Given the arguments about gravimeter accuracy in
another thread, I am posting the
theoretical correspondence between latitude and local gravity at height zero at the given latitude.
The point is to highlight how large is the theoretical difference between local gravity at the equator and at the pole, in terms of the units used in gravimetry.
The figures are in microGal, i.e. one millionth of 1 cm per secsq. Note
centimetres not metres, hence the usually quoted number of 9.81 is 981 Gal.
Then note the difference in microG between equator and pole, which is of the order of 5 million, so it is false to say that there is a ‘slight difference’ between gravity at equator and pole.
Modern machines have an error of about 5-10 microG. If you compare actual observations against the theoretical values below, you will find a close correspondence.
I have the formula if anyone is interested.
Latitude , Local gravity microG , Difference
90 , 983 218 620.6 , 5 185 920.6
85 , 983 179 056.6 , 5 146 356.6
80 , 983 061 582.4 , 5 028 882.4
75 , 982 869 811.6 , 4 837 111.6
70 , 982 609 639.3 , 4 576 939.3
65 , 982 289 054.2 , 4 256 354.2
60 , 981 917 886.0 , 3 885 186.0
55 , 981 507 495.9 , 3 474 795.9
50 , 981 070 421.6 , 3 037 721.6
45 , 980 619 987.7 , 2 587 287.7
40 , 980 169 895.9 , 2 137 195.9
35 , 979 733 806.6 , 1 701 106.6
30 , 979 324 925.7 , 1 292 225.7
25 , 978 955 608.7 , 922 908.7
20 , 978 636 993.7 , 604 293.7
15 , 978 378 672.7 , 345 972.7
10 , 978 188 411.1 , 155 711.1
5 , 978 071 921.8 , 39 221.8
0 , 978 032 700.0 , 0.0