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Google Earth Measurements

peteriegelpeteriegelRCMBB Founder
I'm convinced that Google Earth can be a big help.

I just finished a 15 mile course that was supposed to be an unexceptional, if pleasant, out-back on a nice, straight, level rails-to-trails. Unfortunately, my first measurement went all the way to the end of the available pavement and came up 2 km short, 1 km each way. It was possible to scramble down a steep gravel bank and reach a road that had enough room for the extra, but that was not really an option.

I used Google Earth to measure several options. Fortunately, the area in question had high-resolution pictures. I was able to see the lightpole at the start, and the adjacent one. I plotted an extra out-back at the start, between the two poles, and Google yielded 1077.5 meters. From past experience I trusted it. I’ve learned that I can do this. If you blow it up you can see the curbs quite nicely.

Yesterday my two measurements of the distance yielded 1075.73 and 1075.57. I was pleased, as when I got to the top end I reached the TA 64 meters before the pavement ended.

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J jamesmMember
I agree, it is a good tool for laying out the race before starting to measure. Google earth and MS "Streets & Trips" are good tools to get the lay of the land.

I have worked out possible courses on the systems, then faxed them to the RD, prior to meeting on the site to figure out what is doable.

Streets and Trips has the advantage that you can run it on a laptop in the field, without an internet connection. The disadvantage is it is only a vector based system and only shows streets. It does not have the bit map photo detail that google earth can provide.

Both systems help to give a first cut that sanity checks the RD's often wild ideas.

The ability to try out different routs, this side of the block v that side of the block, taking the first or second left, and finding the approximate difference in length, from the comfort of your computer, that can't be beat.
peteriegelpeteriegelRCMBB Founder
Using Google Earth for Measurement

Your computer must be able to use Google Earth. If the computer can use it, you must figure out what to do by playing with the program.

The area where you are measuring must be photographed in high definition. Columbus, Ohio, where I live and measure, is photographed in high detail. Beirut, Lebanon, is photographed in somewhat less detail. If you do not have the detail, it is hard to use Google Earth to measure.

When you measure using Google Earth you will get a good estimate of length, but it will not be good enough to meet world standards, which use the calibrated bicycle.

Some streets are invisible because of the shadows of tall buildings. Google Earth can be a help, but not 100 percent of the time.

Perhaps others will provide more information
peteriegelpeteriegelRCMBB Founder


A puzzler:

An alternate route is proposed. See above.

When I look at this partial map of TX05092ETM it looks to me like the existing and proposed routes between mile 1 and mile 2 are virtually identical. The existing route is a tad shorter because of the diagonal on Congress St, but not much.

I would expect both routes to measure within a meter or two over the mile 1 to mile 2 interval. Whoops! The proposed route crosses Congress St directly, but the original route does it on the diagonal. The width of Congress St will be part of the difference.

I checked using Google earth, going between the east curbline of Leeland/San Jacinto and the south curbline of LaBranch/Commerce.

I got a disagreement.

Will somebody check and let me know what you get. I'm quite puzzled.

The course is in downtown Houston
Last edited by peteriegel
AdminAdminMember
Pete,

I simplified things a bit by measuring both courses from the northeast corner of Leeland and Austin to the northeast corner of Congress and La Branch. I get a difference of 32 meters. Cutting the diagonals essentially eliminates the width of the streets, Austin(10m) and Congress(14m). The other 8m may come from changing sidewalk widths or the streets not being on a perfect grid perhaps. From a calculation using lat./long. points, I found that the angle I get at the corner of Leeland and La Branch when following the long path is not 90 degrees.

Is 32m close to what you got?
peteriegelpeteriegelRCMBB Founder
Mark - I got 33.6 using Google, with the proposed route being the longer. A bike measurement got 29. I would expected something on the order of 13 to 15, given that Congress St is ~15 m wide.

I had not considered that the width of Austin was also involved. That cuts the difference down even more. making the difference between bike and Google unremarkable.

Pavement is essentially the same on both routes.

Thanks for the confirmation.
jaywightjaywightCertifier
Pythagoras did pretty good work.

If you figure 16 blocks to the mile, so 100 meters per block, and a 12 meter wide street, the distance diagonally cross the street over the block is 100.71 meters, so the width of the street essentially goes away. The longer the block, the less impact the width of the street has- and the better the argument for simply measuring it along one side of the street and not risking your neck trying to ride the diagonal.

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