Strava noob

[lordofthemark]

So I got it to work this morning. Very pleased to see that some people have biked the segments I did slower than I did (though I think some of them were doing it as part of a much longer ride) Of course I was still near the bottom of all the lists. More importantly, the times were good for me. I also saw just how fast I was going on the “Shirlington descent” to inform future discussions of safety, and braking. And to see what the gradients are.

So, questions.
A. Since I did not declare my ride private, anyone can see how I did, and where I rode, right? But not when?
B. I saw a few familiar forum names. Is it impolite to follow someone on Strava without their permission? Is there a group I could follow/join instead?
C. Would it be considered presumptuous to create segments already? I want to create one for my entire usual commute, and one for the route from my home to Shirlington. And maybe for the return from Shirlington to my home via Walter Reed. (I know I need to do that on the website, not the App)
D. I thought I would get to see watts estimates, but that seems to be Premium only
E. What else do I need to learn about Strava before signing up for Freezing Saddles?

Topic

[AFHokie]

@vvill 101927 wrote:

I don’t know exactly how the wattage formula works but I’d imagine it doesn’t take variables into account other than speed/acceleration, gradient and weight.

If you overshoot a ride you can go back and trim off parts, at least on the website.

Another thing to keep in mind regarding wattage accuracy; Strava does not use the GPS signal to calculate elevation. I think they just use known topographic elevation data, but don’t know for sure. For example if you cross a river it will show you at the river elevation not the bridge elevation, so it will think you suddenly descended to the river and then back up on the other end. I’d guess that sudden descent and hill climb will throw off wattage.

Interestingly, I’ve found not all handheld GPS units use the GPS signal to calculate elevation either. I don’t know if all of them don’t but the couple I’ve owned instead use an internal barometer. I’m not sure why the don’t use the signal since as long as you ‘see’ four or more satellites you can calculate elevation. I was surprised when I fired mine up over the Atlantic once to see where we were and it gave me the cabin pressure altitude instead of our actual.

Additionally, I’m not sure how many are aware of Strava tracking errors, but they do occasionally occur. I contacted Strava about it and unfortunately, there is no way to go back and manually ‘clean up’ your route. On a longer ride this can significantly throw off your mileage. I have a ride that shows me taking a rather significant cross country detour through Rock Creek rather than riding on Beach Dr.

[mstone]

GPS elevation data is generally pretty bad on consumer units (much worse than latitude/longitude) and suffers from significant jitter. In general the barometric data will be better, especially on a unit that periodically recalibrates based on known data points.

[vvill]

@AFHokie 101936 wrote:

Another thing to keep in mind regarding wattage accuracy; Strava does not use the GPS signal to calculate elevation. I think they just use known topographic elevation data, but don’t know for sure. For example if you cross a river it will show you at the river elevation not the bridge elevation, so it will think you suddenly descended to the river and then back up on the other end. I’d guess that sudden descent and hill climb will throw off wattage.

They do use barometric altitude if you record using a device with an altimeter.

https://strava.zendesk.com/entries/20965883-Elevation-for-Your-Activity

[Steve O]

@mstone 101937 wrote:

GPS elevation data is generally pretty bad on consumer units (much worse than latitude/longitude) and suffers from significant jitter. In general the barometric data will be better, especially on a unit that periodically recalibrates based on known data points.

I almost always use the elevation correction feature. On the web site, click on the word “Elevation (?)” as shown here. Strava will then replace the elevation provided by your device with elevation from known maps. It does get things wrong sometimes on bridges and tunnels, but overall I think it is a lot more accurate than my Garmin.

[IMG]http://bikearlingtonforum.com/attachment.php?attachmentid=7190&stc=1[/IMG]

[Tim Kelley]

In my experience, the wattage numbers are not even close to being consistent with what a power meter says they are. Take all those leaderboard wattage estimates with a couple grains of salt unless they have the little lightening bolt symbol next to them.

[AFHokie]

@mstone 101937 wrote:

GPS elevation data is generally pretty bad on consumer units (much worse than latitude/longitude) and suffers from significant jitter. In general the barometric data will be better, especially on a unit that periodically recalibrates based on known data points.

I wondered how it re-calibrated since barometric pressure can change significantly in a short period of time.

[mstone]

@AFHokie 102071 wrote:

I wondered how it re-calibrated since barometric pressure can change significantly in a short period of time.

Even without periodic recalibration, the barometric reading is probably going to be more useful to determine cumulative elevation gain; even if the absolute reading is wrong, there’s less jitter. (The GPS data can make it look like you’re going up and down big rollers while you’re standing still.) But overall, yeah, any altitude numbers you get on a bike are mostly for gee-whiz factor rather than useful data.

[Orestes Munn]

Handheld GPS units have told me I was going up and down (small) hills when I was out on the Bay in a flat calm. I do have a good, fixed one, but it has the intelligence not to read out elevation.

[ian74]

@Steve O 101866 wrote:

You can join the BikeArlington and/or Bike DC groups. And there may be others I’m not aware of. In Freezing Saddles, you will be required to join the group that is your team.

People who do not want to be followed will change their permissions, so that you can only “Request to Follow.” Then they will need to approve you. If, like me, they do not have that, then you are welcome to follow if you like. I don’t consider that impolite. Just don’t be faster.

I just joined this group. Thanks for the information Steve O. For anyone else not in it, who wants to be in it, the link to the group is http://www.strava.com/clubs/8123

Hahaha, they just let anyone in too!!!!! EVEN ME!!!!

To quote Groucho “I don’t want to belong to any club that will accept people like me as a member”

[AFHokie]

@mstone 102077 wrote:

Even without periodic recalibration, the barometric reading is probably going to be more useful to determine cumulative elevation gain; even if the absolute reading is wrong, there’s less jitter. (The GPS data can make it look like you’re going up and down big rollers while you’re standing still.) But overall, yeah, any altitude numbers you get on a bike are mostly for gee-whiz factor rather than useful data.

I still tend to look at elevation from an aviation standpoint; a few feet off could mean the difference between living another day or a smoking hole…but you’re right, on a bike as long as it accurately records elevation change, who cares if its a few feet high/low from your actual.

[baiskeli]

@AFHokie 102128 wrote:

I still tend to look at elevation from an aviation standpoint; a few feet off could mean the difference between living another day or a smoking hole…

That can apply to bikes too.

[Author]

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