Jökull - 01.12.1970, Page 42

REDUCTION
OF THE OBSERVATIONS
Drifting in the gravity meter, which can be
in the order of 0.5—1.0 mgal/day, has to be
taken into account and the readings of the
meter corrected. During the survey this correct-
ion had to be estimated from repeated ob-
servations at stations of resting, involving a
timelapse of a few hours to one day and sub-
sequently repeated obervations at a few old
stations on the return journey after a time gap
of one day to one week. Because of the up-
setting of any regular drifting pattern by the
inevitably unsmooth transport this is some-
what unsatisfactory and one can only claim
accuracy in the order of 2.0 mgal on the values
for gobs presented in Table 1. But it should
be kept in mind that due to closeness both in
space and time between individual stations the
relative error over any limited area of 10 stat-
ions, say, is negligible.
The values in the table are based on the
value 982,104.0 mgal at Jökulheimar where the
station was located at the flagpole close to the
hut of the Icelandic Glaciological Society and
981,935.2 mgal at the bench mark on top of
the mountain Kerlingar. Both these values were
obtained during the survey but Pálmason deter-
mined gobs at Jökulheimar to be 982,103.8 mgal
in 1960 (Pálmason, 1964).
All gravity stations coincided with the stat-
ions in the profile survey. Thus the error in
the elevation given in Table 1 may be con-
sidered negligible.
Terrain corrections were computed at all
reference stations. Cylindrical zone charts were
TABLE 1
Observed gravity at stations on Tungnárjökull.
Station Elev. (m) obs (nigal) Station Elev. (m) obs (mgal) Station Elev. (m) obs (mgal)
N2 679,4 982.102,7 N29 1044,7 003,2 N56 1249,4 941,4
N3 696,7 097,7 N30 1050,1 001,6 N57 1253,9 939,7
N4 715,5 092,9 N31 1057,8 981.999,3 NKP 1257,1 938,3
N5 737,1 087,5 N32 1067,0 996,5 K1 1252,6 940,6
N6 757,0 082,2 N33 1073,6 994,5 K2 1244,1 943,8
N7 776,5 077,1 N34 1082,0 991,9 K3 1239,3 945,8
N8 793,3 072,5 N35 1091,1 989,0 K4 1236,9 946,8
N9 809,7 067,9 N36 1095,8 987,2 K5 1232,3 947,7
N10 826,9 063,4 N37 1102,2 984,9 K6 1223,1 950,1
Nll 840,6 059,9 N38 1109,1 982,7 K7 1218,8 952,1
N12 851,0 056,7 N39 1117,5 980,4 K8 1216,7 954,1
N13 863,7 052,8 N40 1127,5 977,8 K9 1209,0 957,8
N14 874,9 049,7 N41 1136,4 975,1 K10 1205,9 959,6
N15 887,0 046,4 N42 1144,4 972,6 Kll 1206,3 960,4
N16 897,7 043,5 N43 1149,4 971,0 K12 1199,1 963,3
N17 906,4 041,5 N44- 1154,1 969,6 K13 1192,0 965,2
N18 918,5 038,8 N45 1161,7 967,4 K14 1184,4 967,3
N19 934,4 034,7 N46 1171,7 964,8 K15 1175,0 969,2
N20 949,6 030,5 N47 1178,7 963,0 Ivl6 1166,7 970,6
N21 969,5 024,9 N48 1185,7 961,4 K17 1158,8 972,7
N22 982,6 020,9 N49 1194,9 959,4 KI8 1156,7 974,8
N23 985,9 019,5 N50 1208,6 955,6 K19 1155,1 976,9
N24 986,8 018,9 N51 1221,1 951,6 K20 1155,5 978,1
N25 999,6 015,1 N52 1228,5 948,8 K21 1161,9 979,8
N26 1015,8 011,0 N53 1231,5 947,3 K22 1170,4 981,4
N27 1030,8 007,2 N54 1235,6 945,8 SNR 1190,7 977,1
N28 1039,3 004,8 N55 1242,5 943,7
40 JÖKULL 20. ÁR