Computers & Geosciences 30 (2004) 553–558 Short Note g log4PDA: an application for continuous monitoring of gravity using LaCoste&Romberg Aliod 100 systems and Palm OS s run hand-held computers $ Joachim Gottsmann a,b, *, Nicolas Fournier a , Hazel Rymer a a Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK b Institute of Earth Sciences ‘‘Jaume Almera’’, CSIC, Llu ! ısSole´ ! ı Sabar ! ıs s/n, Barcelona 08028, Spain Received 13 February 2003; received in revised form 19 February 2004; accepted 12 March 2004 1. Introduction Micro-gravity surveys are a widely applied geophysi- cal technique to quantify time-dependent sub-surface mass and/or density changes. Applications include for example environmental studies and natural resource exploration (e.g., Murty and Raghavan, 2002) as well as the monitoring of active volcanoes (e.g., Rymer, 1994). Surveys are typically repeated at intervals of several days, weeks or years. Limitations to more frequent readings are predominantly financial, including the cost of instrumentation but more importantly the costs for trained personnel to operate the gravity meters and perform the readings. Not only to cut down the latter but also to limit exposure of gravity-meter operators to hazardous conditions found at active volcanoes, auto- mated reading appears to be a sensible approach. In addition, it has become obvious particularly in the field of volcanology that continuous micro-gravity monitor- ing may provide valuable insights into sub-surface processes governing active volcanism (e.g., Budetta et al., 1999; Gottsmann et al., 2003; Carbone et al., 2003). Thus it has become desirable to resolve gravity changes at a significantly higher frequency (between one reading every 10 s to two readings per day) than practically attainable during conventional surveys using discrete measurements. An automated reading and storing procedure at defined time marks would provide a straightforward solution for continuous monitoring of gravity changes. Towards this end we have developed the software presented here. 2. Gravity-meter hardware The gravity-meter manufacturer LaCoste&Romberg Inc. offers gravity meters equipped with an auto- matic beam nulling system (Aliod 100) 1 that streams relative gravity readings at a frequency of 2 Hz in ASCII code via an external RS-232 port. The data stream may be accessed using computers capable of serial port communication. LaCoste&Romberg Inc. provide soft- ware, which enables the user to perform discrete readings directly onto a Palm OS s run hand-held computer. The software presented here has been designed specifically to continuously read and store gravity data streamed from LaCoste&Romberg gravity meters equipped with the Aliod 100 system onto handheld computers, without the need for a person to be present to manually execute data readings onto the computer. ARTICLE IN PRESS $ Code available from Server at http://www.iamg.org/CGE- ditor/index.htm. *Corresponding author. Institute of Earth Sciences, ‘‘Jaume Almera’’, CSIC, Llu! ıs Sole´ ! ı Sabar ! ıs s/n, Barcelona 08028, Spain. Tel.: +34-93-409-54-10; fax: +34-93-411-00-12. E-mail address: jgottsmann@ija.csic.es (J. Gottsmann). 1 LaCoste&Romberg, Inc. http://www.lacosteromberg.com/ metermanuals.htm. 0098-3004/$ - see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.cageo.2004.03.002