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Record Data with GPS Unit

. . .by Jacob Mundt

Garmin Grade GPS receivers are commonly used to map point locations for features of interest. These point locations are stored as 'waypoints' in your GPS receiver. Each waypoint has a unique name and location. You can also choose to save your waypoints as part of a route, marking positions along the way to a specific destination.

Starting simple: Outside, in an open area turn within the boundaries of your topographic map, turn on your GPS and navigate around. On the position screen, you should be able to see the numbers move as you walk. Walk North, South, East and West, the numbers should change accordingly.

Now skip to the compass screen. Keep in mind that you must be moving in order to have the GPS give you a correct estimate of the direction you are going. Also, remember that the GPS only tells you which way you are going, NOT which way the GPS is pointed. Move in different directions for a few minutes and get a feel for how the compass works.

On the GPS, navigate to the satellite screen. Now walk closer to (or directly under) a tree, power line, cliff (safely) or building. You should notice that as you get closer to large objects, you should begin to degrade the signal from your satellites. This is a practical example of masking and multi-path errors. The power lines may or may not affect you greatly, however it is not uncommon to get bad readings from under or near power lines due to electrical interference.

MARK A POSITION

The fastest and easiest way to mark a GPS point is to simple push the 'MARK' button. A new screen will come up that displays the default name and symbol of the point, the location in the units that your GPS is set to, and an 'add to route' feature.

The name of your new waypoint is easy to change, and should be changed to keep things straight. You can name this whatever you want that makes sense. To change the name, scroll to the default name and press the 'ENTER' key. Then you will see that you have a blank area to create a name. Alpha numeric characters will appear as you press the up and down arrows. When you are finished, press the 'ENTER' button again.

To change the symbol, scroll to the symbol and push 'ENTER'. Follow the menus and select the symbol of interest.

Verify that you are in the coordinate system you want.

If you would like to add this point to a route (if you are mapping a road or trail or some other linear feature), you can do that at this time by selecting which route you would like the point to go into.

Now you can save this point. If you prefer, you can select to average several points (recommended). Recall from previous exercises that the accuracy from a GPS is somewhat poor for only using a single estimate, so taking many points and averaging them together will produce a more accurate result. As the points average, you will see the error reduce. When you are satisfied with your point estimate, select to save.

VIEW YOUR POSITION

Now walk for a minute or so away from the place you just stood. On the GPS navigate your way to the Main Menu, and select to view waypoint list. On opening the list you can browse to the waypoint you just took, and open it up for review. You will see the position, date and time. You will also see how far and in what direction you are from this waypoint. Evaluate this information for accuracy.

Also, you can choose to select the 'GOTO' button. Navigating from the menu (after you push GOTO), you can select your waypoint again. You should receive the same information as you did in the previous step. This feature is very handy when you mark a point that you will be interested in returning to (such as an interesting rock, fishing hole, or your car).

Now, navigate on the GPS to the map screen. You should see your point on the map, and your current location as well. Play with the map options a bit, you can change the zoom level, orientation, and more.

Make sure for the next step that you map at least one feature that you will be able to locate on your topographic map. Features may include road intersections, trail crossings, river bridges, etc.

Now you have taken and saved some GPS data. In the next exercise, you will compare the GPS coordinates you acquired with map coordinates.