The Bitterlich relascope (Austrian designer Walter Bitterlich) is a multifunctional device that can be used to make an angle count sample to estimate basal area depending on basal area factor. Additionally it can be used for height measurements by the trigonometric principle and to measure upper diameters in different heights to estimate form heights, form numbers and scape volumes for trees.
The relascope is constructed with a cylinder pendulum which enables automatic slope correction for each estimate. Therefore you will have to press the button at the front of the device till the pendel stops moving (to be sure, that the slope is included) – disengage the button to lock the scales. The visual appearance while looking through the relascope is constructed as a horizontal sighting which appears in the half of the view.
If the light is too bright, you can darken the scales by moving up a small bar, which is assembled at the front of the device.
The following table gives a short description of the different scales implemented in the relascope.
|Ts 20 (Tangent scale)||height measurement for distance 20m|
|BAF 1 (basal area factor 1)||angel count method for basal area factor =1|
|BAF 4 (basal area factor 4)||angel count method for basal area factor =4 (BAF 1 combined with the following 4 relascope units)|
|Ts 25 (Tangent scale)||height measurement for distance 25m|
|Ts 30 (Tangent scale)||height measurement for distance 30m|
|BAF 2 (basal area factor 2)||angel count method for basal area factor =2|
|Ds 30||distance scale for a 2m vertical base to measure horizontal distance of 30m|
|Ds 25||distance scale for a 2m vertical base to measure horizontal distance of 25m|
|Ds 20||distance scale for a 2m vertical base to measure horizontal distance of 20m|
|Ds 15||distance scale for a 2m vertical base to measure horizontal distance of 15m|
To do an angle count look through the device and press the lock button so that pendulum can work to do automatically a slope correction. Choose a basal area factor and count all trees that appear bigger than the respective scale in a 360° turn. An estimate of basal area (m²/ha) can be calculated by multiplying the counted number with the basal area factor (for theory see Bitterlich sampling).
For a detailed description of the different scales and handling please see the manual. Below a few case examples are given doing an angle count sample.
|multifunctional device – parameters to describe the form single trees and also forest stand parameters can be derived||in dark forest stand optical measurement is difficult, no digital storage of measurement results available.|
|slope correction implemented|
|independence of power sources (no batteries needed)|
To measure large tree diameters in different heights, Bitterlich has developed a relascope with another broad scale view.
Here a scale is implemented to measure slope in degrees and percentage, and scales for basal area factors up to 11.