|
102 The following menu is displayed at the bottom of the graphics display:
105 +-----+------+-----------+--------+---------+-------------------+-------------+
108 |Quit | Zoom | Plot Cell | Camera | Analyze | Input->KEYBOARD | CAM‐
109 ERA FILE |
110 +-----+------+-----------+--------+---------+-------------------+-------------+
111
114 To magnify the displayed file, you must place the mouse cross hairs on
115 the word ZOOM. The following menu will then be displayed at the bottom
116 of the screen:
117 +-------+-----+-------++--------------------+
120 |Cancel | Box | Point ||Select type of ZOOM |
121 +-------+-----+-------++--------------------+
122 You have the option of identifying the zoom window either by using the
125 mouse to make a box, or by using the mouse to mark the center of the
126 desired window, and adjusting the magnification factor. The terminal
127 screen will display a mouse button menu to guide you in identifying the
128 window. The section of the image within the zoom window will be dis‐
129 played in the upper right hand quadrant.
130
132 To mark the known reference points (fiducial marks, reseau marks, etc.)
133 on the image, you must place the mouse cross hairs on the corresponding
134 location on the image to be marked and press the left hand button on
135 the mouse. A diamond shaped symbol will be marked on the image.
136 If you wish to use the camera reference file only as a comparative
138 reference, then the keyboard can be chosen as the means to input photo
139 coordinates corresponding to the marked reference points on the image.
140 This is done by placing the mouse cross hairs on the word KEYBOARD and
141 pressing the left button on the mouse.
142 The following menu is displayed on the graphics terminal:
144 +------------------------------------+--------------------------+
147 |Point 1 marked at IMAGE COORDINATES | |
148 |east: 1023.77 | |
149 |north: 506.56 | |
150 | | |
151 | | |
152 | | |
153 | | |
154 | | |
155 +------------------------------------+--------------------------+
156 |Enter PHOTO COORDINATES as x and y: |
157 +---------------------------------------------------------------+
158 You then enter the known (x,y) photo coordinates, relative to the per‐
161 spective center, for the reference point marked on the image. If you
162 do not wish to enter a coordinate, simply hit RETURN to continue; the
163 marked reference point will disappear.
164 If you select the CAMERA FILE option, then reference points marked on
166 the image will be associated with selected photo coordinates from the
167 displayed camera reference file. In this option, when you mark a point
168 on the image, the following menu is displayed on the graphics terminal:
169 -------------------------------------------------------------
172 CANCEL Double click on the fiducial mark to be referenced
173 -------------------------------------------------------------
174 If you would like to select the photo coordinates of a displayed refer‐
177 ence mark, this can be accomplished by placing the mouse cross hairs on
178 the reference point to be selected and pressing the left button on the
179 mouse twice. After a reference point is selected from the display, you
180 are prompted with "Look ok? (Y/N)". If you respond with no, the refer‐
181 ence point is ignored. If you respond with yes, the following is dis‐
182 played on the terminal:
183 +----------------------------------------+--------------------------+
186 |Point 1 marked at IMAGE COORDINATES | |
187 |east: 1023.77 | |
188 |north: 1065.41 | |
189 | | |
190 | | |
191 |Point 1 referenced at PHOTO COORDINATES | |
192 |X: -105.023 | |
193 |Y: 110.122 | |
194 | | |
195 | | |
196 | | |
197 | | |
198 | | |
199 +----------------------------------------+--------------------------+
200 | use mouse now... |
201 +----------------------------------------+--------------------------+
202 The photo coordinates and the corresponding image coordinates are auto‐
205 matically saved in the photo_points file associated with the imagery
206 group.
207
209 After a number of points have been marked (4 to 8), you can check the
210 RMS error of the points marked on the image. This is done by placing
211 the mouse cross hairs on the word ANALYZE at the bottom of the monitor.
212 An error report resembling the one shown below is superimposed on the
213 monitor:
214 +--------------------------------------------------------------------+
217 | error image photo |
218 | |
219 |# row col photo east north x y |
220 |1 0.0 -0.9 1.0 1048.5 -144.8 -105.023 110.122 |
221 |2 0.4 1.0 1.3 2153.1 -567.2 107.987 109.834 |
222 |3 -1.2 -0.5 0.6 1452.8 -476.5 110.965 -104.329 |
223 |4 1.1 0.5 1.3 1034.0 -109.2 -103.932 -110.352 |
224 | |
225 +--------------------------------------------------------------------+
226 | overall rms error: 4.46 |
227 +--------------------------------------------------------------------+
228 The following menu then appears at the bottom of the monitor:
231 +-----+-------+------+-----------------------------------------------+
234 |DONE | PRINT | FILE | Double click on point to be included/excluded |
235 +-----+-------+------+-----------------------------------------------+
236 The RMS error for the image is given under the column TITLEd "error"
239 and subTITLEd "row" and "col". In the above report, point number 1 is
240 0.0 rows and -0.9 columns from the predicted location calculated from
241 the transformation equation. The RMS error for the photo coordinates
242 is listed under the heading "photo". This is the RMS error for the x
243 and y coordinates of the photo coordinates but it is presented in the
244 table using one general value. The overall RMS error is displayed at
245 the bottom of the screen in milimeters. Points that create high RMS
246 error are displayed in red on the monitor (represented here in ital‐
247 ics).
248 The location of the point marked on the imagery group file is given
250 under the heading "image" and the subheadings "east" and "north". The
251 location of the point in the photo coordinates is given under the head‐
252 ing "photo" and the subheadings "x" and "y". If you would like to
253 exclude or include a point, this can be accomplished by placing the
254 mouse cross hairs on the point number to be included (if the point is
255 absent) or excluded (if the point is displayed) and pressing the left
256 button on the mouse twice. When a point is excluded, it is not after‐
257 wards included in the calculation of the RMS error, or included in the
258 final transformation matrix. However, it can be retrieved within
259 photo.2image at any time by double clicking with the mouse as described
260 above.
261
263 To end the photo.2image program place the mouse cross hairs on the word
264 QUIT; the marked reference points (including coordinates) will be
265 saved.
266
268 A good rule of thumb is to mark at least 4 to 8 points which are evenly
269 distributed over the perimeter of the imagery group file in order to
270 obtain an accurate transformation equation for the rectification
271 process. The RMS error may increase with more points added, but the
272 transformation equation will be more accurate.
273 An RMS error of less than or equal to approximately one resolution unit
275 (pixel) for the image being rectified is generally considered accept‐
276 able.
277
279 i.ortho.photo, photo.camera, photo.2target, photo.init, photo.rectify
280
282 Mike Baba, DBA Systems, Inc.
283 Last changed: $Date: 2006-12-15 11:10:21 +0100 (Fri, 15 Dec 2006) $
285GRASS 6.3.0 photo.2image(1)