New unit

Any chance of integration with Di2 for the top shifter buttons and gear position?

I understand the 130 won't display things like TSS, NP, or L/R balance from power meters, but are those data elements saved for post-ride analysis?

Navigational times are only provided when following a course or when using the back to start along same route function.

Turn instructions and turn warnings require there to be course points in the course file. The inclusion of course points for turn instruction is a function of the site you use to build the course. You do not need to add pre-course point course point. The Edge will notify you as get close to the course point and then again as you reach the course point.

So you confirm that while there is no base map underneath, the 130 will calculate the kms/mileage along the bread crumb accurately?

What happens when you move off the bread crumb/course points - what will 'Distance to Destination' read then?

So you confirm that while there is no base map underneath, the 130 will calculate the kms/mileage along the bread crumb accurately?

No map is needed. (None of the units use a map for this.)

All the necessary data is in the track.

That data includes the coordinates but also, for each point, the time (related to speed and the "virtual partner"), the elevation (optionally), and the cumulative distance.

Originally, the tracks used by the units were recorded rides. The programs (like Garmin Connect) that create a track are basically creating a fake ride.

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As you ride, the device follows along the track (by keeping track of the track point you are closest to). The device doesn't backtrack. That is, it only moves forward along the track.

The course points are a separate set of points. They have the same data as the track points but also have a short bit of text (like part of a street name) and an icon (like an arrow).

The units know the next course point and the last point in the track.

The units determine the distance to next and destination by subtracting the cumulative distance associated with the track point you are currently nearest to from the cumulative distance of the next course point and the last track point.

What happens when you move off the bread crumb/course points - what will 'Distance to Destination' read then?

If you move too far from the track, it appears the units stop following along the track. That means that the distance to next/destination is based on the track point it stopped following at.

The units are expecting you are following the track (which means they don't do anything complicated when you go off course).

When you get close to the track, the units resume following the track at the nearest track point. (This lets the unit handle you skipping part of the track.)

Since the distance to next/destination uses the cumulative distance associated with the track point, the extra distance you might have traveled off course doesn't matter.

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It's set up so that the units only have to keep track of a few things.

1- your current location.
2- the nearest track point (the position in the track your current location most-closely matches).
3- the next course point (used for the next turn instruction and "distance to next").
4- the last point in the track (used for "distance to destination").

Because each point the unit is keeping track of already has the cumulative distance along the track, it's easy to calculate the remaining distance (the distance to next/destination). The remaining distance (since it's based on data in the track points in the track) isn't affected by the actual distance you traveled earlier (or whether you followed the track).

1) distance to next/destination is only accurate when am riding along the breadcrumbs

2) when one strays away from the breadcrumb the distance to next/destination will freeze until one returns to the breadcrumbs

1- yes.
2- yes.

The device could provide some sort of estimate (like the straight line distance) but none of these possible estimates has a good chance of being accurate because the unit has no idea what path you are going to take.

As there will be no base maps - will there be street information in the turn warnings? what kind of turn warnings are there?

That's what the course points are. These are a feature of TCX (or fit) files.

These are location marked with 10 letters of text and an icon. The 10 letters are usually a street name (the first 10 letters) and an icon representing the direction to take (like a right or left arrow). There's a screen page that shows them as a list but each one will pop-up on the screen as you get close to it. The older units showed them at the turns; the newer units show them before the turns (which is more useful). There's are a few other types that can be used to indicate other things like food stops.

How well they work depends on how closely the map used to plan the track matches the real world and how closely you follow the track.

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Garmin doesn't change how a feature works (except in small ways). That means the 130 works like other units (for the same feature).

I understand the 130 won't display things like TSS, NP, or L/R balance from power meters, but are those data elements saved for post-ride analysis?

Same question here - is Cycling Dynamic data recorded in the fit file but just not shown on screen, or both not shown and not recorded?

Not shown or recorded. It has basic power data support.