Living with a Garmin: Three Ways to Beat the 500 Trackpoint Limit
If you construct a track of more than 500 points, when you upload it to the GPS it will be truncated, and any points after the 500th will be lost.
This is quite a severe limitation, since typically on a bicycle 500 points only represents about 30km.
Method 1 - split the Track
The simplest way round this is to divide the track into 2 or more sections, each of 500 points or fewer. Provided you stay within the GPS total tracks limit (usually 20) then you won't notice any difference on the road.
You have to make sure each track you upload is set to 'show on map' of course.
Method 2 - downsample the Track
Another way around the problem is to downsample the track. Many software programs can do this. Mapsource and Memory Map can both do this job via the track properties dialog. GPSBabel can do it too.
They use a very clever algorithm so that in practice a track downsampled from, say, 2000 points down to 500, still manages to maintain a good shape and especially at any sharp changes in direction.
Method 3 - utilise the Active Log
This method is something of a curiosity, rather than being all that practical - the other 2 methods are usually preferable.
Construct your track, of any size up to 10,000 points, and then in Properties rename it to exactly this:
Then upload it using Mapsource as usual. This works, for one track only, up to a limit of 10,000.
It appears on the GPS as the 'recorded' track, and not in any of the 20 slots reserved for uploaded tracks. You can still use the setup menus to colour it so it highlights on the map.
Of course, as you start to travel, you will add points onto the end of this 'recorded' track. When it hits the limit of 10000 (or whatever is set in the Garmin), you will start to wipe existing points. You should make sure, in the Track Log Setup menu, that it is set to Wrap when full (which I think is the best choice anyway, for general use). This means that, if you are following your uploaded track, any points that are erased will be behind you, and in fact you will already have laid down a replacement recorded track over that section. Although points are being wiped, they are points you don't need anymore.
Some basic stuff:
Living with a Garmin: Etrex Basic Setup
Living with a Garmin: Battery Runtime and Etrex Jitter
Living with a Garmin: The Waypoints Limitation
Living with a Garmin: The Follow Road Trap
Living with a Garmin: The Circular Routes Problem
Living with a Garmin: Declutter the Page Sequence
Living with a Garmin: Living with Metroguide Maps
Living with a Garmin: Waypoint Naming (for direct-style routes)
Living with a Garmin: Colour your Tracks and Routes
Living with a Garmin: Create a Route on the GPS
Top 5 GPS Tips (pdf) reprint of Arrivee article published Feb 2007
Some GPS FAQs web version of Arrivee article published Nov 2008
NEW - Garmin Etrex 20/30 essays:
Etrex 30 review reprint of Arrivee article published Jan 2012
Etrex 20 & 30, Basic Setup
Taming the Etrex 20/30: Restore the 'Page' key.
Dakota 20 review reprint of Arrivee article published Feb 2010
Living with a Garmin: Waypoint Naming and the Dakota 20 / Etrex 30
More Garmin essays - not-so-basic:
Garmin Etrex C Menu Map (pdf, July 2008)
Living with a Garmin: Full Reset
Living with a Garmin: Track, Route or Autoroute
Living with a Garmin: Three Ways to Beat the Waypoint Limit
Living with a Garmin: Three Ways to Beat the Trackpoint Limit
Living with a Garmin: Less is More
Living with a Garmin: Add Contours to your GPS Maps
Living with a Garmin: Struggling with GPX &... More GPX
Living with a Garmin: Screens you don't see every day
Living with a Garmin: Downgrade your Mapsource
Living with a Garmin: Put an OSM Map on your Garmin
Living with a Garmin: GPS Soak Test files to test your GPS waypoint capacity
OpenStreetMap and Mapsource Add OSM to your Mapsource collection
A Google Maps Workflow Create, Edit, Save, Share and Export a route