2.0 Preparation of the GIANT Input Data Stream

Even an informal understanding of photogrammetric triangulation would lead one to anticipate the general data requirements for GIANT. Measurements of control, pass, and tie points on a frame, supplemented by some indexing information, comprise the image file. The coordinates of the control points that permit the absolute orientation, sometimes referred to as the geo-registration, comprise the control file. Information, however approximate, about the locations of the exposure stations forms the frame file. The frame file can exist in either of two forms and the user is urged to read Section 2.1.2 carefully to understand the special circumstances surrounding the frame file.

GIANT uses other files for its work, and a directory listing of a project will be likely to show more than the three files mentioned so far. These additional files, however, are created under program control and require no formal intervention on the part of the user. In fact, the user is cautioned against modifying the automatically-generated files with a text editor: their modification can--and should--be achieved through appropriate forms of the Graphical User Interface. The image, control and frame files are the minimal subset required for a GIANT project to be recognized by the system. If any of these three are not present, GIANT will not recognize the project.

The three required files are fixed-format, ASCII files. They may be created in a manner that is most convenient for the user. The image file contains the coordinates of all of the measured images, and is probably best formed under the control of the program that guides the actual collection of the triangulation data. If the data collection program cannot be modified to output data in the appropriate format, a second, off-line program could be used to re-format the data from its original, proprietary format into the format required by GIANT, along with the addition of other required indexing data. If a re-formatting package cannot be written, it is entirely possible to manually build the image file with a standard DOS text editing utility program. In addition to being tedious, this final option is also, obviously, the more prone to errors. The same remarks apply to the construction of the control and frame files, although these programs would not typically be formed by any type of automated process. Regardless of their method of creation, GIANT provides numerous data file integrity checking facilities, described later in the chapter.


For both input and output, GIANT uses a compressed format to specify an angle in degrees, minutes and seconds. The format is illustrated by two examples.

15E30'35.468" is written 153035.468

-1760209.928 represents -176E 2' 9.928"


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