14.05.2007
With the new Gravity Information System, a novel information platform is presented on the web pages of PTB. On this platform, users from metrology can inform themselves about the local intensity of the earth’s field of gravity, related to the place of use. A four-stage gravity data model, mainly composed of freely available secondary (i.e. derived) gravitational field quantities, serves as a data base.
SIS has been developed by PTB as an interactive internet portal which allows to an extended circle of users in physics and industry to get gravity data for every place on the earth.
On the basis of a global geo-potential model which ensures global coverage, regionally higher dissolved data sets are used for compression. A reduction procedure allows local point gravity values to be determined with a relative uncertainty of down to < 10-6 (at least, however, of ~5·10-5), using a height model and a statistic interpolation method. By this, the requirements of a very large part of metrological applications carried out under the influence of the gravitational field are complied with, without local gravimetric measurements being necessary. The graphic surface of the SIS ( Fig. 1) is similar to the route planners known from the Internet, with a data entering part and an information part on the left side and an interactive map on the right side. With the aid of the map control elements, and using a global atlas data bank as the basis for map representation, navigation to nearly any place on earth becomes possible. The issuing of a location-dependent gravity value (acceleration due to gravity) or a gravity anomaly is achieved by entering a place name or the position coordinates (longitude, latitude, altitude), or by clicking into the map with the mouse.
In weighing technology, it is of advantage to have a spatially extended validity range defined for the gravity value at the place of installation which is used for the calibration. This range, the so-called gravity zone, can be calculated with the aid of the SIS as a function of the weighing instrument type to be used, and represented in a pre-selected map section. In addition, further thematic representations of the field of gravity can be viewed as graduated coloured pictures in combination with explanatory isolines in the map section.
The SIS can be found on PTB’s web pages under: Division 1 / Department 1.1 / Gravity-Information-System (SIS)
Figure 1: View of the SIS (example)
Contact person:
Andreas Lindau, Dr. Panagiotis Zervos, FB 1.1, e-mail: Andreas.Lindau@ptb.de, Panagiotis.Zervos@ptb.de