Over 61,000 Minnesota Geological Survey gravity station represents more than 40 years of surveying. The 2003 release added over 2000 stations relative to its 1991 predecessor as a result of ongoing project work, along with inclusion of additional archival data. Ongoing augmentation of the database is based on measurements at stations on profiles spaced at 0.25 mile intervals along corridors, to areas where stations are spaced at 0.5 to 1.0 mile intervals, and in some areas 2 miles, along available roads and trails. Most of the new measurements were taken with a Lacoste and Romberg G-320 gravity meter with a stated precision of 0.01 milligal. As a result of various error sources, gravity values are considered precise to +/- 0.10 milligal, although errors up to +/- 0.3 milligal occur locally. A proposal has been prepared for an upgrade of the MGS Gravity Database. The most serious limitation in the gravity data is the precision of station location, which is no better than about 200 meters for most of the data due to rounding upon entry to 0.10 minute of latitude or longitude. In addition, following a major campaign of gravity measurements in the 1950s and 1960s, most of the station IDs that would now be helpful in using and evaluating the data were lost in order to fit data onto punch cards. The proposal therefore outlines a plan to upgrade the database by restoring the location of each station to its original precision, and by re-establishing the link to original field IDs. Please visit the MGS's Geophysics Portal. Additional data recovered from the USGS in Western Lake Superior is not part of the statewide dataset. Link to the site is listed below.
Gravity database
