Digital geological mapping at the British Geological Survey : the “Sigma Mobile” system

Since about 2000, a team at the British Geological Survey (BGS) has developed a digital geological mapping system, called “SIGMA mobile”. The system comes as an add-on to ARC-GIS software and uses a customised MS Access database. It is simple to use, intuitive and only requires fairly basic ARCGIS and MS Access skills. The current version runs with ARC-GIS versions 9.2 to 10. At BGS, SIGMA mobile is run in the field on a physically robust, watertight Xplore tablet computer with a 10.4” screen, 1.2 GHz processor and a 40 Gb hard drive. The computer has a built-in GPS which continuously tracks and updates its position and shows the current location on the screen, superimposed on whatever data layer is visible (e.g. topographic map, historic geological map, satellite image etc). The computer comes with a small USB mouse and keyboard, but in the field a digital touch-screen stylus is used for data entry. Text can be entered freehand (intelligent handwriting recognition), or by touching a virtual on-screen keyboard. An open-source version of SIGMA mobile is available for download free from the BGS website (www.bgs.ac.uk