| Summary: | The forest industry in British Columbia is converting much
of its spatial data to digital format for input into
Geographic Information Systems. The updating of these large
databases stil l involves digitizing of analog data. This
thesis examines the suitability of a single channel hand
held Global Positioning System (GPS) receiver in the forests
of British Columbia. GPS provides a means of directly
capturing digital spatial attributes in the field. Field
trials to evaluate the effects of forest canopy on the
reception of satellite signals were conducted at the Malcolm
Knapp Research Forest in Maple Ridge.
Issues that need to be considered when implementing GPS in
capturing spatial information are: 1) the frame of reference
from which positions are calculated, (datums) 2) methods
used to calculate the accuracy of position, 3) the accuracy
of single point positions, 4) the accuracy of differential
positioning, and 5) the effects of the forest canopy on the
reception of signals from the satellites. The effect of
choosing a different datum than that used to produce the
base map can lead to positioning errors of several hundred
metres. While commonly the largest source of error, it is
preventable. Single point positions can be expected to be
within 25-metres, in two dimensions, when Selective
Availability is not enabled. When Selective Availability is
enabled the accuracy will be degraded to 100 metres. To
regain the accuracy lost due to Selective Availability,
differential GPS will need to be used. Differentially
corrected positions can be expected to be within 10-metres
in two dimensions. The effect of the canopy on attenuating
the signals emitted from the satellites is of concern. At
best, the user can only expect intermittent signals under a
closed canopy with the equipment tested.
Evolving technologies are increasing the accuracy, speed and
sensitivity of receivers, while decreasing the size, power
consumption, and cost. The integration of GPS with other
positioning and navigational aids shows the most promise for
implementing GPS into forest management in British Columbia. === Forestry, Faculty of === Graduate
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