The Text to DTI Translation.

The translation of text file to DTI is defined primarily by specifying an index file via the /INDEX = index-file-spec qualifier. The index file is a single line ASCII file providing, in order, the DTI x,y origin, the x,y DTI extents (number of pixels) and the x,y DTI pixel sizes.

The input text data is read and the contents written to the DTI file in the standard DTI order, ie. starting at the SW corner and proceeding in a clockwise direction (in the increasing y direction, repeated for successive columns). The qualifiers /BYTE, /LONG, /REAL or /WORD may be used to set up a different output data format, the default being to output word data.

The qualifiers /CLOCKWISE, /ANTICLOCKWISE, /SW, /SE, /NW or /NE may be used to set the DTI header to the correct values if this default setup is not a suitable representation for the subsequent use of the DTI file.

The text data may be simple free format z values, or x,y,z value records on separate lines, this latter option being selected with the /XYZ qualifier. The default is to read just z height values. (The text data may represent height (z), or any other numeric attribute such as vegetation type, slope, clutter category, colour etc. For simplicity in this document it is referred to as z.)

The DTI Projection Record.

DTI files output from DTIFROMTEXT are created with an 'LSLA' (LSL type A) header with a DTI Projection record. The Projection record contains unset projection and spheroid codes and associated parameters.

The coordinates of address (1,1) of the matrix are taken from the /INDEX file (or the first x,y,z record) and written to the DTI header and projection origin offset fields.

The MATRIX utilities DTIPATCH or DTITRANS/DESCRIPTOR may be used to change the output DTI file header entries as an alternative to using the relevant qualifiers when running DTIFROMTEXT.

The Pre-defined Customer Formats.

At present there are two supported pre-defined formats that may be read by DTIFROMTEXT specified by the /CUSTOMER = customer-name qualifier. These customer-names are AUSLIG (to translate AUSMAP data from the Australian Surveying and Land Information Group) and MOBILE (to translate data from Mobile Systems UK Ltd.).

The first format (AUSLIG) expects an ASCII file of x,y,z values with one coordinate triple per line starting at the SW corner and increasing in longitude for a particular latitude value, followed by the next latitude valueS moving up the file. These x,y coordinate values represent the positions in degrees in the order lat, long with positive latitude values down from the equator, resulting in a DTI corner and direction of SW and anticlockwise. The index qualifier is not required as the origin offset is contained in the first data record, and the DTI extents and pixel sizes are known to the program (ie. 101 x 101 values of 0.005 degree size pixels on a geographic projection).

The second format (MOBILE) uses a binary file containing just the height values representing a DTI file with order and direction of NW and clockwise. Again the index file is not required except to give the origin offset as the DTI extents and pixel sizes are known to the program (ie. 320 x 320 values of 1.0 degree x 40 minute size pixels on a geographic projection).


See dtifromtextmsg.html generated from DTIFROMTEXTMSG.RNO.

See appendix.html generated from APPENDIX.RNO.