Mapmyrun.com Question (Read 1707 times)

Anyone know if that web site's mapping function compensates for the difference in ground altitude above the geoid (for all intents and purposes of this thread, the geoid can be synonymous with mean sea level)? If not, the distances reported will drift and become more inaccurate as elevation increases. The help section of the site talks about ascent and descent profile plotting but it doesn't mention where/how they get their data. I guess I could always just drive the routes in my car and compare the mapmyrun result.

Were you aware runningahead has a map program and that mapmyrun.com has a forum ? Before some one gets on your case, I still use mapmyrun when I run without a GPS.

Like Globule said. The error introduced by elevation change is insubstantial, especially when compared with the error introduced by plotting variability. It will be far less than 1% except on courses like the Pikes Peak Marathon, which has an average 11% grade over 26 miles. Do note that car odometer miles will have even greater variability than that introduced by the error from elevation change. Search function will reveal multiple mathematical proofs for this that have been posted over the years.

Mapmyrun usually ends up underestimating the distance because they don't take into account uphills and downhills in your run(their map is 2 dimensional.) Driving usually overestimates the distance because you can take a more direct route while running, while in a car you have to turn wide and follow the road exactly. My solution: average the two.

No, this is not why MMR or RA underestimate elevation change, and, as above, the distance estimate is pretty good. There are multiple ways to get elevation: Here is how the GPS measures. When running, the GPS device triangulates its position from satellites. The position it determines is supposed to be accurate to within 1-2 meters, but we all know that is hogwash in the hills and among trees. But usually it gets a trend from point to point, so while a single point may be off, the trend of several points are usually correct (e.g., they draw a line parallel to the road 20 feet north of the road). The GPS device records a point every 1-5 seconds. The point it records includes these data, derived from triangulation: Lat, Long, Elevation, Time. These Elevation data are fairly innacurate relative to the Lat and Long. To determine elevation, it simply adds all the change between Elevation points. This tends to overestimate elevation change substantially. Motionbased.com applies a correction when you upload the data. Motionbased essentially removes the elevation data from the points and replaces it with reference data from the USGS. The reference data is far more accurate than the data derived from triangulation. Again, elevation change is calculated as the total difference between points. RunningAHEAD.com and MapMyRun.com calculate elevation change by looking at points only every 1/10 mile (~ every 45-60 seconds) and comparing them to reference USGS data. This tends to underestimate elevation change if the course rolls a lot since there can be big up/downs in a 1/10 mile. When I run a local hill that starts at around 670 feet elevation and peaks at about 870 feet elevation (this course, the hill at mile 3), there is 200 feet of net gain, but there are numerous small rolls that do not show up on my RunningAHEAD.com map, do show up on Motionbased.com (also google/USGS based) that says the total climb is about 250 feet. My legs feel like 30000 feet of climb, but that is besides the point. So, what is the truth? Should every 20 foot climb is added in the elevation calculations? Well, that is more a philosophical question than a scientific one. My legs say yes.

Were you aware runningahead has a map program and that mapmyrun.com has a forum ? Before some one gets on your case, I still use mapmyrun when I run without a GPS.

I was aware, yes. It seems to use the same map as mapmyrun.com, but without the ads. All the answers in this thread are great, but my question was about total average elevation above mean sea level rather than elevation profile variability during a single run. For example, if the runningahead or mapmyrun maps do not take into account the local average terrain elevation above mean sea level then there will be significant error between 2, 1 mile points plotted at say, Chicago, vs. New Orleans. This is what my original question was about. I still haven’t had time to drive any of my running courses in my car yet.

Are all the threads in here making no sense at all today or am I have acid flashbacks again? Is the Chicago marathon shorter or longer than one in New Orleans? Does New Orleans have a marathon? Do they serve gumbo and crawdads? I'm going to try one more thread, and it better make sense. Or I'm going back to sniffing glue.

I use Firefox. I have adblock on. I still see ads. What features here are missing? And regardless, I am still not sure I understand how the length of a mile varies with elevation above sea level.

For example, if the runningahead or mapmyrun maps do not take into account the local average terrain elevation above mean sea level then there will be significant error between 2, 1 mile points plotted at say, Chicago, vs. New Orleans. This is what my original question was about.

This makes zero sense. Are you suggesting that because Chicago is higher above sea level (and thus, closer to the satellite taking the picture ) than New Orleans, the scales on the maps are wrong (parallax effect). If if were true, (and I don't' think it is because the street maps are based in statute, surveyed distances), the difference would surely be negligible.