Laser-Scan Ltd.

Software Product Specification


(Laser-Scan Mapping Kernel Package)

For LAMPS V4.3 - 25-Feb-1994
Copyright (C) $$year Laser-Scan Ltd
Science Park, Milton Road, Cambridge, England CB4 4FY  tel: (0223) 420414
Document "MAPPING SPS"    Category "SALES - Spec"
Document Issue 1.0 Paul Hardy   2-Feb-1987
Document Issue 1.1 Paul Hardy   7-Apr-1987
Document Issue 1.2 Clarke Brunt   5-May-1992
Document Issue 2.0 Paul Hardy   25-Feb-1994



The Laser-Scan IFF Mapping Kernel package (MAPPING) provides basic support and interface libraries for the applications packages that make up the Laser-Scan Automated Map Production System (LAMPS).

It is recommended that the reader becomes familiar with the LAMPS Environment Guide which outlines in some detail the hardware and software environment required by the LAMPS package as a whole (of which MAPPING is the kernel).

IFF stands for &Internal &Feature &Format and is the Laser-Scan vector file format generated by VTRAK and other Laser-Scan mapping systems and used as the data structure throughout the Laser-Scan LAMPS system. IFF files are binary and cannot be manipulated directly using a text editor. The MAPPING package provides two interface libraries, IFFLIB to allow customers to write programs to read and write IFF files, and FRTLIB to look up the representational attributes of IFF features in Feature Representation Tables.


The following facilities are included in the MAPPING package software. Further details can be found in the IFF User Guide, the IFFLIB Reference Manual, the FRT User Guide, and the FRTLIB Reference Manual, but the presence or absence of a facility in such a manual does not imply any commitment by Laser-Scan.



LSL IFF files are word-addressed direct-access binary files, with a variable length record mechanism (Entries) superimposed. Coordinates within IFF are held in ST, ZS or CB entries, depending on whether they are 2D, 3D, or multi-dimensional points. Regardless of entry type, coordinates are held as 32-bit (single precision) floating point binary numbers. This gives them a range of 10**38 to 10**-38, and between 7 and 8 significant figures.

All coordinates in a file are assumed by the software to be relative to a local origin, the value of which is held in a Map Descriptor at the start of the file, as a pair of 64-bit (double-precision) floating point binary numbers. This gives a range of 10**38 to 10**-38, and between 15 and 16 significant figures. It is not necessary that this local origin should be one of the corners or the middle of the area, merely that it should lie reasonably close to the area. Conventionally, it is often set so that the bottom left corner of the sheet lies at (0,0), but it is quite acceptable for several files to share the same origin offset, eg of the current UTM zone "brick".


One of the main advantages of coordinate storage as floating point rather than integer numbers, is that IFF files are largely independent of the units of the data stored in them. Map data is often stored with ground metres as the unit, but IFF data can and does handle units as distinct as lat/long degrees, seconds of arc, feet, miles, nautical miles, sheet mm, sheet thou.


A DEC 32-bit (single precision) floating point binary number has 1 sign bit, 8 exponent bits, and a 23 bit mantissa. Because the value is always normalised, the first mantissa bit which would always be a 1 is assumed, giving an effective mantissa of 24 bits. This gives a precision of approximately 1 part in 2**23, allowing 33,554,433 positive values, doubled to 67,108,865 if negative values are used.

The 64-bit double precision origin offset has the same structure, but has a 55 bit mantissa, allowing more than 1,000,000,000,000,000 distinct values.

The combination of the single precision coordinate with the double precision offset allows us to store coordinates in a uniform space, which can typically cover the whole earth to a ground precision of much better than 1mm in typical sized IFF files.




OpenVMS VAX Version 5.5-2, or OpenVMS AXP V1.5 (or higher version, assuming continued upwards compatability by DEC) concurrently with other interactive and batch processes.

Laser-Scan's LITES2 interactive digitising and editing software running on the same host computer is recommended for digitising and editing vector input data. VTRAK automated digitising is recommended for volume input of documents. The PLOTTING package (FPP program) is recomended both for check plotting and for high quality photoplotting.

The MAPPING package, and the IMP (IFF Map Processing) utility package are software prerequisites for LITES2, VTRAK, PLOTTING, and any other LAMPS software.

It is recommended that the reader becomes familiar with the LAMPS Environment Guide which outlines in greater detail the hardware and software environment required by the LAMPS package as a whole (of which MAPPING is the kernel).


The minimum hardware and software requirements for any future version of this product may be different from the minimum requirements for the current version.


MAPPING is a fully supported Laser-Scan standard software product.