Gravity corrections- latitude correction

[subopolois]

i have i problem with many parts to it that the forums may be able to help me with. I've been given a scenario which involves gravity surveys along a path, in summary here it is:

a gravity survey is taken at an initial latitude of 45 degrees and has an azimuth of 30 degrees.

ive also been given a list of gravity data readings, but its not the problem. the question asks to apply necessairy corrections and i know latitude correction is one. my problem is how to determine the correction for each reading given. i know i have to draw a triangle from the start (45 degrees) and a line going out from there 30 degrees. i have found the distance I've traveled north when i travel along the azimuth.

we have been given a correction formula: g= -8.108 sin 2 theta where theta is the given degree of latitude.

at this point i am stuck. how do you find the correction for example if i move 25.98 meters in a north direction?

 

[Redbelly98]

There is an equation for g vs. latitude at

http://en.wikipedia.org/wiki/Earth's_gravity

Scroll about 1/2-way down the page. Just after the section title "Mathematical models", you'll see the equation.

p.s. Welcome to PF.