Check your answers to the GPS device quiz

FIND THE ANSWERS AND EXPLANATIONS TO THE GPS DEVICE QUIZ BELOW. Questions have been listed separately so that you can easily print and use at meetings. Answers follow immediately below questions. Several additional questions have been added as “extras” to the quiz appearing in print. 

1. You are setting up your GPS unit to be compatible with your topographic map. You must:
a) Specify true or magnetic north in the setup menu.
b) Indicate the specified map datum in the setup menu.
c) Select the matching contour interval on the map page.

2. You are planning a canoeing trip and are pleased to note that the UTM coordinates of major obstacles like rapids and falls are indicated on your trip guide. What is “UTM”?
a) An angular coordinate system that replaces latitude/longitude
b) Stands for “Universal Transverse Mercator,” which is a rectangular coordinate system printed on topographic maps. It allows you to pinpoint a map position to the nearest 100 meters or less without using special measuring tools.
c) Same as the military grid reference system. The coordinate system uses two letters and a string of numbers to define a position.

3. When setting up your GPS unit, you must go to the setup menu and:
a) Set the GPS device to read the same units (feet or meters) as your map.
b) Program in the zone number of the map.
c) Program in the contour interval of the coordinates.

4. The elevation reading on your GPS device is 1,633 feet. But contour lines on your topo map read 1,550 feet. Which is more accurate?
a) The map
b) The GPS device
c) Neither one — split the difference and you’ll be right on target

5. Your GPS unit can determine your position even though there are heavy clouds overhead. But the position doesn’t match up with where you know you’re located. What could be wrong?
a) The GPS unit is always more accurate on a sunny day.
b) The GPS unit is getting a two dimensional (2-D) fix, not a 3-D one.
c) The GPS unit isn’t locking onto enough satellites for an accurate fix.

6. One of your Scouts is injured while hiking. You call 911 on your satellite phone and request a medical evacuation. You should give the operator:
a) The UTM coordinates of your position
b) The latitude/longitude of your position
c) The distance you are from the trailhead

7. You change the batteries in your GPS navigator and observe that its electronic compass is no longer accurate. What’s wrong?
a) The compass automatically turned off when the batteries were changed. Go to the setup menu and turn it back on.
b) The compass went out of calibration when you changed batteries. You must recalibrate the compass.
c) Electrical wires are attracting the needle. Move to a different place and try again.

8. You must arrange a medical evacuation, but your camp cannot be seen from the air. You have a GPS device and satellite phone. To make your coordinates as accurate as possible, you should:
a) Keep the GPS device on for a full five minutes. The last reading will be the most accurate one.
b) Turn on “position averaging.” Let the unit run for a few minutes before you take the reading.
c) Allow the unit to obtain a fix, and then turn it off. Wait one minute and turn it on and take another fix. Do this three times. The last reading will be the most accurate.

9. You want to email the UTM coordinates of a waypoint to a friend. Which one of these should you send?
a) Nad 27 / 0628250E / 5291800N
b) U 0628250E / 5291800N
c) Nad 27 / 13U 0628250E / 5291800N
d) 13 0628250E / 5291800N

10. The batteries in your GPS unit are low. What can you do to conserve power?
a) Read the GPS unit bearing to your objective then turn off the GPS device. Set the bearing on your needle compass and follow it. Turn on the GPS device briefly if and when you need an updated bearing.
b) Turn on “simulation” or “demo” mode. Your GPS unit already has enough satellite information to provide updated fixes as you move toward your objective.
c) Nothing. That’s why you should always bring a compass and map!

11. Your topographic map was last updated in 1963. Which of these would make a poor GPS waypoint?
a) The junction of two trails
b) Where a creek runs into a river
c) A high hill
d) A prominent rock outcrop

12. You want to program in the location of a portage in the Boundary Waters. The base map in your GPS shows little detail; your paper map is detailed but it doesn’t have coordinates (UTM or latitude/longitude) printed on its face. How can you accurately plot the location of the portage?
a) Enlarge the scale of the GPS base map until the GPS and map scales are equal. Then plot the waypoint (portage).
b) Use your orienteering compass to plot a bearing to the portage. Set this bearing on your GPS and follow it.
c) You can’t accurately plot the location of the portage.
d) Program the elevation of the portage into your GPS, and then follow the bearing to it.

13. Programming GPS waypoints can be tricky. One wrong digit and you could be thousands of meters off! How can you check the accuracy of your plotted coordinates?
a) Just look at the map and see if they agree
b) In the setup menu, change the position coordinates to latitude/longitude. Then roughly plot them on your map. If they cross near your waypoint, your UTM numbers are correct.
c) Reference the UTM coordinates to grid north, not true north.
d) First, correct the point for magnetic declination, then count up the grid squares and plot the point on the map.

14. When reading map coordinates, you should always read:
a) the easting coordinate first, then the northing coordinate.
b) the northing coordinate first, then the easting coordinate.
c) the north coordinate first, then the east coordinate.
d) the south coordinate first, then the west coordinate.

15. Accuracy of the typical civilian GPS is about:
a) 5 meters
b) 15 meters
c) 150 meters
d) 1,500 meters

16. Some GPS receivers are equipped with WAAS (Wide Area Augmentation System). Which of these are true?
a) WAAS provides GPS corrections, which produce greater accuracy than units without WAAS.
b) A WAAS capable receiver can provide position accuracy of better than 3 meters, 95 percent of the time.
c) WAAS isn’t free. You have to subscribe to a payment plan.
d) There is no charge for using WAAS, but you must fill out a form and send it to the FAA.

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ANSWERS

1. (b) A datum is part of a shape that best fits the part of the world that’s indicated on your map. There are many different datums. If your GPS uses a different datum than your map, your position fix will be in error. You’ll find the datum in the lower margin of every topographic map. The most popular datum is WGS 84 (World Geodetic System, 1984), which also is the default datum of your GPS. Your GPS will provide a correct map position whether you choose true or magnetic north.

2. (b)

3. (a) or (b)

4. (a) GPS elevations are often less accurate than map elevations and inaccurate when the GPS is in 2D mode.

5. (b)

6. (b) Aircraft work in latitude/longitude, not UTM. If you provide UTM coordinates, they must include the zone and row number so that they can be converted to lat/lon. Without it, the dispatcher won’t know where you are!

7. (b) If you want accurate readings, you must recalibrate the compass every time you change batteries.

8. (b) will result in improved accuracy. However, not all GPS units allow position averaging or have a position error indicator.

9. (c) You must include both the zone number (13 here) and row number (U). Without these, your friend won’t have a clue where you are. It’s also wise to provide the map datum (Nad 27 here) in the event your friend‘s map uses a different datum.

10. (a) could save the day!

11. (a) It’s always best to choose a geological feature over a man-made one, which can change over time. The trail may no longer exist.

12. (c) Your map must have a coordinate system to which your GPS can relate. Not all maps do.

13. (b) is a foolproof way to check your UTM numbers. If you are thousands of meters off (easy with UTM!), your latitude/longitude plot will be off the map. (a) is unreliable because you will probably repeat your mistake.

14. (a). The rule is to “read right then up” — that is, the easting coordinate first, northing second. Surprisingly, some GPS units reverse the coordinates — a confusing practice.

15. (b) About 10-15 meters without WAAS turned on.

16. (a) or (b)