Global Positioning System Reference
In-Depth Information
people navigate, which is often by way of landmarks that may be detected by
various sensors.
For example in their paper Schindler et al. [11] describe a very simple
positioning SLAM-like system that uses a wearable device consisting of a
modified set of spectacles. It detects doorways between rooms by shining infrared
beams sideways and looking for the characteristic reflection with distance being
measured by a simple accelerometer chip-based pedometer.
Mapped information must be self-consistent and topologically correct. If
loops are mapped they should be made to close up. If a multiple set of tracks all
slightly offset are detected, they can be condensed into a single track. The great
strength of the technique is that it is a closed loop control system. If the post-
processing stage performs a consistency edit, it will be confirmed or rejected
when the map is next reused.
The main difference between a robot exploring and mapping a space and a
human “robotics” mapmaker is that the former may move into uncharted areas just
to explore whereas it is more likely that people will be following definite routes
with a purpose in mind. Human mapping will tend to map where people are likely
to go, whereas a robotic explorer may be sent on more random mapping mission
in open spaces.
Spaces are sometimes processed as occupancy grids. The likelihood of being
in a certain place (based on measurements) is calculated statistically for each grid
square in a given area. Another technique is to convert free space into a non-
regular graphical grid and use a Voronoi diagram. Obstacles are assigned as grid
points anywhere they are detected and equidistant loci between the points are
plotted as places where it is possible to be located.
9.5
A Long term Vision
In this topic we have covered a large number of concepts, many of which are
speculative and suggest a future computing and communications environment that
is unfamiliar today. So what might the developed world be like, for example, in
ten years' time?
In a decade of so we can expect basic computing devices to be faster, smaller,
cheaper, and more common, in line with the general trend that is supported by
Moore's law arguments. The processing and storage tasks that would be
associated with quite expensive personal appliances such as vehicle navigation
units and personal smart phones would be included in much more basic units,
leading to the possibility that virtually every working person and school student
would carry a personal positioning device that would receive a basic set of signals
from several GNSS systems and have connectivity by both cellular radio and
hotspots. These devices would be used to organize intelligent transport at a
regional and national level where the environmental impact of most journeys is
calculated and tolled.
