The purpose of this lab was to use the magnetometer to find out the location, and also how far below the surface of the Earth a metal pipe is. The measurement of variations in the Earth’s magnetic field is used to tell the location of something below the Earth’s surface.
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- Lay out a 25 meter(m) tape measure with the approximate position of the pipe directly in the middle (12.5m)
- Start by taking the measurement with the magnetometer 10 times at the starting point, with 30 seconds between each measurement
- Then take a measurement each half meter along the tape measure for 25 m
- Take 10 more measurements at the starting point with 30 seconds between each measurement. This will be a comparison to evaluate the drift
- Record all data with charts and convert them into graphs for analysis
In this experiment the materials that were used were a magnetometer, 25m measuring tape, stop watch, as well as pen and paper to record data. The data received was somewhat accurate, but there are definitely flaws. There are certain measurements that clearly are not part of the regular pattern. Once the data was plotted on a graph the shape was correct and it was easy to tell where the pipe was located.
Once the data is converted into a line graph, the half width can be found. The half width is significant in this experiment because it shows how deep the pipe is buried. The half width of my graph was approximately 1.8m which means the pipe was about 1.8m deep in the ground. This calculation is exactly why these magnetic measurements are useful.
The drift is the difference in measurements at the same location based on several factors such as solar winds and diurnal variations of the Earth’s field. This is a factor that can affect the accuracy of your data.
One area of possible error was the drift. The two trials of measurement that were taken at the starting position will show how the drift can affect the accuracy. Between the two trials to measure the drift, the measurement changed between a range of 3nT. These measurements were taken at the same spot so they should be the same, which shows how each measurement could possibly be inaccurate. Another area of possible error could have been taking the measurement. The magnetometer must be held very still which could have easily tampered with the accuracy.
Reynolds, J.M. (1997) An Introduction to Applied and Environmental Geophysics, John Wiley and Sons, London. 796 pp.