In a message dated 26/06/2005, tschmitt@.............. writes:

I think  that if you go to a basic geophysics book the sections on
gravimetery will  have some formulas for the attraction of the moon and
sun as a function of  latitude, year,  time of day etc. One has to
correct for those  when doing a gravity survey. The second order
effects are harder to  get and very, very small.
    There is quite a bit of information on gravimeters  at 
_http://www.ecgs.lu/_ (http://www.ecgs.lu/)  The Earth tides  give angular changes of about 50 
to 100 nano radians. 

Absolute  gravity measurements used to be made with pendulums.  I do not
know  how they do them now.  I think they had to stay on station a  long
time,  like longer than the variation due to sun moon  interactions,
however a good geophysics or geodesy book will have that in  it also.  
    The geo survey type used twin pendulums of fused  quartz and optical 
readout. I have given a few more references at 
_http://www.seismicnet.com/psnlist/030520_101305_1.html_ (http://www.seismicnet.com/psnlist/030520_101305_1.html) 
 
    Earth tides are more easily measured using large  water tiltmeters. 
Nicolas d'Oreye's Thesis using measurements at Walferdange is  on line at 
_http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-10172003-155611/_ 
(http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-10172003-155
611/)  It  is listed as a series of chapters. If your French is a bit rusty, 
you might want  to access the sections using babelfish 
_http://babelfish.altavista.com/_ (http://babelfish.altavista.com/) 



Regards,
 
    Chris Chapman





In a message dated 26/06/2005, tschmitt@.............. writes:
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  that if you go to a basic geophysics book the sections on
gravimetery w=
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  have some formulas for the attraction of the moon and
sun as a function=
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  latitude, year,  time of day etc. One has to
correct for thos=
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  when doing a gravity survey. The second order
effects are harder t=
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  get and very, very small.
    There is quite a bit of information on gravimet=
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at http://www.ecgs.lu/ The Earth ti=
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give angular changes of about 50 to 100 nano radians. 
<=
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  style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>Absolute=20
  gravity measurements used to be made with pendulums.  I do not
kno=
w=20
  how they do them now.  I think they had to stay on station a=20
  long
time,  like longer than the variation due to sun moon=20
  interactions,
however a good geophysics or geodesy book will have that=20=
in=20
  it also.  
    The geo survey type used twin pendulums of fuse=
d=20
quartz and optical readout. I have given a few more references at http://www.s=
eismicnet.com/psnlist/030520_101305_1.html
 
    Earth tides are more easily measured using larg=
e=20
water tiltmeters. Nicolas d'Oreye's Thesis using measurements at Walferdange=
 is=20
on line at http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/Be=
lnUcetd-10172003-155611/ It=20
is listed as a series of chapters. If your French is a bit rusty, you might=20=
want=20
to access the sections using babelfish http://babelfish.altavista.com/=



 
    Regards,
 
    Chris Chapman