PacePro Plan not working when following a course

Ok, I think I figured it out:

A PacePro Plan that is tied to a course ONLY works if you start your workout at the starting point of that course. I just created a new course that starts at my front door, and when "running" it (simply pressing Go as I did before) it happily gave the distance, my overal ahead/behind time, split pace,.. etc.

Which now begs the question: What is the accuracy threshold for this? If an organizer provides a GPX file to a race, but the start point is not pinpoint accurate, will the PacePro Plan still work? Can I be off by 10m, 100m, 200m,...? It would be great of someone from Garmin could give some insights in this.

Remember that PacePro compares your effort against course you have drawn on map vs your actual "path"

I mean even you have perfectly aligned Course on map, in the real life you will be running several meters more than that.

I have never managed to follow painted stripes on the road.

This mean by definition your PacePro plan HAS to be offset somehow.

You should not be worry about that at all. It is just "reminder". Progress indicator. 

For me during my last Half it was just announcement: from now on just have fun from running. You are way behind schedule and your Plan A is in the bin.

Be as it may, I would still like to know how much drift there is from the start.

I also noticed something else: If you load in a PacePro plan, and then let the watch sit idle for about 5-10 minutes before actually pressing start, PacePro does not work either.

It's like loading in the plan immediately sets your start location, but if you then actually press the GO button it will already be off. For example, when I did the test yest now it immediately told me my new pace for kilometer 2. Like it had already drifter a kilometer from the actual start just by sitting here, completely messing up the plan.

I would actually consider this a bug.

I have tried to say, that it might be difficult for you to draw Course starting "exactly" in the place where it starts. You know what I mean. Next thing is how that location will match the moment you press Run button on the watch.

I have another problem with PacePro and Course.

My last running Half Marathon started on the bridge. 

As you can see Course elevation is not on the bridge but on the water. 

You can imagine what PacePro plan looks at the begin, but luckily you can Edit Splits manually and correct this.

How I have started this race? Created Course and PacePro in advance as you did.

At the starting point few minutes before crossing start line, selected Run. Then before pressing Run, I was waiting to get GPS and connected External HRM. Then enter to Workout menu (Up button) and select Navigation. Then Courses select that one, and then Run button to seect PacePro. Not just Do Course. Only then watch is asking to if I want to Use Plan, plus asking if I want to Enable course navigation. 

After that process you can wait several minutes (I guess up to 30) before you will cross start line and Press Run to activate whole process.

It worked for me. Should be the same good for you.

You can test this yourself. From your past activity, save your known track as Course. Create PacePro plan. Then when you will be at your "starting" position step back several meters (I would suggest something like 100 m) to start your Run. 

You should see if that works for you. 

Matthias, I have not used PacePro since the latest update, but have actually been impressed by how it is handled by the watch. 

The first course I used it for started/ended indoors, so I knew the watch would not be able to find a GPS signal until I was outside and would not capture the end correctly, but overall that was probably about 200m worth of a 25K race. 

I mapped the course from the edge of the building, through town and returning for the finish across bridges and hills.  The course had an unexpected change in route due to road construction that had started earlier than anticipated; while I was "off course" the watch was confused and pacing not accurate, but within a few feet of returning to course, it found itself and resumed as expected.  I was ok with the pacing being off during the start/finish and the detour and still able to utilize it as expected to help me achieve my goals in that race.

The second race I used it for a few weeks ago had a very imprecise map provided (showed roughly 22K for a 25K event).  Recognizing this, I extended various points along the course to get an accurate distance and was confident the finish was correctly placed.  I set the pacing for 25K and the watch struggled every time I missed an extension or the course went where it wasn't planned, but having the distance and finish point accurate assured my ahead/behind was trustworthy enough for me.  Precise to the 0:01 for each K?  No, but based on the course details given ahead of time and markers along the route, it was good enough for me to trust my finish within 0:15.