Cycling UK Forum

I have an early Garmin E-trex and enjoy doing local sportives. I have found that the organisers websites provide GPS data files for most events these days. The problem is that these files are too large for my E-Trex to accept. Has anyone else found this? I would like to buy another one but having looked into this a little, I have discovered that all but the most expensive units are unable to accept such track files. I do not want the device to act as a HRM or cycle computer, I merely want to be able to load in trackfiles from websites etc and use it to navigate me around without having to consult a map or route sheet. Can anyone advise me what devices the organisers expect people to use and what would be best for me?

I have a Garmin Etrex Venture and have seen this problem Use Garmin software such as City Navigator or Track logs split into Chunks . Can the basic etrex store routes as this is a neater solution. Use something like city navigator to build your own version as a route rather than a track. you can also upload tricky junctions as tracks so whenever you come across a dificult junction The breadcrumb trail gives a visual picture of the junction

The old Etrex had twice the number of track points available in a track compared to my new Etrex HCx!
If it is a track log then an alternative to splitting tracks is that most of the mapping programms will have an ability to reduce the number of trackpoints in a track (in an intelligent way so they remain quite useful as tracks)
So I reduce to 500 points per track but on the old Legend I could have 1,000 points.

Rather than buy a new GPS that you do not really need, I suggest you pay a fraction of that for a really good piece of software capable of boiling down any track to a more sensible number of points.

My preferred utility for this is GPSU, as it knocks out only the least vital trackpoints. It does this on the basis of how far off-track the wiggly line will stray, compared to the original track, when those trackpoints are deleted. You can tweak the off-track distance and I generally find that something like a 20m off-track tolerance gets the number of trackpoints down to under 500 for 100km of wiggly lanes.

Since Garmin GPS units are far and away the most commonly used by cyclists however, it's a bit daft for all of you to be doing this independently!

Next time you find that the organiser has published a track with more than 500 trackpoints, I suggest you quickly and politely request that it's amended at source!

So judging from the replies so far, am I to assume that there isn't a unit on the market that will do what I want it to do? If money were no object, is there nothing out there designed to cope with what I feel is such a basic operation?

My present garmin E-Trex will only upload 125 trackpoints, which when I reduce the number of trackpoints to that, accuracy is seriously compromised, making it next to useless really. Apparently it uses a different part of the memory to record tracks than to store them, thus giving the situation where a track that has been created on it and saved on memory map cannot be loaded back into the GPS.

I have a magellan triton 400
http://www.magellangps.com/products/product.asp?segID=425&prodID=1913
Obviously I have the european version, currently available for around £150 at a few places online. If you want the bike mount ( a bit of plastic ) that costs about £30 though.

One of the routes I have on this unit has 1497 waypoints and covers 415 miles ( from Malmo to Stromstad in Sweden ). I think the unit is limited to a maximum of 20 routes but it's been a while since I've used it and can't remember.

The downside of the magellan units is availability of maps, there's basically nothing for europe that's recent. I have been using Mapsend Direct Europe v2 which is now several years out of date and was produced for an older magellan unit ( the meridian ). The only problems I've had with the outdated maps is where new roads have been added since these maps were created and these have, so far, always been new housing i.e. not roads of any significance ( unless you happen to live on one or are trying to get to one although google maps solves this problem ).

Since the 400 accepts an sd card ( the 200 and 300 don't ) I've got maps for most of Europe on a 2GB sd card.

To date the gps has travelled over 4000 miles mounted on my handlebars through all kinds of weather and has yet to give any problems although looking in some forums others have had problems with theirs. The problems mainly appear to be when connecting the gps to a computer, many computers don't seem to be able to communicate with the gps reliably. Magellan may have solved the issues but as I said I haven't had occassion to use mine for a few months....

I'm also inclined to agree that you should try down-sampling the GPX files before spending money on a new GPS. There's some interesting information on what the limits really mean, although I haven't entirely got my head around it myself.

Other programs with down-sampling functions include GPSBabel, GPS TrackMaker and WinGDB3, of which I'd probably try the latter first.

It's also worth chatting to other entrants on this forum and others, as someone else may have done the conversion.

You could also try splitting the downloaded route into several smaller routes. This would require you to load the next route as you complete each route on the gps but does avoid the expense of a new gps

A quick google:
http://www.routeconverter.de/features/en

I'm sure there are others available.

If the downloaded route is a gpx file it's possible to split this into different routes using a text editor ( e.g. windows notepad ) but this does require some xml knowledge.

Edit:
WinGDB may have a split function as well. This could be a better bet than routeconverter since WinGDB has a recommendation from drossall, I haven't used either of these programs....

From the WinGDB site
Changes 21-05-2009 (3.42):
- New and improved filter/split functions
- Splitting now for tracks too.
- Fixed bug with route color and notes

Should say I am not an expert and am still playing with these programs.

At least you have had some experience with the programs, I have absolutely none.

This makes you more of an expert than me

Why does memory map come into it? My Garmin eTrex Legend HCx came supplied with MapSource software, which I think is standard. You can filter a .gpx track to less trackpoints in MapSource with Track Properties / Filter.

I'm not familiar with the old eTrex but I'd say that a GPS unit that can handle only 125 trackpoints is pretty useless nowadays.

SCH wrote:My present garmin E-Trex will only upload 125 trackpoints, which when I reduce the number of trackpoints to that, accuracy is seriously compromised, making it next to useless really. Apparently it uses a different part of the memory to record tracks than to store them, thus giving the situation where a track that has been created on it and saved on memory map cannot be loaded back into the GPS.

If you're using Memory-Map to reduce the number of trackpoints, I'm not surprised that the result is useless.

Memory-Map goes about this task in a very simple and stupid way: it simply knocks out every second trackpoint, regardless of whether it's in the middle of a straight section of road (where its loss will not be noticed) or marking a corner, where its loss will divert the track so it cuts the corner.

The other day in the CTC office we tried using Memory-Map to reduce a 100-mile ride to under 500 points, and some corners got cut by as much as a quarter of a mile! Had we continued the process to fewer than 125 points we should have been out by more than a mile in places.

Like I said before, GPSU is much cleverer than that. Although 125 is an awful low trackpoint limit, I'm confident that GPSU would condense a 100km route to such a number and still not be more than 50m off-track. That's near enough, I think you'll find. Tell you what: I'll PM you my home email so you can send me one of your indigestible tracks, which I'll send back "boiled down" to 125, for you to check that out.

But all considered you would benefit from a new GPS: one of the better Etrex or Edge models. They'll still not accept more than 500-point tracks, but almost every other participant in those events will be subject to an identical limitation, so any clued-up organiser will have adjusted the available download accordingly.

CJ wrote:Rather than buy a new GPS that you do not really need, I suggest you pay a fraction of that for a really good piece of software capable of boiling down any track to a more sensible number of points.

My preferred utility for this is GPSU, as it knocks out only the least vital trackpoints. It does this on the basis of how far off-track the wiggly line will stray, compared to the original track, when those trackpoints are deleted. You can tweak the off-track distance and I generally find that something like a 20m off-track tolerance gets the number of trackpoints down to under 500 for 100km of wiggly lanes ...

I installed the Freeware version. This accepts a track with up to 500 trackpoints. However, I'm finding the filter tool hard to fathom. I haven't managed to filter a 500 point track down to a lower number of trackpoints. Ideally, you would be able to open a track and filter it down to a chosen number of trackpoints. If this utility can do that, I haven't found the method.

drossall wrote:[...]There's some interesting information on what the limits really mean, although I haven't entirely got my head around it myself. [...]

Seems to me that people will be in deep confusion until they grasp the difference between a track and a route. A track being a record of where you've been, a route being information to tell someone where to go.

So to create track data, you get out on your bike and let your GPS device record where you have been. That's far more information than another cyclist needs in order to follow in your bike tracks.

On road, to describe a route all your GPS navigator needs is 1) to remember where roads are 2) infrequent route points, say 10 for every 100 km. But if your navigation device doesn't store the location of roads, more route data is needed. But not much. Just a routepoint after each junction.

Off road more data is needed to describe a route.