Introduction Basics of GPS Prepretory Exercises Explore your GPS Record Data Find Yourself Field Exercise Results GeoSTAC

Find Yourself on a Map

. . . by Jacob Mundt

This portion of the exercise will allow you to use a GPS coordinate to locate a position on a map.

First, you will need to get together your materials including your map, ruler, and have your GPS unit handy. Make sure that your topographic map covers the area that you previously acquired GPS data from.

Lay your map out on a flat table. Look at the coordinate axes and locate the axes that correspond to the coordinates you collected data using. Notice that the map is sectioned into a coordinate grid. Using your ruler, you can divide and rescale the coordinate units on the map to get a precise location.

Now, using the GPS waypoint locations coordinates you previously collected, you can scale using your ruler and the map coordinates.

• Do they lay in about the right place?

• Are they EXACTLY correct?

• What might be the reason that they might not be exactly right?

• Do you know the error on your base (topographic) map and your GPS?

• How might these errors compound or cancel each other out?

A very useful resource is a ruler that is scaled to your map units. Download a PDF of UTM Grid Rulers for 1:24000 and 1:12000 scale maps. If you do not know what the scale of your map is, you should visit the Topographic Maps Module.

This exercise should be repeated several times with points that are easy to locate.

DO NOT ATTEMPT TO GO FOREWARD if you do not have a complete understanding of the previous steps or if you can not answer the above questions.