LOADING THE MAPS:
I prepared for my test drive of the TOPO 24K – WEST by loading the entire park system onto the 512 Meg card for my GPSMAP 60CSx and then loading maps from TOPO USA. Our first stop was going to be the Redwoods National Park and one of the trails we wanted to do was the Tall Trees Grove trail. It did not exist on the map. No biggie though, the trail was just 1 ½ miles long so maybe it was not important enough to be used. Most of our hiking was outside the park so I used the TOPO USA maps.
USING THE MAPS:
We moved on to Yosemite National Park where I wanted to try out the trail routing features. Our first stop was going to be the Mariposa Grove so I sat down at the computer and began trying to make a route. This particular area is unique in that it is had an inner loop, an outer loop, connecting trails and a road that crosses the trails in many places. We wanted to get onto the inter loop trail, go half way and then move to the outer loop. I used the laptop and Mapsource to create the route but was derailed by the selection of road segments for part of the trip. It seems that the road is a valid trail. After several attempts to create the route I wanted I quit and decided to use the unit with no route for this hike. My first impression after getting on the trail was the map was way off but it turned out that the first segment of the inner loop was not shown on the map and I was looking at the map of the outer loop trail thinking we should be there. Once I figured that out and we got to a place where the trail was shown by TOPO 24K, the map seemed to be accurate. This was an area where there was very heavy tree cover so the GPS track showed some deviation from the trail – probably due to the degraded signal.
The real test came the next day when we drove up to Glacier Point and started a 9-mile hike back to Yosemite Valley on the Panorama Trail. I had loaded some waypoints so once at the trailhead I picked a waypoint on the trail and set a route. The routing choice was “follow road” or “off road”. Knowing roads and trails were treated the same, I chose “follow road” and it set a route down the trail. The distance to my waypoint was the same shown in the park literature. Tree cover on the upper part of the trail was minimal so the accuracy of the unit was great. I was very impressed with how closely the GPS track followed the route. There was no rubberbanding to the trail though. Often the track was right on top of the trail. Trail intersections were very accurate also. The route required a turn from the Panorama Trail onto the John Muir Trail but I never heard the unit beep when I approached the intersection of the two trails. We decided to divert to Nevada Falls, about ¼ mile off the route. The unit never protested.
MapSource USA TOPO Screen Capture with Track Overlay
Notice less cotour detail here than from the TOPO 24K screen shots above.
RECORDING THE TRACKS:
The first screen shot shows the Panorama trail switchbacks just before getting to one of the waterfalls. The track was dead on for most of the trail but did waiver somewhat in the switchbacks. Not enough to whine about though. I had the unit clipped to a pack belt and it was right up against my side - I'm surprised it did as well as it did.
The second screen shot shows a track of an obvious switchback that is not on TOPO 24K. I found another one in which the switchback track was opposite that shown on the map. That's about as bad as it got though.
My next and final test of TOPO 24K took place on Yosemite Valley's western loop trail. I didn't set a route but was just carrying the GPS to see how accurate the trail maps were. I was again impressed. At one point in this 6-mile hike the trail was obliterated by some work being done by the park service. We followed what we thought was the trail and found ourselves with no trail to follow all of a sudden. We used the GPS to take us to where it said the trail was and sure enough – it was there. We ran into this situation again when the trail had been erased by high water and the unit helped us pick the trail up later one more time.
While useful on our day hikes, TOPO 24K would be great to use on multi-day hikes over long distances where the trails are not marked with signs. I think the best way to use TOPO 24K is to download as many waypoints and pre-generated routes as you think you might need. You can create waypoints on your GPS unit on the fly but it's tedious work – you really need to pre-load them if at all possible. Remember, TOPO 24K ends at the park border. If your hike takes you outside the park you'll need something like TOPO USA for the rest of you hike.
In summary, TOPO 24K was worth the price. The trail maps were very accurate and the routing feature allowed us to see how far it was to the end of the trail – or to the next waypoint. When you use this map product with a highly sensitive GPS unit like the GPSMAP 60CSx that holds lock under heavy tree cover, you will get great results.
Comparison of the 24K Map to the Older
USA Topo Map
MapSource USA Topo Map of Yosemite Valley
MapSource US Topo 24K National Parks Map of Yosemite Valley
Good hiking! -Mel