A computer system for the storage and retrieval of gravity data, Kingdom of Saudi Arabia

Abstract

A computer system has been developed for the systematic storage and retrieval of data. All pertinent facts relating to station measurements and computed Bouguer values may be retrieved either by project name or by geographical coordinates. Features of the system include visual display in the form of printer listings of and printer plots of station locations. The retrieved format interfaces with the format of GEOPAC, a system of computer programs designed for the analysis of geophysical data. INTRODUCTION For the past several years high speed digital computers have provided a convenient and rapid means to systematically store large volumes of information and to retrieve selected items by various criteria. In this particular application a system of storing measurements has been devised enabling the interested investigator to recall all or any part of the stored data. The initiation of such a system in Saudi Arabia is needed because the rate of collection is increasing and the problems of inventory and accessibility will increase. Creation of a central bank permits systematic storage while making the information readily available to interested parties. Each value consists of a number of related measurements usually referred to as gravity facts. These include time of measurement, geographical coordinates and elevation of the station, and the computed Bouguer anomaly. Entry to the storage bank is by punched cards which are then stored on a magnetic device. The computer lists the stored and provides a plot of station locations. Stored can be retrieved by either project name or by geographical coordinates. The computer provides a visual display in the form of a list of the retrieved and a plot of station locations. An important feature of the retrieval is the simultaneous creation of a magnetic tape (or disk) file containing the in a form acceptable for entry into GEOPAC, a system of computer programs designed for the analysis of geophysical (Godson, 1973). The system was developed as part of the work agreement between the U. S. Geological Survey and the Ministry of Petroleum and Mineral Resources, Kingdom of Saudi Arabia. It was tested, is operational, and is on file at the IBM 370/145 computer at the Computer Center, College of Petroleum and Minerals, Dhahran. DESCRIPTION Gravity station are stored as a file on a magnetic device. Data for each station or stations are assigned a project name and any number of projects can be stored in the same file. Each project, however, must be assigned a different name, so that each is uniquely identified within the file. Data input consists of a parameter card to initiate execution, an identification card containing the project name and a of station cards, altogether called a data set A description of the information contained on the input cards and their associated formats is explained -below in Data Input. If more than one project is to be stored on a particular tape or disk file, a new identification card and associated station cards must be included. This procedure is repeated until all projects have been stored (see figure 1 for generalized chart of flow). The is stored on a magnetic device in an unformatted form using Fortran reference number 12 (FT12F001). The first record contains the project name and the number of stations in the project. The following records contain station data/ one record for each of the stations (Appendix 1: Gravity storage format). As the station are placed on a storage device, it is printed (fig. 2), and stored in the computer. At the same time the maximum and minimum latitude and longitude is calculated for each set. After storage of a is complete, the geodetic position of each station is computed, using a Lambert conformal conic map projection, and converted to X,Y coordinates. The Y-axis is the median longitude of the as determined from the minimum and maximum longitude values and the X-axis is the equator. When all the station locations have been converted, a position plot is produced on the printer (fig. 3). This plot serves as a visual check for erroneous locations in the input data. It also provides a convenient means for determining optimum dimensions for the orthogonal grid transformation. At the conclusion of the printer plot, the is output on a temporary disk file in case additional processing may be required. The format is compatible with the requirements for input to the