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The Geomar Multi31 system consists of two programs: field data acquisition component (ML31) and the Windows (98/2K/XP) based data processing software (Multi31). The program ML31 is designed for Allegro field computer, although, if necessary it can be used with any other IBM compatible computer running an MS DOS operating system and equipped with adequate number of serial ports.

The program is used as a data acquisition system for Geonics EM31-3, which employs array of three EM31s with varying transmitter and receiver separations. The ML31 is capable of recording output from up to 5 EM31 in case such system will be assembled.

Multi31 software works with virtually any GPS receiver by supporting NMEA messages: GGA, POS, GLL, LLQ, LLK, GGK, and Leica Robotics Total Station TPS1100, and collects up to 5 EM31s and GPS data into one file simultaneously.

The data acquisition program can process, display, and record 30 readings per second. Readings are displayed in real time as values in mS/m and ppt as well as in graphic mode. Two bars, for Conductivity and Inphase represent the output of each instrument. This allows for very fast visual information about each EM31 output. The ML31 also continuously monitors the dipole mode and range for each instrument. Current Latitude/Longitude and GPS signal quality parameters are displayed as well.

The program Multi31 is designed to process data collected under the control of program ML31. Main function this program is to position each EM31 antenna based on recorded GPS positions, the configuration of the system (GPS antenna offsets for each unit), and several user specified filters. The Multi31 also allows you to correct the collected GPS positions with post-processed GPS files.

In addition to acquiring EM31 data the system will convert any Field PC to a stand-alone logger for GPS/DGPS data collection, taking away the need to purchase additional more expensive GPS components.