Author Archive for tamasdecsi

With prices falling and new devices appearing on the market every week, it seems that GPS car navigation systems are finally getting widely adopted. Still, the question remains whether they are ready to be used by the “average driver”?

Sure, it is useful to know where you are, and in what general direction your destination is, what more, how on Earth can you get there on four wheels. All this requires a GPS receiver (to read your current location), a mapping software (to calculate your moving direction from subsequent reads), and an accurate map (to give some context and meaning to your location readouts). The first two are more or less out there. Still, maps can be considered anything but reliable or accurate.

With news on blind faith put in navigation systems, people have already got wet, others found themselves down the stream, on the track, or fighting the dunes, the map inaccuracy issue finally got into the headlines.
People, of course, are eager to come up with various solutions.
* An almost-victim said she won’t ever use a navigation system again.
* others said people should update the maps in their navigation systems every once in a while
* some Welsh officers has even created a new, but ambiguous traffic sign to warn lorry drivers of the road being narrower than expected.
* while others came up with fairly good ideas, such as superimposing the map on a front-camera’s stream, so that even faithful users can compare the map with the reality on the same screen.

However, keeping maps up-to-date is not as simple as one may think. Downloading the latest updates doesn’t do the trick. Maps become inaccurate at (or even before) the very moment they are published. As it is their purpose to sketch the spatial layout of real-world features, the only way they can remain up to date is if they constantly evolve along with their “mapped” real-life features. And constantly means very short term here. Think of traffic, for example: maps that fails to mention actual road congestion, current roadworks or accidents, has only a limited use, routing their users through nasty traffic jams.

In order to better understand the situation, first let’s take a look at the various approaches of creating and updating maps:

The commercial route is what proprietary navigation software vendors take. Usually you get these applications bundled with a GPS receiver, and preloaded with some not-too-up-to-date maps. The map data used by them is something commercially available, which most likely originates from the digitized version of maps of the “pen and pencil” era, with updates from geocoded aerial photography, and most likely not thoroughly validated by actual GPS reading on the ground. User feedbacks are usually welcome, and the major inaccuracies gradually get updated , but that’s a slow process, and the more recent map you need the more deep you need to dig into your wallet for it.

On the other end, there are the open approaches, thinking of open source projects with an enthusiastic community of hobbyists and professionals dedicating their free time to make something useful or at least interesting.

These projects take different approaches to acquire map data.
Some of them make use of openly available data (where there is such a thing), for example, Roadmap uses the TIGER GIS data, where of course, data accuracy is limited again.

Others, such as gpsdrive use dumbed down version of “available” data in form of snapshots of rendered maps from various web map services, such as google maps or yahoo maps to mention the two biggest. This approach can’t do routing, though, as the map is treated as a simple raster image only, without any routing information or so.

Yet another approach is based on a mapping community, and let contributors draw the maps, like cgpsmapper’s MapCenter, or the geocaching communities offsprings (e.g. turistautak for Hungary), or the very active openstreetmap project, or the much less active FREEMAP project to mention a few. The resulting maps are definitely GPS-validated, as the data source itself is the GPS tracks gathered, but it takes enormous amount of total community time to create a quite complete, routable map for even a relatively small region, nonetheless, quite impressive results already exist.

Still another concept is algorithmic map generation from GPS tracks, using statistical methods, thus reducing the amount of expertise needed on the map creation side. Mapgeneration takes this algorithmic map-drawing route. The problem (again) is gathering enough usable tracks to work on.

Yet, these all are just base maps needing constant updates, having no information on current traffic data. For this latter, other, more sophisticated techniques are needed. Let’s take a look at some of these approaches:

Starting with the statistical approach, when previously collected and analyzed traffic patterns are attached to each road. With this incorporated traffic flow data, the routing algorithm can do better time estimates for the possible routes. Even though this approach gives a better route, it still didn’t solve the problem of keeping its data up-to-date.

Being up-to-date necessitates an interface to refresh data. The online service approach solves this by having a central hub that constantly collects traffic data from various sources (traffic surveillance and control systems, or sampling a subset of cars also known as Floating Car Data), and sends updates to subscribers through some wireless medium, typically over a cellphone data network. Such systems can provide information on traffic events minutes or even hours earlier than radio news, saving precious time for their users.

However, not all types of traffic data needs a central database. The decentralized version of Floating Car Data uses traffic information collected from neighbouring cars in an ad-hoc network fashion. In this scenario, cars broadcast their position, direction, velocity and other traffic information, as well as relay data from cars ahead, and filter data broadcasted by other cars for relevance. The strength of this approach lays in its adaptability to spontaneous short term situations, e.g. assisting drivers to cooperate for driving safety. In the same time it may also provide enough data for making longer term decisions, such as choosing a better route.

These advanced systems are still mostly lay on the drawing boards, and are still too expensive to become widespread. However, with the recent trend of car manufacturers (e.g. Toyota, GM, and others) equipping all new cars with GPS receivers, the location and velocity data will be available from more and more vehicles on the move. At the same time, ad-hoc wireless networks also getting more of a commodity, it seems finally things are getting in place for distributed, always up-to-date, cheap and reliable navigational systems to appear in the near future.

Better be soon, as driving safety is also more and more of an issue as people rush towards their goals with an ever hastening pace, and they need to be guided, not further confused by navigation systems.