Global Positioning System Reference
In-Depth Information
The importance of 4D maps in creating value is clearly very high but it does
create serious technical challenges, particularly the issues of scalability, latency,
and availability.
The scale issue concerns the burden of processing (and investments to
provide it) required to perform regular 4D calculations to check the status of each
event instance being monitored. In the extreme there could be several event types
being monitored for each driving vehicle, active person, or important object.
Latency (or the delay in processing or communications) if too great can lead to
time critical deadlines being missed or confusion about whether an event has
happened or not. Availability of networks, positioning signals, or mapped areas
leads to patchy services and unreliability. These challenges are to an extent linked
but all contribute to the overall quality of service (QoS).
8.8.4
Carrier Scale Whereness
A strong incentive to use a converged Whereness system is that QoS can be
managed more effectively and efficiently. Sometimes the term “carrier scale” is
used to describe the robust nature of the trunk telecommunications networks that
underpin international telephony and the Internet. Whereness operated on a
similar scale by similar organizations should lead to a similar QoS.
8.8.5
Time Calculations
If we wish to include time in the maps, it is likely that time will be represented by
a period and not by an instant, so we need four values for the upper and lower
bounds of the start and end of the period in question. This is needed to help deal
with queries such as, “When the planned roadworks are in progress, will the truck
in question be delayed?”
The road would be defined as the ribbonlike area defined by the nodes
representing its geometry and the truck as a position probability (probably an
ellipse, since positioning errors are often better in one direction), but both road
and truck would be qualified by time bounds. For the truck the timing may be
based on its GPS tracklog.
