The online map calculates elevation gain in this way:

1. The course route is created by joining small line
segments together. At various intervals along the
segments, sample points are used to query elevation
data from the U.S. Geological Survey (i.e. satellite
data).

2. This elevation data are plotted on a graph to
create the elevation profile.

3. The net elevation is calculated by adding together
all the elevation gains between the sample points.

Thus, the net elevation gain is an estimate based on
the number of points used to create the route and the
accuracy of the available elevation data (which can be
skewed when going over a high bridge, for instance).

In practice, I have found it to be fairly accurate...
but it should not be used in a court of law, for
example.

hope this helps,
Jeff

--- Mike wrote:

>
>
> "I noticed the map's posted elevation gain is
> 1,338/lap. The BB flyer says 750/lap.
>
> Anyone know which is correct?"
>
> The website says 750' net elevation gain....
> Which includes the number of feet descended.
> It's not the same as the number of total feet
> climbed per lap.
> _______________________________________________
> OBRA mailing list
> obra@list.obra.org
> http://list.obra.org/mailman/listinfo/obra
> Unsubscribe: obra-unsubscribe@list.obra.org
>

____________________________________________________________________________________
Need Mail bonding?
Go to the Yahoo! Mail Q&A for great tips from Yahoo! Answers users.
http://answers.yahoo.com/dir/?link=list&sid=396546091