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  1. #1
    squale Guest

    Finding exact elevation of my house?

    Does anybody know how you would go about finding the exact elevation of your house? My little handheld Garmin eTrex told me I was at about 1700feet MSL, but that keep varying by like as much as 25-30 feet while just standing in my driveway. So I was wondering if there is a better way to know for sure what your exact or very close to exact elevation is?

    I live at the top of a mountain in Jersey and I have 1 airport 5 miles away and another 9 miles away and ALWAYS have small aircraft traffic above my house, so I was going to look into getting a scanner so I can listen into what's going on. Both of the airports are UN-controlled though. In fact, I don't know for sure, but I might be able to get some other airports like 10 miles or more away since my house sits pretty high..

    Thanks

  2. #2
    Join Date
    Jan 2003
    Location
    Flying at Mach 0.30
    Posts
    8,366
    Check the mortgage survey.

  3. #3
    squale Guest
    great idea,,, do you know if this is 100% accurate?

  4. #4
    jfitzpat Guest
    Just how precisely are you trying to measure? Depending on the age of a mortgage survey and the method used to make it, precision will vary. It will generally be better than a non-WAAS GPS receiver for elevation, but it won't be perfect.

    -jjf

  5. #5
    Shaun Guest
    go to the county seat and get a topographic plot map of your tract

  6. #6
    Join Date
    Jul 2002
    Location
    KBFI, Seattle WA
    Posts
    2,032
    That little GPS may be more accurate than you think. I have the eTrex Legend, and it can calculate the elevation barometrically. If there is an elevation that is known near you, then go there, calibrate the barometric altimeter, and return to your house. That should be pretty darned accurate. Otherwise, if you have a WAAS (Wide Angle Augmentation System) then the GPS calculated altitude is also pretty accurate. A difference of 20 feet isn't bad, all things considered. Why do you need such an accurate elevation??

    Jordan

  7. #7
    Join Date
    Oct 2002
    Location
    GHG (Marshfield, MA)
    Posts
    2,320
    http://www.topozone.com/default.asp?404;http://www.topozone.com/findresults.asp

    Some of the topos are metric (check to see yours are in feet and not meters). Type in your address and pull down the Topographic map.

  8. #8
    charliefoxtrot Guest
    I agree with Jordan. The survey you usually get for a residential closing is, frankly, what you pay for. If they were very carefully reseached and field verified, they would cost way more that $300. The elevation data is usually just enough to verify that you don't lie in a flood plain. I'm not knocking surveyors, it just the scope is limited for a house plat. If you got a full topographic survey for your property (approx $1,000/acre, your milage my vary) THEN you would have a reliable document.

    Topographic maps, such as USGS Quad maps are probably not detailed enough for your property.

    Stick with your gadget but hire a surveyor if you wallet is stronger than your curiousity.

    BTW, I'm not a surveyor nor do I represent the Registered Land Surveyors Association. Just a free plug!

  9. #9
    Your house would be at zero AGL. The property surrounding it would be another matter.
    Last edited by JimJenson; 04-15-2005 at 23:13.

  10. #10
    Join Date
    May 2004
    Location
    Baltimore, MD
    Posts
    4,932
    I've never verified, but "have heard" that taking a series of GPS measurements over an extended period of time and averaging them can yield very accurate results.
    -harry

  11. #11
    jfitzpat Guest
    Originally posted by hm
    I've never verified, but "have heard" that taking a series of GPS measurements over an extended period of time and averaging them can yield very accurate results.
    -harry
    That is true. However, it won't work everywhere - for example, if you are in a valley, you never get very good angles on the sats in view.

    -jjf

  12. #12
    Reds_bear Guest
    I'd still interpolate on a USGS topo of your section. Even if the elevation lines (iso somethings...i'm blanking) are 50 feet, you can get an idea. Also, lakes are usually precicely elevated, try to judge your elevation from them.

    Barry


 

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