SO503 Honors Modern Methods

Spring 2017

Lab 1: The Spreadsheet, Filtering, GPS

Lab Objectives:

1.  Learn how to import an ASCII text file into the spreadsheet and use it for numerical calculations. Understand the two ways ASCII files can be arranged (fixed width and delimited).

2.  Know how to use if and trig functions (radians and quadrants for inverse functions) in the spreadsheet.

3. Get time into a useful format for numerical computations.

4. Understand one dimensional numerical filtering.

5. Consider how directional data is different from other numerical data.

6. Learn something about GPS data and the Mercator projection.

The data files you need are called norm_gps_1.txt and norm_gps_2.txt.

These two files are taken with a small data logger which we are evaluating for use in a research project tracking wildlife.  We want to answer the following questions:

• What units does the logger use for recording speed?

• Does the unit record speed with sufficient accuracy, or will we have to compute it from the raw data?

• If we have to compute speed from the raw data, how noisy is the data and will we have to filter it?

This lab will be individual effort; you will document on the write-up any assistance you receive (if none, explicitly state).

Due in the Blackboard assignment dropbox (e.g. YourName_Lab1_gps_speed.doc) as specified on the syllabus:

• Graph(s) with the speed of the unit as a function of time, and with a filter that averages 3, 5, and 7 readings, for both files, and  a median filter with what you consider to be the best number of terms. You can do this as one single graph for both data sets or two separate graphs.  You might also want to blow up part of the time axis so that you can see what the filters do.

• Table for 20 readings with Time (center of interval, think about the best units), Duration of Time interval, Distance covered in interval (meters), Speed during interval (meters per second),  Averaged speed over 3, 5, and 7 time intervals centered on the desired time, and your median filter.  This will be for the first 20 readings of the gps_1 file.

• Graph of the track of the unit (strictly speaking you should make sure that the physical dimensions of the x and y axes are the same, and then you would have a Mercator map projection, but you can ignore this minor point) for both data files.  You can do this as one single graph or two separate graphs.

• Graph of the heading of the unit (compass degrees) as a function of time for the two files.

• The table and graph(s) will be included in your Word document,  labeled in accord with the department style manual, and referenced in your discussion.

• Discuss answers to the following questions, as a coherent discussion and not a simple question/answer cut and paste job.

• How does filtering affect the graph of the speed?  What size filter do you think best reflects the true speed, and why? How do the median and averaging filters differ?

• How would averaging or filtering the azimuth data be different than the same operations on the speed data? (While you are not required to do this, you may want to actually try this to help in answering this question.)

• An acknowledgements section, profusely thanking any classmates or others who helped you.

General guidance:

1.  These directions are not a cookbook for how to do the lab.  Learning to think is probably the most important thing you will get from your education here at USNA, and this course in particular.  If you have problems, see me before you spin you wheels forever.

2.  The discussion is designed to make you think.  Your thought process is as important as the "correct" answer, which we will go over eventually.