Ordnance Survey – Great Britain's national mapping agency
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6.1: Data formats (3)
Translators and transfer formats
GIS software is designed to work with data stored in specific proprietary binary data formats. The skill of the software developer is to optimise the system’s performance to include as many functions as possible while remaining fast and robust.
The binary code used to store the data is critical to the performance of the software and GIS vendors guard their binary formats as part of their unique intellectual property.
This means, however, that many different file formats exist. With so many different software products available, each with their own data formats, users of one system may, therefore, find it difficult to swap their information with users of another. In the early days of GIS this was serious; if you used data in one package you could not use the same data in a separate system from a different vendor. More recently it has become standard for GIS software to have import facilities that can open files from a diverse range of formats and store them in the preferred local format.
There has also been an explosion in the development of translator software. Products have been developed to convert geographical data between a whole array of formats. It would be unfair in these pages to highlight a specific translator product in comparison to any other. But it is now possible to convert between practically any of the possible data formats, of which there are over a hundred, in either direction. Type GIS translators into a search engine and see the results.
Most of these formats are binary as in this form data is more closely integrated with the software engineering of the products and can be manipulated more quickly. Codes to work with such data can only be written if you know the binary format. There is a series of more simple ASCII file formats that have been developed to enable easier transfer between systems. The human readable nature of ASCII files means that it is an order of magnitude more straightforward for other developers to write programs that can read these files. The MapInfo MID/MIF format is an example of an ASCII transfer format.
Ordnance Survey has traditionally supplied its vector data in ASCII formats with a relatively simple, documented structure that can easily be understood by developers. Until recently the main formats used have been DXF™ and NTF. NTF is also British Standard BS7567, used for the transfer of geographic data, administered by the British Standards Institution (BSI).