The Garmin
marine market and
outdoor market (hiking, orienteering, geocaching) GPSR's all have a software feature that allows the user to track back along the path they followed in the first place. This is called (not surprisingly) "Trackback".
The Garmin
automotive market GPSR's don't offer an exact trackback feature, because doing an exact trackback would bring the user into conflict with traffic coming down the road in the other direction. There is also the problem of one way streets, motorway ramps, traffic circles, and so forth. So, I think you can appreciate why this capability is not provided on the automotive units.
There has been discussion in the past about providing some kind of utility within MapSouce - the application you use to view tracks you have created on your GPSR - to somehow allow MapSource to convert a track to a route. This isn't really a "top shelf" priority with the software engineers who develop MapSource, because the users who are really familiar with using MapSource and creating routes can accomplish the same thing pretty quickly right now, with MapSource 6.1, by a series of mouse-clicks to create a string of sequential waypoints over a track line at key points (turns). The 6.1 version of MapSource allows any route to be inverted, the inversion will not give you an exact opposite direction route, because it will obey all the traffic laws as it creates an opposite direction route that follows the roads originally used as closely as possible. I think this is what Bob Jeffries was referring to in his reply posted above.
There are some utility programs available free of charge that have been created and put in the public domain by third party enthusiasts that allow tracks to be converted directly to routes, and routes to tracks. The problem with these is that they tend to work only with specific models of GPSR's, typically, the non-automotive ones.
I have had unintentional first-hand experience with an automotive GPSR that provided an exact track-back feature, and it wasn't a pretty sight. This happened when I was testing early generation software on a recently released model of GPSR. It was really, really confusing to be presented with exact track-back guidance instructions that violated traffic laws. Needless to say, this snag has since been fixed.
Dual-sport riders are sometimes caught between two worlds - there is a desire to have the GPSR on the moto behave occasionally like a marine or hiking unit, supporting exact track back, but most of the time, the desire is to have it respect traffic laws.
"Horses for Courses" was the wise comment made by Richie last time this topic came up. Meaning, if the trackback capability is very important to you, you have three possibilities:
1) Buy a marine unit that also does automotive navigation (e.g. 276C), but accept that there are some disadvantages associated with that if you are using it primarily for automotive work (small map memory capacity, not all the software tricks of the pure automotive units are available for road and route control), or;
2) Buy a pure automotive unit if that is what you think your primary use will be, then buy a very inexpensive "outdoor" model handheld GPSR, with no maps in it, to use for trackback purposes. This will cost you about $ 80, new.
3) Adjust your automotive unit (SP III or SP 26xx) so it displays the track log points you have created on the screen, then manually follow the breadcrumb trail back when you need to return.
If you just want a device that will maintain one huge, unlimited track log that shows where you have been, without over-writing it as the SP's do after a while, you can buy such standalone devices for far less than the price of an automotive autorouting GPSR. Or, you can simply turn off the track log recording feature of the SP at the end of your "interesting" track, so it won't overwrite it until you get to a computer to download and save it.
Another possibility: Buy a cheap used laptop (mine cost $300), and put it in the pannier. If you want to save data from the automotive GPS, or upload a new route, or change maps, etc., while on a long trip, just pull out the laptop.
This topic has been kicked around a great deal (beat to death, in fact) in the past few weeks, in addition to the thread that Garfieldus mentioned in his post above, there are discussions of the same topic in these two threads as well:
Gamin 276
and
GARMIN GPSMAP 276C Any good? Where to get one?
PanEuropean
