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.

 

[Huyen401]

Hi there,

It sounds like you're on the right track with drawing a triangle and using the correction formula. To find the correction for a specific distance traveled, you can use the following steps:

1. Determine the angle theta for the latitude you are currently at. In this case, it is 45 degrees.

2. Use the distance traveled (25.98 meters) and the azimuth angle (30 degrees) to calculate the distance traveled in the north direction. This can be done using trigonometry, specifically the sine function. The formula is: distance north = distance traveled x sin (azimuth angle).

3. Once you have the distance traveled north, you can plug it into the correction formula: g = -8.108sin(2theta), where theta is the given degree of latitude (45 degrees).

4. Calculate the correction using the distance traveled north and the correction formula. This will give you the correction for that specific distance and latitude.

5. Repeat this process for each reading given to determine the correction for each one.

I hope this helps and good luck with your gravity surveys! Don't hesitate to ask for clarification if you need it.