Haga
From AWF-Wiki
Contents |
General description
Haga is a device to measure tree heights within fixed distances of 15, 20, 25 and 30m to the tree by the trigonometric principle and slope in percent. The suitable scale can be selected by rotating the adjustment disk at the front of the device. A reference tape can be installed at the tree to determine the distance optically.
Figure 1: Haga altimeter
Using a Haga altimeter
Handling
The handling of the Haga is very similar to the Blume-Leiss instrument.
Distance measurement
- Place the reference tape at the tree,
- Determine an optimal distance to the tree by checking the view field to tree bottom and top within the forest stand - preferably 15, 20, 25 or 30m,
Height measurement
- Select the corresponding height scale by turning the adjustment disk,
- Sight tree bottom, lock the pointer needle and remember the value,
- Sight tree crown, lock the pointer needle and remember the value,
- The difference between the measurements will be tree height: $h_t=h_c-h_b$.
Figure 2: Live view measuring tree bottom
Figure 3: Live view measuring tree crown
Note:
- When measuring with Haga, take care that the pendulum has stopped oscillating before locking the button. Be careful of choosing the scale corrosponding to your actual distance!
| Advantages | Disadvantages |
|---|---|
| slope correction implemented | correction factors list hast to be carried in the field extra |
| optical distance measurement | dependance on fixed scales (could be difficult in closed forest stands) |
| independence of power sources (no batteries needed) | in dark forest stand optical measurement is difficult |
| only one needle for measurements implemented | |
| no digital storage of measurement results available |
Applications
