Precision Measurement

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Fig.1: The Spiegel-Relaskop mounted on a tripod with tilting head and micro
attachment for precisions measurements

  • 1 long handle of the tilting head 7 lever to fix 8
  • 2 knurling knob for vertical adjustment 8 socket plate with screw bolt
  • 3, 5 locking screws for tilting head 9 stop pin
  • 4 knurling knob for horizontal adjustment 10 stop and device for permanent
  • 6 locking break release for the Spiegel-Relaskop release of the brake

The use of the micro attachment is as follows (see Fig. 1): A rough adjustment of the height is made by the long handle (1) of the tilting head and can be read from the scale of the Spiegel-Relaskop after depressing the locking brake release (6). The device for permanent release of the brake (10) is moved therefore into position to keep the brake  release  depressed. The internal  pendulum  now swings  freely and will continuously adjust for changes in inclination, which can be made using the adjusting knob (2). The locking screw (3) of the tilting head gives a rough horizontal adjustment, whereas the adjusting knob (4) allows a very precise adjustment needed for measuring widths. The locking screw (5) provides for sideways tilting of the tilting head, where there is no need for precise adjustment.

3-point Measurement with the Micro Attachment

The Spiegel-Relaskop should be used as close to the stem as possible. The following procedure is recommended (see Fig. 2):

After selecting a suitable observation point (preferably on the uphill side of the tree) take the readings for the inclination p to the diameter at breast height and for the width b at that point. Then take the readings for the inclination p2 and width b2 of a second point higher on the tree.

Each of the readings for p and b are taken with the instrument in the same position. In this example p = -34 is read on the percentage scale. For measuring width, the left edge of the tree must be aligned with the left edge of one of the RU bands so that the right edge of the tree falls within the quarters field. Now count the full RUs to the left of 0 (see Fig. 1 for details of CP-scale) (1 RU = 2%), the quarter fields to the right of 0, and estimate to the nearest 1/10 RU. In this example, the relative value of b is therefore equal to 11.6 %. Multiplying by the distance a in meters will give the absolute value of the diameter in centimetres:

d (in cm) = a (in m) ∙ b (in %)

At the second point  higher up  the tree, follow  the same  procedure (b2 = 8,5 %). From this same point near the tree, if possible, measure

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Fig. 2:  Example of a three-point measurement on a single tree

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