Gravity measurements in the Moscow gravity network I. A. Oshchepkov1,3, R. A. Sermyagin1, A. A. Spesivtsev1, V. D. Yushkin1, A. V. Pozdnyakov1, A. A. Kovrov2, P. A. Yuzefovich2,4 1Center of Geodesy, Cartography and SDI (ex. TsNIIGAiK) 2Moscow State University of Geodesy and Cartography (MIIGAiK) 3ilya@geod.ru, 4pauzhas@gmail.com Introduction The metrological local precise gravity networks are created to calibrate relative gravimeters, to test absolute gravimeters (AG) and to improve methods of performing and processing gravity measurements. We report on the gravity measurements campaign in the Moscow Gravity Network in Spring 2015. The major goals of this campaign were to determine: • linear scale-factors for relative gravimeters, • gravity at all stations w.r.t. International Comparisons of Absolute Gravimeters (ICAG2013), • oﬀsets of the AG which did not participate in Russian–Finnish Comparisons of Absolute Gravimeters (RFCAG2013). 1. Network The Moscow Gravity Network consists of six stations (see Fig.1): TsNIIAGik, Zvenigorod, Krasnaya Pres- nya, Ledovo, Troitse Seltso, Mendeleevo. The largest gravity diﬀerence is about 52 mGal. All stations are permanent and have gravity values from absolute measurements which are usually repeated annualy. 46 −6 1 20 27 −52 −19 −7 −19 −7 TsNIIGAiK Troitse−Seltso Krasnaya Presnya Mendeleevo Zvenigorod Ledovo 20 km Figure 1: Moscow gravity network The absolute gravity measurements at TsNIIGAiK and Zvenigorod were performed by FG5x #221 (Finnish Geospatial Research Institute) in 2013 and gravity values there are known w.r.t. ICAG2013 in Walferdange (Luxembourg). The relative gravity measurements were planned so that each point was connected to the nearest three neighbors. There are 10 lines in the network. 2. Instruments and measurements Figure 2: All CG-5 gravimeters (left) and absolute gravimeter GBL-M (right) 2.1 Absolute gravity measurements The absolute gravity measurements were made with GBL-M #001 and #003 ﬁeld ballistic gravimeters[3] (see Fig.2). Both gravimeters did not participate in RFCAG2013 and have no correction w.r.t. ICAG2013. The measurements were performed at three points with each gravimeter with overlaps (see table below). S/N Stations GBL–M #001 TsNIIGAiK, Krasnaya Presnya, Mendeleevo GBL–M #003 TsNIIGAiK, Krasnaya Presnya, Ledovo All processing methods of the absolute gravity measurements were standard, except: • no self–attraction and diﬀraction corrections were applied, • Atlantida3.1 2014[2] was used to calculate tide correction. 2.2 Relative gravity measurements The relative gravity measurements campaign with the ﬁve Scintrex CG–5 • #41262, 41265, 40443 (of TsNIIGAiK) and • #41077, 4173 (of MIIGAiK) spring gravimeters took place in March–May 2015 at all stations of the network for the ﬁrst time. Here are some highlights: • diﬀerence method (from two to four runs per line); • 30 – 60 minutes of measurements per station, • thus no more than one line per day; • very careful transportation in the hands of the operators to minimize the errors due to tilts, shocks, weather conditions etc.; 3. Data processing All measurements were processed and adjusted with the newly and actively developed gravity processing software (not public yet) in Python programming language. 3.1 Vertical gravity gradients The gravity changes above the mark were approximated by second degree polynomial (see Table. 2) as discussed in [1], unadjusted measurements at three or four vertical levels were used as input data. Table 2: Polynomial approximation results: a and σa in µGal, b and σb in µGal m−1 Station a b σa σb σab TsNIIGAiK -349.59 15.59 3.50 2.48 -8.49 Zvenigorod -321.86 4.00 4.20 2.93 -12.13 Krasnaya Presnya -297.49 3.34 6.03 4.20 -24.82 Ledovo -320.91 7.83 6.06 4.29 -25.50 Troitse-Seltso -355.84 12.44 4.89 3.27 -15.56 Mendeleevo -255.04 -3.43 8.69 5.41 -46.24 3.2 Network adjustment The least–squares adjustment solutions were computed for three main cases: 1. RG+ICAG2013: relative measurem