Geography Reference
In-Depth Information
displacements of each antenna with respect to the reference antenna, using diagrams and
tables. The GUI can be tailored to the customer's requirements, and it will alert the operator
when preset thresholds are exceeded.
The main disadvantage of the SEPA types fixed systems is that this equipment must be
mounted in a fixed position on every point of interest, meaning that for an objective or an
area suspected to present landslides, a great number of equipments of this kind is necessary,
and, in consequence, high total costs.
Taking account of the newest improvements of the GNSS systems regarding the real-time
positioning accuracy, (A. Stoica et al., 2008), the authors of this chapter present the
achievement of a mobile equipment for the monitoring of the field stability as opposed to
the most used in present, static optical total stations, “Leica” or “SEPA” type systems, which
are based on GPS receivers with differential regime functioning but which are fixed
mounted on the surveyed objectives.
3.2. Existing mobile mapping equipments
But one must specify that also for this mobile alternative, which is proposed here for the
monitoring of some objective position, there are various mobile equipments for mapping
and, respectively, for monitoring, introduced on international level, equipments which are
described in the following subsections.
3.2.1. “GPSVision
TM
” achieved by the “LAMBDA TECH International” company
(Guangping He, 1996)
The Mobile Mapping Equipment “GPSVision
TM
” (fig. 5) achieved by the “LAMBDA TECH
International” company from Fort Wayne (USA), which is equipped with a positioning
module composed of a GPS receiver with double frequency, an Inertial Navigation System
(INS) and a linear Distance of running Measuring Instrument (DMI), in combination with four
digital video cameras of high resolution. The digital video cameras are mounted above the
vehicle and they can be oriented forward, to each side or backward in correspondence with the
application needs, so that due to the fact that the video cameras pairs see, at a certain moment,
the same field area from different positions, by using some triangulation algorithms, it is
possible to calculate the locations relative to the lab vehicle of the sighted targets.
The main characteristics of the system are:
The images are taken according to an operator-defined distance interval to provide full
coverage of the route and its surroundings. By applying a sophisticated
photogrammetric triangulation technology, any point that appears in any set of two
images can be located in a global coordinate system during digitization with Lambda
Tech's Feature Extraction software;
Stereo imaging allows for determining absolute positions of features such as signs in
latitude and longitude to sub-meter accuracy and it also allows very accurate relative
measurements of all visible roadside attributes, such as the width, height and offset of a
