A
SMALL DOSE OF STATISTICS
Dr. Don Stierman - updated 2006
“A man with one watch knows what time
it is. A man with two watches is
never quite certain.”[1]
We have a similar problem with geographical coordinates supplied by a GPS
receiver. As you stood in one
location, latitude, longitude and elevation kept changing.
No, plate tectonics was not responsible for this apparent motion.
One problem associated with measurements is uncertainty,
or error.
By “error” I do not mean mistakes or incorrectness.
“Error” in this context refers to the degree of uncertainty.
During the field GPS lab, students used Trimble GeoExplorer II GPS receivers to collect location information. These locations were stored in GEII memory, downloaded to computers, and differential corrections calculated.[2] You have lists, provided by the teaching assistant, of corrected and uncorrected locations. Instead of latitude and longitude, these locations are listed in terms of “military grid”, or UTM (Universal Transverse Mercator), a Cartesian (X and Y axes at right angles to one another) system many find more convenient for local maps than latitude and longitude. What is the best value you can write for each location where GPS readings were collected?