Recent content by JP O'Donnell

thanks.

Hi. Is it possible for two separate points on an equipotential surface to have two different values for the force field? eg, point A and point B lie on an equipotential surface, but the equipotential surface spacing is much denser at A than at B - so the force field at A as the gradient...

thanks. Appreciate your help.

Hi. Gauss' law applied to gravity states that the gravitational flux through a given surface is proportional to the total enclosed mass. Considering a gaussian surface which encloses a continuous mass distribution, an arbitrary re-distribution of the total mass must yield the same value...

The Free Air anomaly raises theoretical gravity from the reference ellipsoid to the station location for comparison with your gravity reading. However your gravity reading still contains the effects of topographic masses (which you are generally not interested in - you want to isolate density...

Thanks for your replies. Billiards - removal of the gravity effect of the reference ellipsoid is indeed referred to as a latitude correction. Removal of this latitude dependent term results in a gravity anomaly which, upon further reduction, may be used for geological interpretation. The...

Hi. When reducing the value of measured gravity to produce gravity anomalies, the measured gravity is reduced to it's value on the geoid (conventional interpretation). This is then compared to the value generated by the reference ellipsoid at the ellipsoid surface. I would have thought...

Found the reason why... The (1-t2)m/2 term of the function has no effect on the zero's of the function as it will always be positive (|t| = |cos(theta)| =< 1) Therefore the number of crossings will be n-m as stated.

Hi. It is stated that the associated Legendre functions change their sign n-m times in the interval -1 <= t <= 1, where t = cos(theta)... Pnm(t) = {1/(2nn!)}(1 - t2)m/2Dn+m(t2 - 1)n ... Associated Legendre function I can see how this number arises having differentiated (t2 - 1)n...