Garmin vs. Strava distance

My workout, which I was pleased with, is at the end.
But with Garmin being down due to a ransomware attack I got a chance to see what Strava would do with the same data points that Garmin connect uses.

This is the course in question. On Thursday, I did this course 3 times then a bit extra. The Garmin measured it as 6.3 miles and Strava got this at 6.4 with the same data points that the Garmin used.
Here is the Strava output, which includes the extra partial loop.

The time before, Garmin measured these two loops as follows:

Strava gave me 4.3 on the same data:

Now look at today’s walk, where the Garmin and Strava got the same mileage with the same data points:

6.22 (which is what the Garmin showed).

So, why the difference?

(yes, this is based on only a few outputs)

First note that there was a time when the outputs were all but identical. That tells me it is NOT “round off” error (e. g. one program carrying more digits than another).

But note when I had a different number: the lines are all “wiggly.” Reason: the two that were different were weekday morning walks; there was much more traffic. I made course corrections to avoid other runners, pedestrians and vehicles on the road.

Today’s trek was on a less crowded day: note the lack of “wiggles” in my path.

My inference: the difference is in how the algorithm connects the dots. First of all, each “dot” is really just an intersection of lines from different satellite signals and those lines of intersection form a polygon rather than an exact point.

The centers of these “polygons” formed by the signal lines determine your position points. So, what to do with these position points?

The crudest way is to draw a straight line path between these points (black). One can select the points in batches and fit different sorts of curves by either a spline or by a least squares principle.

Here, I approximated paths by cubic splines between each group of 3 points and one that uses all 5 points (but doesn’t quite cut through all of them.)

But one gets different distances when one uses a different “curve fitting” algorithm, and it is my guess that Strava algorithm fits curves through more of the points than the Garmin algorithm. And the difference is less when the curve has less “wiggle” to it (in math terms: smaller magnitudes for the second derivative).

Anyway, that is my guess.

My workout: I warmed up my glutes and back..(15 minutes)

Deadlifts (low handles, trap bar): 10 x 134, 10 x 184, 5 x 228, 3 x 250, 5 x 233 NO BOUNCED REPS. Note: this might not seem like much but at this time last year, I couldn’t get 225 for a single rep.
Then the walk:

It was 81 F at the start, 84 F at the end, 69 percent humidity. That is warm for us.

No glute pain. Not much knee pain either.


I got started way too late.
run: 4/13 miles in 51:38 (26:10 out, 25:28 back) was hot. Then 2 more miles walking; glute was singing to me ..should have stretched after the walk. Run was painless, though I was too damned stiff.

I need to be more disciplined in the morning; it helps to have an appointment.

And yes, there IS stuff I can be doing.

Another week gone

I start some training next week…should be interesting. I am putting the finishing touches on one project as well.

I still worked out:

2 mile jog (about 12-12:30 mpm)
pull ups: 5 sets of 10, 2 of 5 (chin ups)
bench press: hips down..more strict than usual: 10 x 132, 3 sets of 5 x 171
seated military (watch the chair): 3 sets of 10 x 44 dumbbells
rows: 3 sets of 8 x 132 trap bar
plank: 2:30

Also: a lot of prep glue is getting better.

Yes, I waste too much time on the internet; that might change next week. No, COVID is not going away just yet…sigh..

Downswing again?

Yesterday: 5.25 mile walk in 1:21:50 (15:36 pace) and it was painful at the end; didn’t stretch enough. I might try something more gentle before this morning’s weight workout. I am feeling a bit “out of sorts”; aches, pains, etc, but we’ll see how it goes.

In terms of social stuff: our country is so polarized and, well, even human decency is becoming a partisan issue. Here is how “they” are “owning us”: (and yes, these are grown adult men, not immature kids)

On a happier note: B and I maintained social distance and then “saw the athletes off” as they walked in a BLM demonstration:


Anxious times for many reasons…

Social Saturday

Illinois is in Phase 3 of reopening so I took advantage to visit Tracy for a short while; we maintained social distance and she has been strict in her shelter in place.
That added .82 miles of walking each way..not that I am keeping track. My Prius ran out of battery juice as I neglected to keep it going. I’ll call for a jump on Monday.

But I got a workout prior to that; deadlifts followed by a 7 mile walk at about 16:50 mpm (easy pace, easy effort; sort of warm)

Deadlifts before: 10 x 134, 10 x 184, 10 x 217, 10 x 184 (deficit for the final working set); quite a bit of glute warm up.
The walk: 1:59 for my 7.04 mile course. Walk was pain free.

About my weights and sports in general: Yeah, I played that game; maybe making this change or that change in my technique might help. And maybe it did…a few seconds here, a couple of pounds there. But ultimately, I suck because...I am slow and weak. That is all it really is. Sure, technique can help with injury prevention and maybe help a little. But only a little.


I did feel some pain walking to Tracy’s as I didn’t warm up before.

Her cats (3 of them) greeted me.


This is from the point of view of a Black Naval Academy graduate. A little bit of this resonates with me and it sounds very similar to what Black colleagues have told me.

Beating Trump: The Lincoln Project is run by Republicans who know how to win. We should listen to them.

Republicans are better at this than we are.

A little bit calmer

First: glue exercises
only weights this morning; I was a bit stiffer than normal.
rotator cuff
pull ups: 3 sets of 10, 5-5 (wide, regular), 10, then 5-5 (chins last set)
indoors: bench: 10 x 132, 10 x 154, 10 x 154
rows: 3 sets of 8 x 134 trap)
hip hikes
seated, supported shoulder (3 sets of 10 x 44)
deficit trap dead: 10 x 134, 2 sets of 10 x 184; second set of 10 wasn’t bad.
Workout took about 80 minutes; some troubling residual pain last night in my right knee…not terrible. Glute: coming along nicely; those band exercises appear to be helping.

I found an old race program; Azalea Trail 10K in Mobile, Al, March 5, 1982. I got Bill Rodgers’ autograph. Then I went to see Chariots of Fire that night in the theater; almost all young skinny guys in race t-shirts; I may have been the slowest one there.

Though it was my best ever, it was slow by the standards of the day and for a 22 year old.