Saturday, September 3, 2011

Diablo North Gate: two Strava segments

Today, encouraged by the temperatures in the 70F's being reported for the Diablo summit, in striking contrast to the bone-chilling fog of San Francisco, I put on a jacket and rode to BART. I heard the announcement for the Pittsburgh-Bay Point train I wanted as I reached the top of the stairs, so I ran down the stairs in my cycling shoes and, after a few contact fouls with people leisurely walking the opposite way, got onto the train only 5 seconds before the door shut.

Ironically BART to Pleasant Hill takes about the same time as it would take me to ride out to the Golden Gate Bridge. Then the suburban-timed traffic lights from there to the base of the climb are no more delay than the riding the pedestrian path across the Golden Gate Bridge. Despite this for a long time East Bay rides were all too rare for me. Instead I bundled up against San Francisco and Marin's summer chill and rode north. But I've been riding Diablo more recently, trying to work on my extended climbing, breaking out of the rut of efforts 5 minutes and less. Even Mt Tamalpais lacks continuity from the most popular access point in Fairfax: that climb is in segments separated by short descents. For a continuous effort, Diablo is the easiest weekend access, the climbs on the peninsula south of San Francisco less attractive due to Caltrain's poor weekend service.

So in part to help kick myself out of my post-half-marathon tired legs slump, today I rode Diablo.

The Low-Key Hillclimbs last climbed Diablo in 2009. We started the climb just past the gate which sits on the road at the northern boundary of the park. This is also where C4 Racing starts their race, which goes 10 km up the hill, ending 500 meters from the junction between the North Gate, South Gate, and Summit Roads. So I think it's safe to say this is a popular "start" to the climb.

For the finish of the climb there's no question: the end of Diablo is a memorable experience. Strava has it at 15.2% for 200 meters. And at the end of 1100 vertical meters you feel every % of that... But it's the final sprint, so you do what it takes to make it to the parking lot at the top. A sign tells you where you are:

Brenda Brunner photo

So remembering my climb of Old La Honda a week and a half ago, I made sure to use the lap timer on my Edge 500. I'd upgraded my firmware so the Strava representation of my lap should be within 2 seconds or so of reality.

Here's the start of the lap as reported by Strava:

start of lap

The sign is near that big tree, so the position here is fairly close to where I hit the lap start.

Then here's the finish:

start of lap

There's a bit more error here; obviously I wasn't riding off the side of the road. I hit the lap finish close to where the paint is directing traffic, somewhat past the end of the indicated segment. But the error here is also fairly small.

So I was surprised when I compared my lap time to what Strava gave me for the segment Diablo NG to summit.

Here's what fitdump says about my lap:
temperature (13-1-SINT8): 37deg.C (37)
timestamp (253-1-UINT32): 2011-09-03T12:59:34 (684014374)
start_time (2-1-UINT32): 2011-09-03T12:01:12 (684010872)
start_position_lat (3-1-SINT32): 37.9017256deg (452185200)
start_position_long (4-1-SINT32): -121.9931266deg (-1455434692)
end_position_lat (5-1-SINT32): 37.8815485deg (451944477)
end_position_long (6-1-SINT32): -121.9149209deg (-1454501662)
total_elapsed_time (7-1-UINT32): 3501.660s (3501660)
total_timer_time (8-1-UINT32): 3501.660s (3501660)
total_distance (9-1-UINT32): 17607.62m (1760762)

Time was 58:21.7. This is only 0.7 seconds longer than Strava claimed for the lap, a smaller difference than I'd seen at Old La Honda due to my firmware upgrade and selection of one-second sampling.

But when I look at the segment, it says 58:35. So where'd that 14 seconds come from?

The listed start for the segment is the same, so no difference there:

start of segment

But the finish is quite striking -- the finish was marked in the middle of the parking lot:

end of segment

Bad match, perhaps? Here's the reference data:

end of segment reference data

Also the middle of the lot.

That's sort of strange, since many riders will reach the lot then stop, or even reach it then take a tight left to descend. On the plus side, moving the end of the segment away from the steep section guarantees riders will have completed the entire steep portion. But in this case it seems almost criminal to destroy people's results because they stopped in what at least in theory could be a congested lot.

So there's another segment: "Diablo North Gate to Summit". I'll not post images like I did from the last one, but if you follow the link you can see this one starts considerably later. South of the north gate itself, there's a bit of a rolling section which includes a descent before the road begins its monotonic ascent. This segment omits this beginning portion, which I understand. But the finish of this segment is what's most unfortunate. It's at the beginning of the 15% grade leading to the lot! I'm sorry, if you reach this section then faced with the sheer horror of what awaits, you turn back, then you, my friend, have not climbed Diablo. You've got to include that last portion.

So two segments, neither really doing the job. Of course I could define my own, but there's already too many segments flying around. Just remember when you climb Diablo to keep going once you reach the lot to make sure you trigger that first, more complete segment.


djconnel said...

I couldn't resist... using Kevin Metcalf's nicely truncated data from his winning ride at the 2009 Low-Key Hillclimb (week 7), I created a new segment for the climb. This goes from the entrance sign to the leading edge of the parking lot.

If Low-Key returns to Diablo it will likely be on a self-timed or Strava-timed basis, since they are unfriendly to "events" there which potentially delay car traffic in any way.

Anonymous said...

Ouch. Bad segments on a major, well-trafficked climb. Nothing wrong with creating yet another one in this situation, and kudos for finding a good set of ride data to base the segment on.

Which one is the segment you created? Your link just points to your whole ride, not the individual segment.

djconnel said...
This comment has been removed by the author.
djconnel said...

Thanks for the comment! I messed up -- I'd intended to post a link to the segment, not the ride. Here's the segment:

Timing was one second off from my lap time, so it should be fairly good.

3 of the top 8 times are from that 14 Nov 2009 Low-Key Hillclimb. Interesting how even a friendly competition brings out the best in people.

I wonder what would happen if we declared a "ride it when you want during this weekend" call for times. Would that be considered "an event"? Not by the park service definition.