Garmin Trip Planner, why won't it follow the defined route?

[Colorado Jeff]

Hi Everyone:

 

Last February I read how to create a route on Google maps, save it as a KML file, convert to GPX, transfer to microSD, which then shows in the Tracks app on our Navigator VI.  From there you convert it to a Trip, where it now shows in the Trip Planner app. 

 

When I activate the route I want on the Trip Planner app, the map of the route I defined shows, but more often than not after I select "Go", Garmin will change the route I defined.  I know that I have "Fast" route selected as a preference, but the other options would change the defined route too.  Garmin support does indicate that their device will follow a defined route on Trip Planner, but not much more info.

 

I have created a number of very specific routes that maximize mountain passes, river valleys, and scenic byways leading from one mountain city to the next.  With all these combinations, I can create any number of multi day trips around Colorado.  So I'm not looking to change my routes if someone was inclined to suggest I follow Garmin's sage advice.

 

Thoughts on possible solutions?

 

Thanks

[Bernie]

I don’t have a tested method on how to use Google routes with Garmin GPS units.

The best way I have found of making a Route from a Track is using BaseCamp. But It is complicated and time consuming procedure.

But you the following procedure should work on your GPS.:

Import the GPX file from Google. You said this will give you Tracks?

If you use the GPS to create a Route from a Track, it will provide you with only 2 points, the Start and the End.

You have to remember 2 importing things.

First you must tell the GPS to start the route (Go too) at the First point, even if you are already at that location.

Second you can not let the GPS recalculate the route. 

With this in mind, change your settings to not recalculate the route. 

The other thing I would do, is to make the Tracks visible on the map, by using the Track App.

Select the Track, that matches your Route in the Track App, click on the 3 dashes and select show track on map.

Then select color of track and select either green, red or blue.

Your GPS does not change or alter imported tracks. By displaying the track of the route and the Route, you can make sure you are riding the original designed route from your Google maps, even if your GPS should alter the route.

 

[Colorado Jeff]

2 hours ago, Bernie said:

 

The best way I have found of making a Route from a Track is using BaseCamp. But It is complicated and time consuming procedure.

Thanks, but I've tried BaseCamp and the learning curve is ridiculously stupid and, as you say, it's time consuming.

2 hours ago, Bernie said:

But you the following procedure should work on your GPS.:

Import the GPX file from Google. You said this will give you Tracks?

If I put the GPX file on the microSD, insert the microSD into the Garmin/VI, the GPX file/route will show using the Tracks App

2 hours ago, Bernie said:

If you use the GPS to create a Route from a Track, it will provide you with only 2 points, the Start and the End.

When I convert the selected route in the Track App to a "Trip", it then shows in the Trip Planning App.  When I select the route, it shows the map of the route I defined.  It does not provide just two points; start and the end and it does not stay on the defined route.

2 hours ago, Bernie said:

You have to remember 2 importing things.

First you must tell the GPS to start the route (Go too) at the First point, even if you are already at that location.

Yes, that is what I am doing.

2 hours ago, Bernie said:

Second you can not let the GPS recalculate the route. 

That's what I am trying to not let happen!!!!

2 hours ago, Bernie said:

 

With this in mind, change your settings to not recalculate the route. 

How????  That is my question!

2 hours ago, Bernie said:

The other thing I would do, is to make the Tracks visible on the map, by using the Track App.

It is visible.

2 hours ago, Bernie said:

Select the Track, that matches your Route in the Track App, click on the 3 dashes and select show track on map.

Then select color of track and select either green, red or blue.

Your GPS does not change or alter imported tracks. By displaying the track of the route and the Route, you can make sure you are riding the original designed route from your Google maps, even if your GPS should alter the route.

But it is changing the route!  That is the very question I am asking; how do I get the GPS to STOP changing my defined route

2 hours ago, Bernie said:

 

 

[Michaelr11]

1 hour ago, Colorado Jeff said:

But it is changing the route!  That is the very question I am asking; how do I get the GPS to STOP changing my defined route

 

Which Garmin GPS are you using?

 

Every Garmin GPS that I have used has an option in the settings for recalculation.  The choices for the option are usually, Automatic, Prompted or Off. 

Try looking in Settings for Navigation or Routing.  Then look for Off-Route calculation.  Sounds like yours is set for Auto-Recalc.

 

[Colorado Jeff]

8 minutes ago, Michaelr11 said:

 

Which Garmin GPS are you using?

As noted in my original post, the Navigator VI

8 minutes ago, Michaelr11 said:

 

Every Garmin GPS that I have used has an option in the settings for recalculation.  The choices for the option are usually, Automatic, Prompted or Off. 

Try looking in Settings for Navigation or Routing.  Then look for Off-Route calculation.  Sounds like yours is set for Auto-Recalc.

You are correct Michael, it is set to "Automatic".  When I read Garmin's description of "Off-Route Recalculation" it's purpose is to get you back onto your defined route if you stray away from it.  I'm simply trying to get the Nav VI to follow the defined route I created and to stop changing it.  If I was to stray from my defined route, I would actually like it to take me back to my defined route.

 

The question is how do I get the Nav VI to stay on my defined route?

 

8 minutes ago, Michaelr11 said:

 

 

[MikeB60]

Without either way points or shaping points in the Google maps routes, I'm not sure you will get the desired results. Base camp is a pain to learn but that's the only way I've been able to get the routes to match up when transferring to the Nav VI.

[dirtrider]

1 hour ago, Colorado Jeff said:

 

The question is how do I get the Nav VI to stay on my defined route?

 

Afternoon Colorado Jeff

 

Without matching maps in whatever you originally make the route on & what is in your GPS then getting matching routes is a real crap shoot. No matter what, if the imported route doesn't match the map inside you GPS then it will recalculate (no matter if recalculate is turned off) as it needs to do that so the routing follows the roads.

 

I have had some luck with importing (mis-matched map)  routes on older Garmin devices by importing them into the GPS with the GPS set to direct routes, THEN after importing,  switching to follow roads   (not sure it that is an option on your Nav vi).

 

On major roads with little option to route elsewhere then you can get a non matching map route to work most of the time. But when routing over smaller very specific roads then getting an exact routing map into a Garmin GPS is pretty iffy. 

 

I know you think using Base Camp is a pain but with a little playing, a little learning curve you will be WAY farther ahead in getting very specific, technical, functioning routes into your GPS that gives you exactly what you want routing & road wise. 

 

Just start using Base Camp, as you run into a road block just post the problem here & we can talk you through the resolution as some of us have been making very technical routes that track perfectly since way before Base Camp was even available (back from the pre-Base Camp Map Source days).

[Colorado Jeff]

1 hour ago, dirtrider said:

 

Without matching maps in whatever you originally make the route on & what is in your GPS then getting matching routes is a real crap shoot. No matter what, if the imported route doesn't match the map inside you GPS then it will recalculate (no matter if recalculate is turned off) as it needs to do that so the routing follows the roads.

Hi dirtrider:

 

When I load my defined routes in the manner I've described above, and I select it in the Trip Planning App, it gives an option to see the route on the map.  When I do that, the route I have defined shows correctly.  It even starts navigating correctly, but at some point it changes my defined route.

 

[Colorado Jeff]

1 hour ago, MikeB60 said:

Without either way points or shaping points in the Google maps routes, I'm not sure you will get the desired results. Base camp is a pain to learn but that's the only way I've been able to get the routes to match up when transferring to the Nav VI.

 

Hi Mike:

 

I used way points to define the routes.  The routes load correctly on the Nav VI, it's just that the Nav VI decides to reroute to another route with the same destination.  For example, instead of going to the mountain pass I want to ride, it will try to take me on another route to a nearby highway or a freeway.

 

Jeff

[dirtrider]

29 minutes ago, Colorado Jeff said:

Hi dirtrider:

 

When I load my defined routes in the manner I've described above, and I select it in the Trip Planning App, it gives an option to see the route on the map.  When I do that, the route I have defined shows correctly.  It even starts navigating correctly, but at some point it changes my defined route.

 

Afternoon Jeff

 

I'm not really sure what is happening but for some reason your GPS doesn't like your imported route, either due to mapping differences, or GPS routing avoidances, or something?    Possibly your GPS is set to fastest time, or avoid something, or you have avoid gravel roads turned on, & your GPS thinks there is a gravel section in that mountain pass (personally I turn off ALL avoidances then manually use (add) shaping points to force a route to go on those smaller roads or over sections they it won't naturally want to route through. 

 

A couple of things to do or look for__

 

First, when you load the route into your GPS make darn sure the you zoom WAY in then verify that it isn't trying to route on the wrong side of a divided hi-way. This will drive a route crazy  & usually force a strange off-route re-calculation. 

 

Next, once you load the route into your GPS (& it looks like it is what you want) save it in the GPS. That way if/when the route goes crazy you can stop the route, then re-initialize it, THEN see if will continue correctly on you intended route. (also drop a marker on your GPS so you can put your track (& marker) into BaseCamp then see what the heck went wrong & why it went crazy. 

 

You might also import the route into BaseCamp (that is a simple drag & drop) then you can go over the zoomed-in-route with a fine tooth comb to find where it is not working. Then hit re-calculate to see if it stays as you originally imported it, THEN upload THAT to your GPS (this should be a stable functioning route)

[BobW03]

Jeff, have you looked at this tutorial from New England Riders? Ed and a couple others have put a lot of effort into creating this and he is always willing to help users. All this is free. You can look up New England Riders on Facebook and join the group if you want, not limited to NewEngland. If you have questions about basecamp, I would suggest joining NER and then post on the group page.

 

https://www.newenglandriders.org/learn-basecamp/

Edited June 15, 2021 by BobW03
wrong initial link

[Colorado Jeff]

Thanks Bob

[Bernie]

3 hours ago, Colorado Jeff said:

 

You are correct Michael, it is set to "Automatic".  When I read Garmin's description of "Off-Route Recalculation" it's purpose is to get you back onto your defined route if you stray away from it.  I'm simply trying to get the Nav VI to follow the defined route I created and to stop changing it.  If I was to stray from my defined route, I would actually like it to take me back to my defined route.

 

The question is how do I get the Nav VI to stay on my defined route?

 

 

If you let the GPS recalculate the route automatically, it will change the route to the preferences you have selected in the settings menu of the GPS.

It also can only use the information you have provided it to calculate a route. When you use a track to create a route inside the GPS, it will make a route that matches the track, BUT the route will only have to points. A Start and a End point. It will have no WayPoints and no Shaping Points and no ViaPoints. SO if you get of the route by 1 Foot, the GPS will recalculate the route, using Your preferences (fastest or shortest routing) to the final destination. This has been designed by Garmin and you can't change that.

That is why we/I am telling you to change the settings in your GPS to not recalculate.

Changing this setting should keep your route as originally planned, even if you stray off the route. When this happens, you will have to find your way back to the magenta line, the Route on your GPS.

If you want your GPS to help you to find your way back to your route, you will have to provide your GPS with sufficient data for it to know where you want to ride or go. This is why I/We are telling you to use BaseCamp. When you create routes in BaseCamp, you insert into the route WayPoints and ShapingPoints. These points will tell the GPS that you want to ride on a particular road or path and also that you want to visit certain towns, sights or parks etc.

One option for all the BaeCamp haters out there is to use a Kurviger.de.

https://kurviger.de You can use this in different languages.

It uses a web site for creating routes. It lets you choose from different map data suppliers, including Google, Maps Me and others. It makes routes very similar to Google Maps. But you can safe them as routes and tracks. You can export these routes directly to your GPS or save the GPX files and transfer them later. It also saves the routes as Routes and Tracks. You can also use the routes created in Kurviger.de on your i-phones using Scenic and I believe they may have android version by now also.

But like with every mapping software, if you do not use points (WayPoints or ShapingPoints) to force the route onto the roads you want to ride, the software will use logic and direct you to your destination the shortest way possible.

I can highly recommend this website for anything to do with BaseCamp or Garmin GPS usage. Windows or Apple.

"You can look up New England Riders on Facebook and join the group if you want, not limited to NewEngland. If you have questions about basecamp, I would suggest joining NER and then post on the group page.

 

https://www.newenglandriders.org/learn-basecamp/"

Edited June 15, 2021 by Bernie

[Colorado Jeff]

16 minutes ago, Bernie said:

That is why we/I am telling you to change the settings in your GPS to not recalculate.

Please tell me how to change the setting in my GPS so it does not recalculate.   I can't find that option.

 

16 minutes ago, Bernie said:

Changing this setting should keep your route as originally planned, even if you stray off the route. When this happens, you will have to find your way back to the magenta line, the Route on your GPS.

Great!  This sound like what I want, I just don't know how to make it happen Bernie.

 

Thanks!

[dirtrider]

35 minutes ago, Colorado Jeff said:

Please tell me how to change the setting in my GPS so it does not recalculate.   I can't find that option.

 

Afternoon Jeff 

 

Look under __  Settings, then NAVIGATION, then CALCULATION MODE. Not sure what you will find there  on the nav vi but that is probably where it would be at. I'm not even  sure if the nav vi has a turn off feature for off-route re-calculation? 

 

Also, make sure that you have the latest GPS updates installed. 

 

 

[Bernie]

Here are a few screen shots from the BMW Navigator 6. I don't have a Nav4, but it should be similar. Hopefully Garmin and BMW used the same wording.

 

First select the Settings Icon (Wrench) from the home screen.

Then select "Navigation" from the next screen.

 

Select "Navigation"

Then select "Off-Route Recalculation"

 

Then select "Off" and "Save".

 

 

That should do it.

[lkraus]

I don't know if this applies in your case, but it's one other reason why your routes may be recalculating.

 

When you begin to navigate a route, the Garmin will display the starting point of the route, the end point, and any intermediate via points, and asks you to "Select next destination." Your NAV will then calculate a new route from your present location to the selected point, before following whatever remains of your pre-planned route. If you select the end point as the next destination, the entire original route will be ignored. 

 

Google is handy for initial planning, getting a quick idea of travel time, locating nearby lodging, etc., but for me Basecamp does a better job of getting the details of the route just right. Just the ability to use unannounced shaping points makes a big difference since I can follow an exact route without listening to a lot of warnings about upcoming waypoints.  If you give Basecamp another try, drop a private message to John Heath (jfheath) on this board and ask him to email you a copy of his guide on "Routing with Basecamp for the Garmin Zumos." He has done a lot of research into the interaction of the software with the GPS and has found out how to build routes that work the way you want them to. (Something Garmin has never done.)  The guide is written for the Zumo models, but the process works just fine with the Nav V and VI.

 

[Colorado Jeff]

1 hour ago, Bernie said:

Here are a few screen shots from the BMW Navigator 6. I don't have a Nav4, but it should be similar. Hopefully Garmin and BMW used the same wording.

 

 

 

Bernie, that is absolutely awesome of you to take the time to create and then post the shots of the process.  Thank you!  

 

As I understand it from the Garmin support, the "Off-Route Recalculation" is for how the GPS should respond when you have left the active route. 

 

I am looking to keep my Nav VI from altering my defined route.  Do you think changing the Off-Route Recalculation to "off" will prevent the Nav VI from altering my defined route?

[Colorado Jeff]

2 hours ago, dirtrider said:

Look under __  Settings, then NAVIGATION, then CALCULATION MODE. Not sure what you will find there  on the nav vi but that is probably where it would be at. I'm not even  sure if the nav vi has a turn off feature for off-route re-calculation? 

 

Hi dirtrider:

 

I have chosen "Faster Time", which could lead one to believe that this selection is overriding my defined route.  However, if I choose one of the other three choices, won't those over ride my defined route too?  Garmin specifically says in their description of using "Trip Planner" App that it is for defined routes.  If that is the case, then the Calculation Mode should not alter a route in Trip Planner.    Wouldn't be the first time a learning material like a support doc is out of synch with what a product really does I suppose.

[dirtrider]

13 hours ago, Colorado Jeff said:

Hi dirtrider:

 

I have chosen "Faster Time", which could lead one to believe that this selection is overriding my defined route.  However, if I choose one of the other three choices, won't those over ride my defined route too?  Garmin specifically says in their description of using "Trip Planner" App that it is for defined routes.  If that is the case, then the Calculation Mode should not alter a route in Trip Planner.    Wouldn't be the first time a learning material like a support doc is out of synch with what a product really does I suppose.

Evening Jeff 

 

It shouldn't cause the re-calculation but could effect how the route changes after a re-calculation. (you can get an auto recalculation (if turned on)  if even a small or short section of the route tries to route backwards on a one way road, or if the map that the route was made on doesn't perfectly match the one in your GPS. 

 

With "off-route" re-calculation turned off you can ride over those short things that cause a re-calculation & the route will usually not try to auto-re-calculate.    

[Colorado Jeff]

2 minutes ago, dirtrider said:

Evening Jeff 

 

It shouldn't cause the re-calculation but could effect how the route changes after a re-calculation. (you can get a auto recalculation (if turned on)  if even a small or short section of the route tries to route backwards on a one way road, or if the map that the route was made on doesn't perfectly match the one in your GPS. 

 

With "off-route" re-calculation turned off you can ride over those short things that cause a re-calculation & the route will usually not try to auto-re-calculate.    

 

Thanks dirtrider, I'll give that a go next weekend.  Appreciate all your thoughts on this subject.

[Bernie]

Jeff, the problem you have, is you trying to make a Route from a Track inside the GPS.

I know Garmin says you can do it, but they intented it to be used for Tracks that have been collected while riding with the GPS. 

When you do this, the GPS will make a route that matches your track. When you start navigating this route, everything is fine as long as you stay exactly on that route. If you deviate from that route and you have recalculation turned on, the GPS will not try to guide you back to the route, It will instead guide you to your destination.

This is the problem when trying to make a route out of a track inside the GPS.

That is why I suggested this morning, that you not just use the route (routes provide directions), But also display the track you have uploaded from Google Maps. The benefit of displaying the Track and the Route at the same time, is to provide you with your original designed route on your GPS display, even if it doesn't provide you with directions.

Tracks do not get recalculated. An imported Track does not change.

If the map data is different on the GPS than the map data that you used to create your original route/track, you may end up with a Track that is next to the actual road, but at least you will be able to adjust for that as your ride your route/track.

I believe the best thing would be to use a GPX converter, like GPS Visualizer to convert your Google Maps Routes to Garmin Version GPX files and then to import them into your GPS.

https://www.gpsvisualizer.com/

 

[Bernie]

I found this write up on how to use Tracks on your GPS units.

Maybe this would be of some help.

GPS-Tutorial-101-072618.pdf

[Bill Murray]

Jeff, there is also an excellent series of YouTube videos by Don Norwood that teach you how to use Basecamp. The video series is private, so you cannot discover it without a link to it. I found the series through a discussion on the BMW MOA forums a few years ago. Below is a link to a playlist of these videos. If the link does not work for you, let me know and I will publish the links to the individual videos in the series (34 in total).

 

https://youtube.com/playlist?list=PLAzqCfh_XhMat1SOOXwMYZ4i0MuV2Z0Io

 

 

 Personally, if I wanted a route based on the track you have exported from Google Maps, I would import the Track into Basecamp and create a Route within Basecamp. Then you could export that Route to your Nav VI instead of the Track or the route prepared through the Trip Planner. 

 

Another factor to consider is that the BMW Nav-series GPSs support a limited number of Via Points/Waypoints in a Route (if I recall correctly, 30 Via Points/Waypoints, including the Start and End points of the Route, and 125 Shaping Points between each Via Point, for a total 3750 points) to define your Route.

 

[dirtrider]

Morning Jeff 

 

You should really consider at least getting a little familiar with Base Camp, it has way more to offer than just making or transferring a route into your GPS device. 

 

For the most part it is not difficult to use once you understand the basics. 

 

On a problem like you are having now Base Camp has a playback option, that allows Base Camp to preview ride your route right on your computer screen.  It has a speed option from real time to x1000 (x100 makes longish routes go through fast but just slow enough so you can see if it is tracking correctly) 

 

You can just hook your GPS to your computer, import the route from your GPS into Base Camp then open the route, & pre-ride it on the computer screen. 

 

It helps to also have (or import) the track that you started with as you can overlay the imported route (from the GPS) over the original track to verify that they match EXACTLY,  then as you preview ride the imported route you can watch it follow the track to see if it does in fact follow the original track or deviate from it. You can then zoom WAY in to find &  understand  what went wrong & why it happened. 

 

Not 100% guaranteed to catch every problem but pretty useful at catching most. 

Added: I would also like to see how your Nav 6 converts a track to a route, most Garmin device conversions (including Base Camp) only give the conversion route a start & finish point (no intermediate via points). If the route is logical & straight forward then it can work with just a start & finish point, BUT, if ANYTHING goes  wrong (like missed turn, road isn't exactly matching the map data, small glitch, etc) the GPS will try to route you to the next via point best it can but with just 2 points on the converted route & the only one in the direction of travel that is the end of route point so the GPS won't usually put you back on YOUR route but just route you to the end point as the GPS thinks it should.  

 

[Colorado Jeff]

17 hours ago, Bernie said:

I know Garmin says you can do it, but they intented it to be used for Tracks that have been collected while riding with the GPS. 

When you do this, the GPS will make a route that matches your track. When you start navigating this route, everything is fine as long as you stay exactly on that route. If you deviate from that route and you have recalculation turned on, the GPS will not try to guide you back to the route, It will instead guide you to your destination.

This is the problem when trying to make a route out of a track inside the GPS.

That is why I suggested this morning, that you not just use the route (routes provide directions), But also display the track you have uploaded from Google Maps. The benefit of displaying the Track and the Route at the same time, is to provide you with your original designed route on your GPS display, even if it doesn't provide you with directions.

Tracks do not get recalculated. An imported Track does not change.

If the map data is different on the GPS than the map data that you used to create your original route/track, you may end up with a Track that is next to the actual road, but at least you will be able to adjust for that as your ride your route/track.

I believe the best thing would be to use a GPX converter, like GPS Visualizer to convert your Google Maps Routes to Garmin Version GPX files and then to import them into your GPS.

https://www.gpsvisualizer.com/

This is exactly what I am doing, creating the route in Google maps, saving as  KML, going to gpsvisualizer.com to convert to GPX.  I put the GPX file on the microSD card, insert the card into the Nav IV and my defined route shows in the Tracks App.  I select the defined route in the Tracks App, select the button that looks like a wrench at the top left, and select "Convert to Trip".  When that is done, my defined route shows in the Trip Planner App, from which I then select my defined route.

 

 

Thanks Bernie, I appreciate all of your patient guidance.

[Colorado Jeff]

19 hours ago, Bill Murray said:

Jeff, there is also an excellent series of YouTube videos by Don Norwood that teach you how to use Basecamp. The video series is private, so you cannot discover it without a link to it. I found the series through a discussion on the BMW MOA forums a few years ago. Below is a link to a playlist of these videos. If the link does not work for you, let me know and I will publish the links to the individual videos in the series (34 in total).

 

https://youtube.com/playlist?list=PLAzqCfh_XhMat1SOOXwMYZ4i0MuV2Z0Io

 

 

Thank you Bill!  I will definitely take a look at those videos.

[Colorado Jeff]

6 hours ago, dirtrider said:

Morning Jeff 

 

You should really consider at least getting a little familiar with Base Camp, it has way more to offer than just making or transferring a route into your GPS device. 

 

For the most part it is not difficult to use once you understand the basics. 

 

On a problem like you are having now Base Camp has a playback option, that allows Base Camp to preview ride your route right on your computer screen.  It has a speed option from real time to x1000 (x100 makes longish routes go through fast but just slow enough so you can see if it is tracking correctly) 

 

You can just hook your GPS to your computer, import the route from your GPS into Base Camp then open the route, & pre-ride it on the computer screen. 

 

It helps to also have (or import) the track that you started with as you can overlay the imported route (from the GPS) over the original track to verify that they match EXACTLY,  then as you preview ride the imported route you can watch it follow the track to see if it does in fact follow the original track or deviate from it. You can then zoom WAY in to find &  understand  what went wrong & why it happened. 

 

Not 100% guaranteed to catch every problem but pretty useful at catching most. 

Added: I would also like to see how your Nav 6 converts a track to a route, most Garmin device conversions (including Base Camp) only give the conversion route a start & finish point (no intermediate via points). If the route is logical & straight forward then it can work with just a start & finish point, BUT, if ANYTHING goes  wrong (like missed turn, road isn't exactly matching the map data, small glitch, etc) the GPS will try to route you to the next via point best it can but with just 2 points on the converted route & the only one in the direction of travel that is the end of route point so the GPS won't usually put you back on YOUR route but just route you to the end point as the GPS thinks it should.  

 

 

Thank you dirtrider, appreciate your views.

[Bill_Walker]

I'm late to the party, just read this, but I think there a couple of basic GPS concepts that you're unaware of, Jeff.

 

1) Waypoints: a waypoint (sometimes dumbed down as "saved places" or some such) is just a saved location.  Waypoints can be used as destinations, but they can also be used as intermediate points in a route (aka "trip"), in order to force the route onto certain roads (or just to stop en route at that great restaurant whose location you saved).

 

2) Map Datum.  This is how a set of maps is defined, and maps from different sources, or different years, will be subtly different.  Thus, if you calculate a route on Google Maps and then import it to your GPS (which uses Garmin's maps), it is likely that at some point your GPS will see one of the points on the route as not actually being on a road.  Think of it like holding your finger on a point on a paper map, but then somebody tugs the map just slightly while your finger stays in the same place.  Now your finger's not pointing where you thought it was.

3) If the GPS thinks you're not actually on a road, or that you're on a different road, then it believes you have gone off your selected route, and if auto-recalculation is enabled, it will now recalculate the route to the next waypoint on your route.  With your imported routes, the next waypoint is the final destination, so you get a whole new route, not an alteration of your existing route.  With BaseCamp, you can insert waypoints on the roads you want to travel to force the GPS to navigate there, even if you go off route along the way.