Why is VP (Virtual Partner) reappearing even if it should be miles ahead or behind on a course?

Tisztul_A_Visztula said:

a) Is it, because in case of a sequence of "off course" and "course found" there is a recalculation of VP postiion, and NOT from the beginning of the course, but from the location one reverts to the course?

Yes, maybe 5 years ago ? Garmin modified the behaviour of the VP so it could be made to "snap to your location" (never understood why?) but in the coding to accomplish this they also (by design or "accident") made the "snap to" happen if the GPS signal was lost (ie in a tunnel or other heavy cover). IMHO this made the VP even more useless and annoying an removed the only use case for a VP. Thus even though you set the VP speed high or low it will often miss your company and snap to your location! My other theory is that this behaviour is to remind us that the VP symbol is twice the size of the often almost invisible smaller user location symbol / cursor and Garmin just wants us to remember what Garmin thinks about its customers?

I know that case "a)" is absolutely true.  If you stray off course and come back, your VP starts with you from the same location you rejoin the course.  I see this regularly on an out-and-back run I do on a rail trail.  If I turn around early, VP rejoins me even though he was ahead of me.  I just ignore it.

Yesterday I made some more tests  and it seems that  although VP speed can be as high as 7 digits in km/h, if you keep it  under 1000 km/h then there is a much higher chance that your course is properly sent to and processed  by your Edge.

I mean if the speed  was  like 99999 km/h or 999999  km/h then sending the very same koop course of 170 km  from GC resulted in a fully simplified two-point course (start and end being  very close to each other). If the speed was lower like 9999 km/h then the course still missed  so many  points that it was a sort of polygon without  real “curves” / “arches”. When  I applied 999 km/h the course was more or less perfect. 

A) The result of this test was that  VP time was around 8-9 minutes, so if you do not leave your course for 8-9 minutes and dont lose GPS signal  (btw thx for the additional info, too) you get rid of VP, because I suppose that a VP which has already finiished never appears on the map again, does it?

B) A sidenote is that even if a VP speed is so low that a loop course seems to be properly processed by Edge I can see that  it tends to lose the few first points after the start point and the few last points before the end point. But not always and I have no real bet why?

i)  map issue around my house which is the start point?

ii) even a relatively modest, but not reasonable VP speed has an effect on the course importing and/or drawing? (You know I mean if a segment is too short for VP and its VP time is less than 1 second then Edge drops the end point of that segment to get a longer one being at least 1 sec?

I will say that "A)" is true, once VP is finished I've never seen it reappear.  I think this strategy is the best if you wish to dismiss VP for the ride.

Yep, I also tried to apply 1 km/h to avoid the “VP is finished” message, too,  but the price for it the above mentioned returns in case of leaving courses.

Anyway I will stick to a high enough speed to get “VP is finished” message as early as I can without ruining  my courses.

Anyway is it just me who experienced this VP speed related partial course destruction detailed in “B)”?

Please reply as fast as you can even at an unreasonably high speed :-), because I realized  that VP related threads are closed very fast in Edge 530/830 forums like this one: https://forums.garmin.com/sports-fitness/cycling/f/edge-530/405609/how-can-i-deactivate-the-virtual-partner. 

Tisztul_A_Visztula said:

ii) even a relatively modest, but not reasonable VP speed has an effect on the course importing and/or drawing? (You know I mean if a segment is too short for VP and its VP time is less than 1 second then Edge drops the end point of that segment to get a longer one being at least 1 sec?

I did more tests with VP speed and it seems to be the case. If the distance between the start point and the location of the first directional change of the course is so low that VP would cover is less than 1 second the point of the first directional change of the course is dropped and the algorithm goes on.

If the distance between the start point and the location of the second directional change of the course is so low that VP would cover is less than 1 second the point of the second directional change of the course is dropped, too. Etc.

Edge 530/830 needs a long enough first line in the course to be covered by more than 1 second by VP.

Amd the same is true for the end point.

It is the result why  sometimes a brutally high VP speed results in a simple line between start and points. And if you increases more the VP speed then no course is shown, between the VP time would be practically zero.

I observed that these high VP speeds go with miscalculation of VP times, I guess rounding is the sinner.