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How TomTom Make Maps - Part 1: Map Geometry

Part 1 : Map Geometry
Part 2 : MapShare
Part 3 : IQ Routes
Part 4 : HD Traffic
Part 5 : Map Changes

Article by: Mike Barrett on 21Aug2012

 

This is the first in a series of articles that examines the intricacies of creating and maintaining digital maps by TomTom. This article looks at the Map Geometry, how the roads are discovered and the basemap created.

 

Essentially the TomTom digital map can be regarded as a series of layers, starting with the basemap defining the geometry of the roads, the next layer provides the map attributes (names, turn restrictions etc), then on top of that comes community contributed content, then we have the 'real road speeds' provided by IQ Routes, and then at the top of the stack is the TomTom HD Traffic.

 

The conceptual layers of a digital mapThese can conceptually be viewed as different components drawn on tracing paper and placed on top of each other. Each higher layer provides more information and adds more value to the layers below.

 

This is also true of what is called the basemap. This starts with the basic lines representing the roads, then the next layer identifies these roads with names etc.

 

Although we regard a road as a line the digital map contains no lines at all. The core of the map is just a series of points called nodes. The nodes have data associated with them, particularly the GPS co-ordinate to locate it. One of the other critical pieces of data is an association with another node or to put it more simply point A is connected to point B. However it is not as simple as that because point A could also be connected to point C forming a junction. From this we can see that the roads are just conceptual rather than actual. This is not particularly important as far as the end product is concerned, but is critical when you try to create a route. See the section on IQ Routes for more information.

 

Having summarised what a digital map consists of we now need to understand how these data are collected in the first place. Nowadays it is quite rare that a map will be created from scratch, but it is quite easy to see how it can be done. All you need to do is go out to the location you want to map and start collecting points. It is actually quite easy and anyone can do it just grab your GPS tracker and off you go... This will record a series of points for you and from that you will be able to draw a map.

 

This is all well and good, but a series of dots is not that useful other than a starting point to create your real map. Typically a tracker will save a point every few metres, but a road could be hundreds of metres long with no intersections so why bother saving all the intermediate points? This is where the TomTom map creation and management application comes to the fore. Called Cartopia it amalgamates a number of different data sources and can provide overlays to assist the operator in determining how to create the map elements.

 

There are many sources for the initial data, ranging from Local Authorities, National Planning and Mapping agencies (ie Ordnance Survey), driver feedback, MapShare, Satellite Imagery etc. TomTom consolidate 50,000 different Authourative Sources into the map database. All of these can provide information about different aspects of the map data which are combined to produce the map that is delivered to your SatNav device.

 

So getting back to basics the map geometry is the core component of a digital map. TomTom have a number of different ways to generate this input, the common means are: Local Authorities issuing plans of road changes; mapping van survey; and probe data.

 

The TomTom mapping van with GPS and cameras

 

One of the most important sources of new information is the TomTom mapping van. The TomTom Mapping Van is specially kitted out with cameras, Lidar sensors, gyroscopes, redundant computer systems, and of course very accurate Differential GPS. All of these devices record information to redundant hard disks providing georeferenced data to be processed back in the mapping center.

 

We are all used to using GPS for accurate locations, but there may be times when GPS is not available or reliable. The TomTom mapping van includes sensors on the wheels to determine the distance travelled, and a gyroscope to record the changes in direction of the van. This provides very accurate movement records which when combined with the GPS allows the mapping of underground road networks as well as carparks and other environments where GPS signals are challenged.

 

Our video below provides an overview of the TomTom mapping van with a quick on-board trip to show the sensors in action.

 

 

All of this information is fed into the Cartopia database and allows the operators to get almost as good a view of the surroundings as actually being there. The cameras capture images every 8 metres in the city and 10 metres on highways. With a view of 360 degrees all the signposts, roadside features etc can be viewed back at the editor's workstation. It should be noted that all the images taken are for internal use only so there are no privacy issues involved.

 

Cartopia includes image recognition software.

 

Now with six photos being taken every 8 metres you can calculate that over a stretch of road of 1Km 750 photos are taken. Assuming that a mapping van surveys 200Km a day you suddenly have 150,000 images per van per day to look through. This is obviously not practical so image recognition software has been utilised to pick out certain parts of images for example road signs. The software is programmed to recognise certain patterns such as speed limits. These can be automatically applied to the database.

 

Armed with this abundance of information the map editor can start working on the map. The basic geometry of the roads can be plotted in Cartopia. Cartopia is a bespoke application specifically written to provide the functionality needed to create and maintain the digital map data. At it's simplest it has basic CAD functions allowing the user to draw a series of lines and provide the ability to connect them together into a network.

 

To assist the editor in making the correct decisions the computer display can have a number of overlays applied to it. This is a little like adding different information on transparent tracing paper and compositing the sheets so that a view of all the images can be seen. A common base layer would be an aerial or satellite image, on top of this could be the GPS traces from probe vehicles, on top of this the GPS track, and at the top level would be the map details that are being worked on.

 

Thus it becomes easy to create an accurate map layout even without having a mapping van visit the location. Given a recent aerial photo of the new roads it is easy to draw the nodes and connect the dots, but the rest of the attributes on the road are less easy to determine. This is when the community input of MapShare proves its value. MapShare provides local expert input to correct map data.

 

TomTom MapShare is the subject of our next article in the series: How TomTom makes maps Part 2 : MapShare.

 

 


References

Manufacturers Web site http://www.TomTom.com
Pocket GPS Contributor

Mike Barrett

   
Forum Comments:

 

Comments
Posted by dorsetwurzel on Thu Aug 23, 2012 4:41 pm Reply with quote

Very interesting article. Looking forward to the next one. Very Happy


 
Posted by jonrome on Fri Aug 24, 2012 8:21 am Reply with quote

It would be great if someone could produce a way to convert present day maps to th run on the thousands of Alpine systems installed by Jaguar up to the the late 2000s. Absolutely no support.
A disgraceful state of affairs for a company like Jaguar who appear to be proud of their heritage but really only want to sell you a new car.


 
Posted by Surfing_spider on Fri Aug 24, 2012 9:35 am Reply with quote

Great Article. I really like getting to know the details of exactly how these systems work.

What I really want to know is why the junction priorities are wrong so often. i.e. when you are driving along a road and it tells you to take a left turn but this is just a natural continuation of the road. There does not seam to be a part of mapshare that allows you to correct this. I am eager to help fix these issues but can't.


 
Posted by Daggers on Fri Aug 24, 2012 9:52 am Reply with quote

Surfing_spider Wrote:
What I really want to know is why the junction priorities are wrong so often. i.e. when you are driving along a road and it tells you to take a left turn but this is just a natural continuation of the road. There does not seam to be a part of mapshare that allows you to correct this. I am eager to help fix these issues but can't.

I'm with you on this one - you can just about work it out if it tells you to turn left when the only obvious straight-on route takes you up a farm track, but if you're in a built up area and told "in 400 yards, take the 3rd left" it gets a whole lot more confusing.


Garmin DriveSmart 50 LMT-D

 
Posted by cbrown7 on Fri Aug 24, 2012 2:05 pm Reply with quote

I'm with Surfing_spider and Daggers on this one. Plus, why on UK back (B) roads do Tom Tom's often not alert you at all to cross roads you have to give way at? I know it is up to the driver to interpret the road and drive to the conditions etc. but you do tend to get lulled into a false sense of security if you have no warnings of impending actions.

I can't believe this is down to priority changes as most of these roads have been there for years, with little traffic, so why would they change?

Great article by the way.


 
Posted by pillboxman on Fri Aug 24, 2012 2:52 pm Reply with quote

Great article. Thanks.

My guess would be that the 8/10 meter 'spots' on the roads is the reason that the on screen mapping is so much better on a TT than a Garmin.

As well as speed cameras I use my TT to help me drive more economically. I can see the road ahead and slow down or speed up depending on the bends in the road. This saves tire wear, fuel and brake pads!

Oh, and it's great at navigating as well. Laughing


 
Posted by MikeB on Fri Aug 24, 2012 4:44 pm Reply with quote

pillboxman Wrote:
... My guess would be that the 8/10 meter 'spots' on the roads is the reason that the on screen mapping is so much better on a TT than a Garmin. ...
The 8 or 10 metre bits only refer to the imaging so a picture is taken and geo-referenced at those intervals.

Typically there will be far less points in the map as they are simply not required. A road is normally pretty straight for long distances so additional points are only required at junctions.


Mike Barrett
Editor, PocketGPSWorld.com

 
Posted by Stormtracker on Fri Aug 24, 2012 5:58 pm Reply with quote

If TomTom go out-and-about in their "car derived van" doing some of the mapping, then surely they can create a section in the menu for vehicle types: Such as-

Are you driving a Car, Large Goods Vehicle etc. So it can route narrow or wide roads only.

Because I am sick and tired of approaching an "Unnamed Road", or "B" road slowing down and thinking, yes this is wide enough for me and another vehicle to pass without problems. To get half way down this road, to find that it narrows alot and that my Large Goods Vehicle is actually wider than the road and I am stuck facing an oncoming vehicle - obviously using a TomTom too.

and another thing - "Turn-a-round when possible". lmao, you try turning round a 7.5tonne flatbed truck on an urban road.

Sometimes, I just want to put my "TT820go live" under the front wheels and say Route This.

Excellent article by the way. However, if TomTom use all this technology, why are their maps still upto 1 year out of date?


 
Posted by pillboxman on Fri Aug 24, 2012 6:26 pm Reply with quote

Stormtracker Wrote:
If TomTom go out-and-about in their "car derived van" doing some of the mapping, then surely they can create a section in the menu for vehicle types: Such as-

Are you driving a Car, Large Goods Vehicle etc. So it can route narrow or wide roads only.

Because I am sick and tired of approaching an "Unnamed Road", or "B" road slowing down and thinking, yes this is wide enough for me and another vehicle to pass without problems. To get half way down this road, to find that it narrows alot and that my Large Goods Vehicle is actually wider than the road and I am stuck facing an oncoming vehicle - obviously using a TomTom too.

and another thing - "Turn-a-round when possible". lmao, you try turning round a 7.5tonne flatbed truck on an urban road.

Sometimes, I just want to put my "TT820go live" under the front wheels and say Route This.

Excellent article by the way. However, if TomTom use all this technology, why are their maps still upto 1 year out of date?


Have you considered purchasing one of the HGV PNV's? You can put it against your tax.


 
Posted by DennisN on Fri Aug 24, 2012 9:51 pm Reply with quote

cbrown7 Wrote:
I'm with Surfing_spider and Daggers on this one.

[snip]

I can't believe this is down to priority changes as most of these roads have been there for years, with little traffic, so why would they change?

Great article by the way.

The reason for all these funny instructions is TomTom have reduced the details on some "roads", presumably for space constraints on mapping. Compare these two screendumps taken from two devices, running side by side, but with different map versions - the first one is an older map, second a more recent one.





Now for side roads.. Here are two views of the same spot. The first picture is from my ancient map (2006-ish?), the second and third are from the current map which instructs me to turn left or right at this corner. Notice that in the older map, the offshoot "roads" used to have the purple dots which denote non-navigable roads. I regularly get exactly the same from laybys - instructed to keep right (and not go into the layby). No doubt the savings allow TomTom to add value, like facebook and twitter links! And avoid the need to increase the size of the device's internal storage. A few months ago, in North Devon, I was instructed to turn right when the straight ahead alternative was over a stile and along a green lane filled with weeds four feet high!






Dennis

If it tastes good - it's fattening.

Two of them are obesiting!!

 
Posted by Stormtracker on Fri Aug 24, 2012 11:37 pm Reply with quote

[quote="pillboxman

Have you considered purchasing one of the HGV PNV's? You can put it against your tax.[/quote]

Hi Pillboxman,

I only bought this TT820 back in April this year, as I was using it mainly for my car and occasional driving when one of the drivers was on-leave/off-sick at work but in the past couple of months, I am now one of the permanent drivers and I have found how useful my TT really is. TT's PNV's are only good for Car Navigation and (expletive) for Truck use.

Yes, I have been looking at a Snooper Truckmate and I may have to purchase one of these before I lose my insanity or drive over my TT - which ever comes first Laughing Out Loud.


 
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