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Aerial Triangulation Bundle Block Adjustment |
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Aerial Triangulation Bundle Block Adjustment |
Aerial Triangulation by Bundle Block adjustment requites a known camera focal length, a set of measured photo coordinates, and a set of ground control points. The following are some of the beauty of Aerial Triangulation by bundle block adjustment in Noobeed, that might be hard to find in other programs.
Each individual image can have a different value of focal length. Just put it next to the photo number. If not given, a default focal length is provided.
It is very easy to assign a weight to an observation, either photo coordinate or ground control coordinates, by adding a standard deviation next to the point. Points without a standard deviation will be assign a default value, which can be as well specified by the user.
To reject any observation, just put a slash, "/" , in front of that line. In fact, the slash sign turns that line to a comment line. Thus, comment lines in an observation file is possible by this technique.
No approximation of parameters are required from the user.
Data and Output
The photo coordinates measurement data are in this file, "obs_xpyp.txt".
The ground control coordinates data are in this file, "obs_gcp.txt".
These are really all you need. Now it's time to do data processing.
It is always possible to type interactively on the screen. However, writing a program is also a good choice, like this.
set path "c:\WHEREVER_YOUR_DATA_ARE"
Blk = AT_BD()
/ this is camera focal length
Blk.focal() = 76.20
/ this is default values of SD (image rectangular coordinates)
Blk.sd_xpyp() = 0.030
/ this is the max no of iterations
Blk.no_iterate() = 10
Blk.loadobs("obs_xpyp")
Blk.loadgcp("obs_gcp")
Blk.adjust("at_bd_out.rpt")
Type the above program, using a text editor, then save it in a file, e.g. "AT.prg". Then load it, and run it.
->load "AT.prg"
->run
Here is the result, "at_bd_out.txt".
Please be advised that the result of the AT adjustment in the file is not yet the final and it is not the intention of this demonstration to show all the stages throughtout the data cleaning process. However, the reader may recognize that there are already some obseved photo coordinates that are taken out, by turning the data to comment using the slash "/" symbol at the beginning of the line.