Altitude/Elevation readings from a 276c

Discussion in 'Mapping & Navigation' started by PASSMORE, May 5, 2005.

  1. PASSMORE

    PASSMORE Just the last name...

    Joined:
    Apr 9, 2004
    Oddometer:
    4,254
    Location:
    The Texas Embassy in Sloughhouse, CA
    I am in need of some altitude/elevation readings... Seems this would be a terrific "excuse" to pick up a 276c that I have been coveting :evil

    In what incriments does the 276c give these in? Have you found it to be accurate (to what +/-?).

    Thanks in advance for your comments.
    #1
  2. FatChance

    FatChance Road Captain

    Joined:
    Jun 12, 2003
    Oddometer:
    11,625
    Location:
    Durango, Colorado, USA
    As for accuracy, I would expect the elevation error range to be about the same as the position error range, or accurate to within about 15 feet?
    #2
  3. Eurobiker

    Eurobiker Vintage Cat Herder

    Joined:
    Apr 23, 2002
    Oddometer:
    6,051
    Location:
    Albuquerque, NM
    Your vertical accuracy is about twice the horizontal accuracy. So if you're good to 10 ft. horizontal, it'll be 20 ft. vertical. The relative accuracy of 2 points will be much better though. So if you want to know the delta height between 2 points, it's generally much better.

    I just fired up my eMap and it showed my elevation at 5815 ft. with an accuracy of 16.8 ft. If you're out and find a USGS, FS or BLM benchmark with the elevation stamped on it, set your GPS receiver on the marker for an emperical check.
    #3
  4. Bill the Duck

    Bill the Duck Unwitting Accomplice

    Joined:
    Oct 27, 2002
    Oddometer:
    10,856
    Location:
    Scottsdale, AZ
    May I heartily recommend GARMIN. See my recent thread in this forum.

    BTW, I saw a 276c on JKAM's V-Strom last weekend. Quite readable even in direct sun. Cool features too. :thumb
    #4
  5. txrider

    txrider Been here awhile

    Joined:
    Mar 14, 2005
    Oddometer:
    370
    Location:
    The great state of Texas
    276c is a nice piece of gear, the only other contender is the 2610.

    I would say the 20ft mentioned earlier is about right for accuracy, at least what the GPS reports.
    #5
  6. Manuel Garcia O'Kely

    Manuel Garcia O'Kely Back at last

    Joined:
    Apr 5, 2004
    Oddometer:
    15,213
    Location:
    Central Colorado Rockies
    Yea, vertical accuracy is good....HA - I've driven across the Golden Gate Bridge and been told that I was a submarine - at -30 feet.

    IF you are getting the WAAS signal and have it activated, accuracy improves but I'd say +/- 50 feet is more the rule - but who cares? That's close enough. Unless you are making a landing IFR and it's Zero-Zero [0' ceiling and 0' horiz. visiblity].
    #6
  7. HardCase

    HardCase winter is coming

    Joined:
    Mar 25, 2004
    Oddometer:
    11,893
    Location:
    Griz Country
    I've noticed that my elevations readings can sometimes change when I'm sitting still. I gather that means that the satelites are moving around in space? In any case, my comparison of GPS versus Forest Service markers or USGS elevation points is that the GPS is no better than a + or - 50 feet at any given time. That's close enough for my purposes.
    #7
  8. BurnieM

    BurnieM Nipple boy

    Joined:
    Sep 24, 2003
    Oddometer:
    4,104
    Location:
    Sydney, Australia
    We generally say that horizontal accuracy is 5-10 metres (15-30 ft) with WAAS off.

    Vertical accuracy is 10-50 metres (30-150 feet). This is a 10-20 metre error plus up to a potential 30 metre discrepancy due to differences between the model used to calculate height and the true shape of the earth.
    #8
  9. TiWorld

    TiWorld John

    Joined:
    Apr 18, 2004
    Oddometer:
    201
    Location:
    DFW / WW wanderer
    When I drive along the coast highway, my 276c says I'm roughly -35 ft., -- snorkel territory. I'll call Garmin and see what they say, but I've found altitude to be pretty far off,... maybe it's just my unit.
    #9
  10. pbansen

    pbansen Hosehead

    Joined:
    Jul 8, 2001
    Oddometer:
    435
    Location:
    Truckee, California
    I'd agree that vertical readings generally seem to have twice the error (at least) compared to horizontal position. On the other hand, every day on the way to work, I pass a 6,000 foot elevation benchmark. For a while, I was keeping my Garmin 76C in the car on a windshield mount and I'd fire it up when I left the house in the morning. As I'd pass the 6,000 foot marker, I'd glance at the GPS to see what it said. More often than not, it would be within a couple of feet, which I find amazing, because at other times it was 70 feet off of a known elevation...
    #10
  11. Gerg

    Gerg Gergy Bear

    Joined:
    Dec 25, 2001
    Oddometer:
    8,765
    Location:
    Left Coast
    Mine is +/- 50 feet. I usually do the checking by the altitude markers that CalTrans puts oout. And knowing CalTrans, THEY are probably 50' off.

    Gerg
    #11
  12. rikkitik

    rikkitik More toys than time!

    Joined:
    Apr 24, 2005
    Oddometer:
    52
    Location:
    Tuscaloosa, AL
    Greeting,


    Elevation accuracy with any GPS unit is dependent on the number of satellites you manage to track at a given moment. I use a Garmin SPIII+ and the error is rather small when I have a full compliment of signals to track. IT is NOT as accurate as a location - remember that thing is trying to compute elevation is 3D mode.

    Even the best units I used while playing professional soldier has some elevation errors although locational were good to +/- 1 meter. Heck, 3 feet is pretty close - especially when close does count in horseshoes and hand grenades.

    Rikkitik
    #12
  13. BurnieM

    BurnieM Nipple boy

    Joined:
    Sep 24, 2003
    Oddometer:
    4,104
    Location:
    Sydney, Australia
    'Don't sit so close together. One grenade will kill you all'

    :D
    #13
  14. TiWorld

    TiWorld John

    Joined:
    Apr 18, 2004
    Oddometer:
    201
    Location:
    DFW / WW wanderer
    FWIW, I called the friendly Garmin support line. Was told that the 276c elevation accuracy is +/- 100 feet.
    #14
  15. PASSMORE

    PASSMORE Just the last name...

    Joined:
    Apr 9, 2004
    Oddometer:
    4,254
    Location:
    The Texas Embassy in Sloughhouse, CA
    Dammit! Was hoping I could "get by" with one to get a base floor elev. for our building project. +/- 50 feet ain't gonna cut it for that....

    Damn.... :cry
    #15