In the latter case, you can help fix things by reporting the problem on the Trailmap Forum
|•||If unfamiliar with a trail's intersections, use a TRAILHEAD (i.e. North/South/East/West end) for the Start or Finish intersection.|
|•||For metrics for reverse of displayed route, simply reverse the elevation UP/DN gain/loss numbers.|
|•||For a loop round-trip, three useful ideas are:
 Use metrics from a "not quite complete loop": set Start and Finish locations very close together, but not identical, and use "Route Alteration" to eliminate the direct route between them while otherwise matching your desired loop, giving "almost complete" metrics - if you want "complete" metrics, add in the short "missing section" Start-to-Finish metrics.
 Sum metrics from "out" and "return" routes: first calculate metrics from the trailhead [Start] to the furthest intersection along your loop [Finish], using "Route Alteration" if needed to match the outbound portion of your loop. - then obtain metrics for the return portion by (after clearing the previous result) keeping the same Start and Finish locations but now using "Route Alteration" to match the return route and mentally swapping the elevation gain/loss values - add these two results together to get the complete loop metrics.
 Create a loop route URL: use the "complex route creation" method described below to create the desired route and obtain its metrics.
|•||Complex route creation: a plot and metrics of any route (e.g. loop with start=end, route with backtracking or crossings or duplicate sections, etc.) can obtained by creating a route URL (i.e. text which can be input into a browser) by those with a modicum of technical skills or geekiness using the method detailed on the creation of URL to display any route webpage.|
|•||Calculations use digitized trail location and elevation information, primarily obtained by local GPS tracking.|
|•||Mileages are slightly under-estimated, since the digitized data use straight-line segments which omit smaller wiggles. They are in good agreement with measuring-wheel-obtained distances in the Sierra Club Trail Guide, but are typically 4-10% smaller than GPS "odometer" mileages (but the latter can include "spidering" around a point while stationary).|
|•||Cumulative upward/downward elevation gain/loss ("ftUP" and "ftDN") calculations use smoothed elevation data for better accuracy and are reasonably consistent with barometric GPS data.|
|•||Historic ("lost") trails are not included in these calculations.|