POSITIONING OF INDIVIDUAL TREES
Use the Postex system in your preferred system configuration to position trees and other objects in sample plots.
Use the Postex system in your preferred system configuration to position trees and other objects in sample plots.
With both ultrasound and laser technology available in the Postex instrument, height measurements can be made made in different types of forests. The ultrasound method will not limit you to a line of sight. One person can position all types of trees including seedlings accurately and perform the complete job of electronically capturing all tree and other object data into one seamless system. Choose between three Postex system configurations all with efficient positioning as main focus.
PosTex system
Abstract from The Haglöf PosTex ultrasound instrument for the positioning of objects on forest sample plots by Tomas Lämås, SLU Sveriges Lantbruksuniversitet, Institutionen för skoglig resurshushållning, Umeå, www.srh.slu.se. Arbetsrapport [work report] 296 2010, ISSN 1401-124; ISRN SLU-SRG-AR-296-SE
The positions of objects – typically trees and other vegetation – in forest sample plots are often of interest, e.g., as ground truth data in forest surveys in which remote sensing techniques are used, and in environmental monitoring. Laser rangefinders and measurements of bearings using electronic compasses are often used for this purpose. However, use of laser rangefinders is problematic when sighting conditions are poor. In contrast, since ultrasound passes through vegetation and around stems it also enables measurements in dense forest. Thus, the novel ultrasound–based Haglöf PosTex® instrument provides quick measurements of positions of objects in sample plots even in dense forest with poor sighting conditions. The design of the instrument also enables measurements of positions at the same time data are recorded for the objects, such as the diameters of trees. The instrument – developed in collaboration between the Swedish University of Agricultural Sciences (SLU) and Haglöf Sweden AB – has been used in various applications, e.g. in forest remote-sensing projects and mapping mountain vegetation, trees in burnt forests and seedlings for monitoring forest regeneration.
SUMMARY OF ACCURACY IN FIELD TESTS
In the above mentioned study the accuracy of the PosTex instrument was tested in three sample plots, below are a summary of the results reported.
TEST 1
Old spruce and pine dominated forest. 7 trees between 9,1m/29,9ft. and 10,8m/35,4ft. from the plot center. Each tree was measured 8 times which gives an amount of 56 observations. The plot contained significantly more trees.
Mean deviation 20,3 cm/8″.
Standard deviation 13,4 cm/5,28″.
90 % of the observations were within 30,1 cm/11,85″. from the true coordinate.
TEST 2
Old pine forest, 5 trees between 7,9m/25,9ft. and 10 m/32,8ft. from the plot center. Each tree was measured 16 times which gives an amount of 80 observations.
Mean deviation 4,9 cm/1,93″.
Standard deviation 3,2 cm/1,26″.
90 % of the observations were within 9 cm/3,54″. from the true coordinate.
TEST 3
Dense spruce and pine dominated forest before thinning, 6 trees between 6,8m/22,3ft. and 11,3 m/37,1ft from the plot center. Each tree was measured 8 times which gives an amount of 48 observations.
Mean deviation 14,5 cm/5,71″.
Standard deviation 9,6 cm/3,78″.
90 % of the observations were within 29,3 cm/11,54″. from the true coordinate.
Other
The distance measuring is very well consistent. In the field test above the radius deviated with in average 0-3 cm/0-1,18″. with a standard deviation of 2 cm/0,79″. The PosTex error increases with increased distance according to Lämås. More accurate positions are measured closer to the plot center and more uncertain results are obtained in the sample plots periphery.
”True coordinate” is a position measured with a total station (electronic theodolite with a laser rangefinder).
For further information see the complete work report: The Haglöf PosTex ultrasound instrument for the positioning of objects on forest sample plots by Tomas Lämås, SLU Sveriges Lantbruksuniversitet, Institutionen för skoglig resurshushållning, Umeå, www.srh.slu.se. Arbetsrapport [work report] 296 2010, ISSN 1401-124; ISRN SLU-SRG-AR-296-SE
How to use the Postex system
DP POSTEX and Computer caliper DP II
How to use the Postex system
Postex Laser and Computer caliper DP II.
