Results 1 to 7 of 7

Thread: How accurate is elevation on google earth, and how is it measured?

  1. #1
    Junior Member
    Join Date
    Dec 2011
    Posts
    1

    Default How accurate is elevation on google earth, and how is it measured?

    I'm trying to find accurate elevation data for our area, but I'm not convinced about how accurate Google earths elevation is. Has anyone else checked it? How is it measured, and how accurately is that info coordinated with the map? Are there any other sites or sources out there that have accurate elevations?

  2. #2
    Moderator Emeritus Appletom's Avatar
    Join Date
    Jul 2005
    Location
    El Paso, Texas
    Posts
    1,278

    Default

    Airport runway elevation is the only place I know of where elevation would be easily findable online and easily comparable to Google Earth.

    Just did a quick test with El Paso International Airport. According to FAA data, runway 4 is 3,916.6 feet ASL. Google Earth shows it as 3,921 feet ASL. (Measuring on the number itself, not sure if that's where the FAA measures from.)

    Runway 22 is 3,949.2 feet, Google Earth shows it as 3,950. (Oddly enough, runways aren't flat.)

    Denver runway 8 is 5,354.3 ASL, Google Earth shows it as 5,358.

    DFW runway 35L is 566.5, Google Earth has it at 560.

    So - I'm seeing variances of 1-7 feet.

  3. #3
    Member Crane's Avatar
    Join Date
    Aug 2008
    Location
    Rio de Janeiro
    Posts
    60

    Default

    For most people, that's very accurate. Surprised me.

  4. #4

    Default

    There are several possible sources. Most likely they are using elevation data from the Space Shuttle SRTM mission, which has 90 meter spacing for most of the world. I believe it has 30 meter spacing for the US.
    Matt Fox

  5. #5
    Junior Member
    Join Date
    Feb 2012
    Posts
    1

    Default Give attention.

    I have read postings that they are also using 10m spacing but thats not confirmed. Maybe only at some special areas.

    On a plain surface 90m is fine. But take attention, in high mountain areas the GE elevation is not very accurate. I got a 10m spacing laser-scan modell from my country and I just checked it with the GE elevations.
    On a plain area the difference is around 0 -3 meters
    On steep hills the difference can be 100 meters (> 300 feet)

    If I calculate a 100m spacing elevation modell out of the 10m one, then the difference for the same place could be 60 meters.

  6. #6
    Junior Member
    Join Date
    Aug 2010
    Posts
    5

    Default Runways not flat

    I spend a lot of time in the F-16 cockpit. American runways are reasonably flat, whereas runways in other countries are really a challenge. I am wondering if GE puts the raw elevation data of American runways through some kind of algorithm that flattens them out? If so, that should be applied universally to all airports in the world. It is not necessary to go into flight mode, just put the street view man on a runway in Athens or Tel Aviv, look around, and compare it to Dulles Airport in Washington for example.

  7. #7

    Default

    The elevation data available for the US is more accurate than the rest of the wold. That's probably why runways in US look different than rest of the world.
    Matt Fox

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •