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| Google maps distance query (Read 333 times) |
| view log |
posted: 1/8/2008 at 10:23 PM |
Hi all
This may be a really stupid question so sorry if so. I was just wondering with the Google maps feature where you can plot the run, does that measure distance as the crow flies so to speak ie as if the land was totally flat? Because if it was hilly terrain the run would be longer wouldn't it? Does any one else encounter this as a problem or feel that the pace or distance is not totally accurate?
Many thanks
Hank |
2008 aims:
30 March 14.1km fun run in 1:10:30 Actual: 1:06:54
One half marathon in <1:39:59
Gold Coast marathonJuly 6 2008 in 3:29:59 (ambitious)
Maintain 3-4 runs a week - even in winter
Run 2,000km in 2008 (significant increase)
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brian :) |
posted: 1/8/2008 at 10:37 PM
modified: 1/8/2008 at 10:37 PM |
Hi Hank,
The course distance is determined assuming a perfectly smooth and spherical Earth. You can get an idea for how hilly a course is by using the elevation chart (the  icon) it will even tell you the total vertical distance traveled.
Any hills or the general elliptical shape of the earth will throw off the distance measurement. I don't recall the exact margin of error, but it shouldn't create a noticeable difference unless you're going hundreds of miles over mountainous terrain. 
-brian |
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| view log Funky Monkey |
posted: 1/8/2008 at 10:43 PM
modified: 1/8/2008 at 11:03 PM |
No, it does not really make much difference to include this in the distance calculations.
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Doing the math:
Grade is defined as rise over run, multiplied by 100. So a course that rises 100 feet over a mile is (100 / 5280) * 100 = 1.8%
To determine the distance run on the hypotenuse of this route, you can apply the Pythagorean Theorum, which states that A^2 + B^2 = C^2 (where the notation ^2 means squared). So in a triangle formed on one side by the distance 5280 feet and on another side by the distance 100 feet, your hypotenuese = sqrt(5280^2 + 100^2) = 5 280.9. Catch that? A 2% grade, which is just over a 100 foot climb over a mile adds one foot to your distance. That is less than 0.1% error per mile, which is insignificant. That is less than a foot of error per mile.
This may matter more on a nasty run, such as the Pikes Peak Marathon. The Pikes Peak Marathon includes a 13 mile climb up more than 7500 feet, with an average 11% grade. Assuming you actually do climb 13 miles in 7500 feet, let's determine the error. 13 * 5280 = 68 640 feet. Applying the Pythagorean Theorum, we get sqrt(68 640^2 + 7500^2) = 69 048.5 feet. That is a difference of 408.5 feet over 13 miles (31 feet per mile), or a 0.6% error.
Or for a steady 10% grade over a mile:
A = 5280 feet
B = 0.1 * A = 528 feet
C = sqrt((5280^2) + (528^2)) = 5306 feet
So, by climbing a 10% grade for a whole horizontal gmap mile, you have added 26 feet. That is an additional 0.4%. Not worth it to me.
I think that with these mapping tools, you are more likely to introduce more feet to your expected distance run by your mapping (im)precision rather than by the effects of elevation change.
MTA: and most of your runs are 1-5% grade at most, and that only inconsistently as it rolls up and down. Those are likely to have <0.1% error. |
| It's all fun and games until the flying monkeys attack. |
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| view log |
posted: 1/8/2008 at 11:54 PM |
Wow, Trent, are you sure you're not an engineer? Thanks for the calculations! This is my favorite website in the entire world. Running plus math!
Teresa |
| Maine Coast HM, September 21 |
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| view log Funky Monkey |
posted: 1/9/2008 at 1:04 AM |
| Ha. Naw, I'm just a geek. |
| It's all fun and games until the flying monkeys attack. |
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| view log |
posted: 1/9/2008 at 1:52 AM |
damn, guess i'll just have to keep running to get faster and stop trying to find other ways!! 
Thanks for the info though
Hank |
2008 aims:
30 March 14.1km fun run in 1:10:30 Actual: 1:06:54
One half marathon in <1:39:59
Gold Coast marathonJuly 6 2008 in 3:29:59 (ambitious)
Maintain 3-4 runs a week - even in winter
Run 2,000km in 2008 (significant increase)
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| view log got gams? |
posted: 1/9/2008 at 2:10 AM |
| Quote from Trent on 1/8/2008 at 10:43 PM: No, it does not really make much difference to include this in the distance calculations.
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Doing the math:
Edited while I finish off a 3 liter box of wine. |
Kirsten . . . --> GIRLS GIRLS GIRLS <--
• Ladies Locker Room •
.: 2008 Goals :.
• Run 1500 miles
• October 5 - 1st marathon - Milwaukee Lakefront - in my home state of WI
• PRs: 5k ~ 15k ~ 25k |
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