105Lab01GPS - Name _ Group _ Geol 105 Lab Exercise #1 Week...

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Name ________________________ Group ____________ Geol 105 Lab Exercise #1 Week of Jan. 16-20, 2012 Using Compasses, Maps and the Global Positioning System in Earth Science PART A. INTRODUCTION Spatial information, that is the location of data or objects, is invaluable information both in scientific studies as well as for everyday living. For example many boats and all airplanes have devices to constantly track their location. Runners use such devices to keep track of their speed. In the sciences we often make measurements on objects in our universe and in many cases want to know the spatial relationship (direction and distance) between these measurements. In this lab we will begin to learn how to use GPS (global positioning system) to locate objects (including ourselves) and how we can use these locations to navigate and thus to evaluate motion of objects (that is position through time). GPS Unit: Below is a diagram illustrating the functions of the buttons on a handheld GPS Unit. Turn the GPS Unit on by holding down the Power Button . Hold the GPS level for 2-4 minutes in an open area with no tree cover to allow the unit to contact the satellites. The first screen to appear will show you the locations of all the satellites in your hemisphere, and the signal strength of each satellite. Triangulation The length of time required for your transmitter to receive signals from each satellite is translated into a distance between you and that particular satellite. This distance can be plotted as a circle on a map (since the direction is not known but distance is fixed and must end up on the earth’s surface). Fig. 1. eTrex Summit buttons 1 of 11
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Two such circles (from two different satellites) overlap and narrows your potential location down to 2 points: three circles overlap in a very small region and tells your GPS unit “exactly” (with a few meters) where you are. So, you must have a strong signal from at least three satellites to locate. When your GPS is ready, it will tell you within how many feet, or meters, you can currently locate yourself. Compass: We can use a GPS receiver to determine multiple positions and thus distances and directions. But this requires that we move around and record these points. Sometimes we want to determine directions at one point. Compasses are useful tools for doing so.
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This note was uploaded on 04/02/2012 for the course GEOL 105 taught by Professor Platt,davis during the Spring '08 term at USC.

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105Lab01GPS - Name _ Group _ Geol 105 Lab Exercise #1 Week...

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