How to use the GPS files?
Each route has at least two GPS download files, one with a waypoint approximately every quarter mile, and the other with the maximum waypoints required to define the freehand trace describing the route. A third GPS download may be included with waypoints for just the key features described in the notes.
The waypoint files are comma delimited text, formatted as follows:
Waypoint Name, Latitude Degrees (DD), Latitude Minutes (MM.mmm), Longitude Degrees (DDD), Longitude Minutes (MM.mmm), Elevation (feet), Date MM/DD/YYYY, Local Time: HH:MM:SS
How accurate are the notes/distances?
I have ridden all of the documented rides many times - most at least 10 times. When capturing a route all miles are taken from the cycle computer which has previously been calibrated against the GPS over a straight and level street ride. Depending on the route complexity I will sometimes capture the highlights once, then return to verify the notes and refine the details before publishing. When repeating rides after publishing I will usually verify the miles/notes are still accurate. Usually the GPS and cycle computer agree within 0.5% - over the last 12 mile route I recorded, the two differed by only 0.01 miles. I find mapping software gives slightly different results to the GPS, so try and use a consistent method for capturing the miles - if yours differ they should at least differ consistently! For some rides the starting point will vary slightly with each visit. I recommend making note of the difference between your mileage and that given for the first feature. Provided your computer is calibrated it should then be a simple matter of adjusting each waypoint thereafter by the offset noted at the first. And at the end of the day it’s fun to explore - so what if you disconnect from the directions - enjoy exploring different paths but please share so we can do the same :)
Why two times?
For each ride I note in the Ride Log section both a ‘Pedal Time’ and ‘Elapsed Time’. The former is the most useful when planning a ride - it’s the time spent on the move, taken from either the cycle computer or GPS (they are usually within a few seconds of each other). If you do a couple of rides and compare your ‘on-the-move’ time with these numbers it will give you a general gauge for how much to adjust the times of other rides to match your fitness level. These are by no means the fastest times the rides can be done in.
The Elapsed Time is simply the difference in time from leaving the car to returning. It’s of interest for planning since it gives an indicator of how much time you might be idle resting. City rides may have time spent waiting for traffic or lights, while rides with steep climbs are going to have longer rest periods. I use this time as the guide for letting loved ones know when to expect me back.
What GPS and settings are used?
I use a Garmin 76CSx for all of the traces. Rather than use the cycle mount I prefer to carry it in a standard camera case to protect it from dust, water and in case of a fall.
The unit uses atmospheric pressure for altitude measurements. Since the start of 2008 I calibrate the altimeter at home based on the local atmospheric pressure and known altitude. Traces recorded prior to then used the default setting, which would rarely if ever have been accurate. This means the starting and maximum elevations may have been wrong, but the distance climbed should still have been accurate. However, I’ve also found significant difference between the GPS estimate of total ascent and that given by Topo! I’m not sure why there is a discrepancy, but for consistency now quote the GPS values for all elevation related measures.
For accurate measurements I have the WAAS/EGNOS setting enabled, although based on the traces overlaid on topographical maps the tracks were usually very accurate even before using this setting.
I also turned off the ‘Lock on Road’ setting as I found occasionally when riding on a cycle path adjacent to a road that the unit would lock onto the road rather than sticking with the trail.
For the map datum setting I use WGS 84, as this is what the topographical maps are based on.
What are the .tpo files?
These are exports from Topo! version 4.2.7, the software used to create the topographical maps. They provide the most complete trace of each route. For more information on this application go to National Geographic