Text Format Description |
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STRUCTURE OF THE FORMAT IN TEXT (SYMBOLIC) REPRESENTATION The SXF format allows recording digital vector terrain data as a text file. This capability is intended to ensure the data exchange process between systems of different purposes operating on different hardware and software platforms.
GENERAL VIEW OF THE SXF FORMAT TEXT FILE The SXF format can have a textual representation as a file with the following structure: .SXF format_revision P001 nomenclature ... P101 B L of the southwestern corner P102 B L of the northwestern corner ... P207 scale_denominator ... .DAT number_of_map_objects .OBJ object_code localization_character .KEY object_own_number .GEN lower_visibility_bound upper_visibility_bound .GRP object_group_number .MET number_of_subobjects number_of_object_points x y H or B L H (depending on the coordinate system) ... number_of_subobject_points (if number_of_subobjects > 0) x y H or B L H ... .SEM number_of_characteristics characteristic_code characteristic_value ... .OBJ object_code localization_character ... .END
A text file in SXF format consists of a set of variable-length strings in ASCII codes. Strings must end with the control codes «\x0DOA». A period symbol may appear at the beginning of a line, followed by a keyword (SXF, DAT, OBJ, KEY, GEN, MET, SEM, END, etc.) or the values of the corresponding data fields about the sheet or object. The presence of empty lines containing spaces and end-of-line characters, and comment lines starting with the "//" symbol is allowed. Lines with the keywords SXF, DAT, OBJ, END are mandatory.
The first line of the text file must contain the keyword SXF and the format revision (e.g., "3.0"), separated by a space (spaces). Passport data about the sheet must be at the beginning of the file, followed by object data. The passport data section is optional and may be absent. The description of map objects begins with a line containing the keyword DAT and the number of objects, separated by a space (spaces). This line is mandatory. The description of a single object begins with a line containing the keyword OBJ, the object classification code, and the localization character, separated by spaces. The sign of completion of the digital data set about a terrain area (sheet) is a line with the keyword END.
The minimum correct content of a text file in SXF format is as follows: .SXF 3.0 .DAT 1 .OBJ 1 LIN 1 0 0 .END
If passport data is absent, it is assumed that the object geometry is specified in a rectangular local coordinate system in meters.
The dimensionality of the coordinate system (two- or three-dimensional) and the format of coordinate representation (integer, fixed point, etc.) can be arbitrary and are determined during data processing. |
