1. Gathering Location Data with a GPS receiver
GPS units are combination radio receivers and automagic calculators.
The units are tuned to receive time signals sent by a set of 24 satellites on orbit around Earth. By comparing the time it takes for signals from 4 or more of the satellites to reach the receiver, the unit calculates its position.

2. Visualization of 24 GPS satellites orbiting Earth
Visualization of 24 GPS satellites orbiting Earth. Dynamic notation shows total number of satellites with clear line of sight to a point at 45° N on Earth.
Public domain visualization generated by El Pak - available from Wikipedia Commons

5. 1. Walk up to a tree and hold the GPS unit at the trunk.
3. You’ve recorded the location
2. Press and hold OK
4. Press OK again to dismiss the MARK screen then record the other tree data

6. From GPS unit

7. Observations and measurements

8. To retrieve your location data
1. Highlight “Waypoints”
4. Press OK to display waypoint
3. Use arrows to Choose “Nearest”
2. Press
5. Record your data
6. To view you next waypoint, press the Page button then arrow down

9. Optional Integration: Measuring trees in ImageJ
Put a meter stick or a person of known height in your photo.
Open the photo into ImageJ.

10. Click and drag a straight line selection along your known length.

11. Choose Analyze > Set Scale
Enter the known distance and units

12. 1. Drag a straight line selection to the height of the tree.
2. Choose
3. Read Length in Results window