Mt. Whitney Portal Store & Hostel Forums General Mt. Whitney Portal Store Message Board GPS

I'll be flying over next week from the UK to part walk the JMT.Then off to Lone Pine and a day walk up Whitney.What I would like to know is what settings to apply to my GPS,for this visit?Oh,I'm using Tom Harrisons map pack for the trip.
Thanks,Macdee.

Are you thinking datums? Most of our US-map work is done with WGS84 datum. Check the legend on your Harrison map to verify this. If you want Mt. Whitney as a reference on your flight, you can enter 36.57845 degrees north latitude and 118.29217 degrees west longitude, but you will need a window seat, with your GPS unit right at the window, and it would be best to ask the flight attendant if it is okay to use your GPS. American Airlines does not allow GPS units to be used in flight, but many of the other airlines do.

If you would like "settings" for the main trail, <a href=http://www.whitneyportalstore.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=004475>click here</a>.

Tom Harrison's maps use the WGS84 datum. Set your GPS accordingly. Note that the 7.5 minute maps issued by the U.S. Geologic Survey (USGS) use the NAD27 datum. The difference in position for an incorrectly set GPS can be as much as 100 meters. Any quality map will specify which datum it uses somewhere in the map legend. The Pacific Time Zone is currently on Daylight Savings Time. This is 7 hours behind GMT. Good luck!!

Thanks for your prompt reply guys.Yes it's the datum info I was requesting! I dug the Harrison maps out my rucksac and checked out the legend on the front.Looks like NAD 27 used on this pack.Am I right in thinking the magnetic declination for California is 14.5 degrees East?Just want to make sure I get it right!!
thanks again,macdee.

According to NOAA, the declination for Whitney is 13 degrees 40 minutes west.

http://www.ngdc.noaa.gov/seg/geomag/jsp/struts/calcDeclination

The John Muir and Whitney trails are well marked and you won't need your GPS unless you plan to do some some off trail exploration. There are a fair number of hikers on these trails as well, especially the main Whitney route. A friend just completed the JMT and said practically all the snow is gone and the stream crossing were never higher than his knees.

BTW, I use my GPS to collect waypoints, and for a margin of safety.

many thanks for all the info.gps up and running!

..macdee

Took my toy with me this past week on a four day around Whitney. Haven't yet had time to look at the details but had it on up the North Fork to UBSL, Thor, Iceberg, up the JMT/west side to Trail Crest and down to the Portal.

Had pretty good readings the whole way, excepting tree coverage and places where we were walking against shear granite walls.

Interestingly two GPS's on the trail had greatly different coverage abilities. Didn't really use them to navigate as much as collect data. Couldn't see getting lost anywhere in the zone. Having a trip that we were in no hurry (day hike) we enjoyed the explorations off trail.

Conversed with Doug Sr about GPS's a little and came to the same conclusion. It's silly to be using them for accuracy and safety in many places. Sitting on top Thor my GPS Topo showed the peak offset a few feet. Of course that few feet meant a free fall on the South side of 1500 feet

Also saw a few other people with GPSs hanging off their belts, clips. But not one woman???

I guess they don't get lost as easily...

I would definitely bring my GPS and probably pre-load in a track of the Mountaineer's Route, so it'd be easier to follow. I'm sure someone on the Internet could furnish an accurate .gpx file of the route.

I love my Garmin 60CSx and would bring extra batteries for it and just deal with the extra ounces. It so worth it to me.

Yes will take my gps along.Use it for waypoints I think.Handy for spot heights!

About the only thing a GPS is good for on the Whitney trail or the North Fork trail is the elevation reading. Both trails are obvious and almost imposible to get lost on, unless you wander off trail while staring at your GPS. Bring them but dont forget to look up from the GPS and the trail and enjoy the scenary.

I seem to recall a quote from Wayne Pyle stating that you can't rely on the elevation reading from a GPS. Maybe he can chime in with an explanation.

Well, you can't rely on the GPS elevatin reading being 100% accurate, but it is usually reasonably close. I think most use barometric altimeters, so that causes some variability in the readings. I have a Garmin 60CSx and it is usaully accurate to within 100 feet..probably a bit better than that, but it does vary.

Here are some actual data.

I compared my GPS readings with "official" elevations for 51 points along the John Muir Trail, including Whitney, Trail Crest, Trail Camp, Mirror Lake, and Whitney Portal. The average deviation of my GPS reading from the expected value was 0.1% (which would be 14' on the summit of Whitney). The maximum and minimum deviations were 2.4% and -2.4% (which would be 350' on the summit of Whitney -- for the record, my reading on the summit of Whitney was 14456').

Of the 51 data points, 38 were within 1% of the expected value (1% would be 145' on the summit of Whitney). I am still in the process of playing with my hike data. It is possible that a couple of the readings could be in error because the spot I recorded was not precisely the spot I thought I was recording.

My GPS is a Garmin eTrex Vista Cx. It does have a barometric altimeter. I once knew how my old eTrex Summit used barometric vs. GPS data, but I have long since forgotten.