Route algorithms: MapSource - V - 2610

From: Reg (news_at_g4ens.fsnet.co.uk)
Date: 11/26/04 

Date: Fri, 26 Nov 2004 23:09:25 -0000

I am having problems with the route algorithms in both MapSource
5.2/ECN 6.00 and my 2610, V-3.50; or is it the mapping data sets?

I am experienced with GPSrs, as the 2610 is my third Garmin having
bought a 75 in July 1996 and connected with Psions & wintels for
moving map and waypoint etc management. I've also been in the PC
business for 25, before I retired, and have sold commercial programs
that I have designed and programmed. So I'm not a newby!

This week I produced 3 routes on my laptop for a day's three legged
driving. On the first route from home to the first destination, I
entered a via, to force MapSource to take a different route to avoid a
known traffic congested road at that time of day. The main part of
the route was to the east and at the via changed to a s-w direction.

On approaching the via point, I noticed that the route purple line
branched into two lines. I followed the indicated route, which I knew
quite well, without difficulty, but the other purple line was
straight.

I soon realised that I would be late arriving, having found that the
indicated arrival time has been quite good.

As I got closer to my destination, I saw that the straight line went
to the destination, but the arrival time was very late and I realised
that I was on time. At the destination, the route navigation
continued, probably back in a straight line to the via point. I
assumed that when I added the via point I had left it after my
destination. But on returning home and looking at the route with
MapSource, I had not made any error.

Has anyone seen this before?

I also noticed as I left home that the 2610 wanted me to take a few
narrow roads before joining the main road a few miles away. This
would add an extra few miles to the journey rather than using the
close main road by the shortest distance and with wider roads. I have
seen this many times and just took my normal route, so got a
'recalculating' message.

As I proceeded along the main road the 2610 kept telling me to turn
left or right off the main road. Now why does this happen? (see my
set options below)

The main road is shorter and faster and I have not set any road
'avoids'. I have found this odd behaviour many times and has caused
me to loose confidence in it's ability to provide good routes.

So on the third route, getting closer to home, I decided to follow the
given route to see which way it took me. As I left the main trunk
road, I would normally travel on one main very straight road for 8.9
miles (using MapSource) and then turn off for another 0.5 mile to
home.

I was sent on a twisting route along narrow single tack roads much of
the time. A distance of 14.5 miles. I have the OS 1:25,000 map of
this area which I know very well, but I was sent along single track
roads that I've never used before. Fortunately I drive a Land Rover
4x4. At many junctions I knew of a shorter and therefore faster way
home but continued to follow the indicated navigation.

Back home I checked the routes planned in MapSource and uploaded to
the 2610. The strange route I was sent on by the 2610, was not the
same as uploaded. This had only one 'diversion' off the main road.
The route followed was not recalculated, so why does the 2610 change a
route calculated on MapSource.

I can accept that the algorithm used by the 2610 is different to the
algorithm in MapSource, especially as the preferences are completely
different in each case.

I have also found that I am often directed onto unsurfaced roads that
are sometimes not legal roads for vehicles - I have a number of years
of experience with British Rights of Way and their legal use by
vehicles and know the history of many of these local rights of way.

I've also in the past been sent along 3 sides of a square of roads
rather than just using a single side of that square. Directing me
into a residential area rather than staying on the main road.

I use custom, best route, major roads 10 - prefer, medium 4, minor 1-
avoid; on the 2610. I use faster time, car/motorcycle, avoid road
tolls, speeds 58,58,40,30,20 mph in MapSource.

The algorithms or map data must have major errors. I am well aware of
the fact that data sets have numerous errors in the road information,
but this is much more than I've noticed in using computerised mapping
data sets for over 8 years.

Anyone any thoughts on solving these types of problems. I am on a
number of lists and too many folk are reporting similar problems.

Reg.

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