The objective of the Geotechnical Exchange Format -GEF for short- is to store measurement results in such a way that they can be analysed at a later time. Two types of information are needed when a measurement has been carried out and the measurement results are available: firstly, information about the circumstances under which the measurement was performed and how the measurement results are stored, and secondly, the measurement results themselves. This means that in addition to the measurement results themselves, mention must also be made of how a measurement is stored and what the figures in the file represent. As regards organisation, this includes the way in which the measurement is stored (such as binary), the number of columns, and the number of scans. For the interpretation, this can be, for instance, which quantity is listed in a column and in which units. For this purpose, the actual measurement results - the data - are preceded by a header which describes in a readable form (ASCII) how the measurement is composed.
The data are divided into columns and scans. One measured quantity is listed per column, for example during a specified period in the time or during a load. A scan is a snap-shot recording, which comprises a variety of registrations from measurement instruments, for example at a fixed point in time, depth or load. The header has its own organisation. Information is profiled using fixed keywords. A keyword is recognised unequivocally. The sequence of most keywords is not important. A keyword is followed by information (except for the EOH keyword). How the information must be interpreted depends on the keyword. The length of the header is variable. As the header is specified in ASCII, it is always readable, via an editor or a simple viewer, regardless of how the data is stored.
The geotechnical exchange format is a type of control language with words. Keywords can be added, if required. The addition of words has consequences for the software which can import a GEF file: the ability to recognise new words must be added to the software. The information belonging to each keyword has a fixed structure. If a program recognises a keyword then it can import the information belonging to that keyword, as the structure of a keyword’s information is defined unequivocally.
The Geotechnical Exchange Format is the combination of the best items of the Standard File Format (GeoDelft / Deltares) and Gorilla! (A.P. van den Berg). The formal description of the standard file format is laid down in a GeoDelft document, written by dr. H. den Adel and drs.P.E.L. Schaminée. This document originates from their document and has been revised to produce a first formal description of GEF.
