GPS in Schools – Worksheet 2
Produced by the University of Tasmania in conjunction with Geoscience Australia as part of the AuScope GPS in Schools Project – 2014.
4
7.
Split into groups of three or more people and find the
waypoint function on your GPS receiver. Get one member of
your group to go off and secretly mark a waypoint at a
significant feature (e.g. the door to the science building, the
swings in the playground or the goal post on the oval), but be
sure not to tell the rest of your team what’s been marked!
Once complete, get the remaining team members to use the
GPS receiver to navigate to the secret waypoint. Repeat this
process for each member of the team, so everybody has a
chance to mark a waypoint.
Was your team able to accurately identify each of the secret
features? Were the GPS directions reliable? Why/why not?
If each waypoint was marked in a clear area, the accuracy of the final position should be good. If,
however, the waypoints chosen are alongside a building or in an area of poor skyview, the waypoint
accuracy may decrease. Directions to each waypoint should be reliable in areas of good sky view, but
may degrade in areas of poor skyview or if the GPS is stationary when trying to navigate (must be kept
moving for directions to be reliable).
8.
Choose an identifiable feature with a clear sky view (e.g. edges of an oval, the shoreline along a beach or
the edge of some bushland) that you would like to map. Trace out the boundaries of your chosen feature by
recording a track on your GPS receiver and walking along the boundary. Be sure to save your track with a
relevant name on completion, as it will be needed in Part 2.
Worksheet 2 – Part 2 (Data Transfer and Mapping)
9.
Download the two GPS tracks from Question 4 and Question 8 and the waypoints from Question 7 onto your
computer. A cable will be required for most traditional GPS receivers, while most GPS apps provide a
‘share’ or ‘export via email’ function (see the information sheet for further details). Ensure your file is in ‘kmz’
or ‘kml’ format (if not, you will have to convert it – see the information sheet for further details).
10.
Open Google Earth and load the track from Question 4. Measure the distance of the track using the ‘Ruler’
tool. How does it compare to the distance you measured with a tape in Question 3? Is it longer or shorter
than the taped distance? Why?
The GPS distance and the tape distance are unlikely to match identically. This is because the start of the
GPS track is only accurate to ~5 m, and the end of the track is only accurate to ~5 m. This means there
may be an error of up to 10 m between the taped and GPS distances. Other sources of error include any
accuracy limitations of the Google Earth imagery and ‘Ruler’ tool. The taped distance is the more
reliable measure.
11.
The table below lists several scenarios that require distance to be measured. For each scenario, tick whether
you would use A) a 30m tape or B) a GPS to complete each task. Keep in mind the accuracy and practicality
of each technique as it applies to each scenario.
Scenario
30m Tape
GPS
Setting out a 5m x 5m square on the oval
Measuring the length of a runway
