Results 1 to 3 of 3

Thread: Getting altitude data

  1. #1
    Junior Member
    Join Date
    Jun 2008
    Posts
    1

    Default Getting altitude data

    If the terrain layer is checked, latitude, longitude and altitude are displayed on screen for a Place. If you want to recover latitude and longitude you can unzip the kmz file to the default doc.kml or you can name the kml file for example to Place.kml. Then you can open the kml file in a wordprocessing program or cat or more or less it in UNIX.

    However, only latitude and longitude are given in the kml file. The altitude value is always zero.

    Nevertheless, altitude is displayed in GE in the bottom margin of the view, to the right of latitude and longitude.

    Where is GE getting the altitude information, and is this recoverable from the kmz file or elsewhere?

    The reason for my question is that I want to estimate the historical occurrence of malaria from altitude data, since low lying areas are more likely to have malaria.

    Thanks.

    Gene

  2. #2
    Super Moderator Munden's Avatar
    Join Date
    Aug 2006
    Location
    Maryland, USA
    Posts
    939

    Default

    Google Earth displays the altitude from the terrain data they have stored. However, placemark altitude is not the same. As far as I know, the only way to get the terrain altitude is by moving the cursor around 'live'. The placemark altitude is a mechanism used to make things easier on the users.

    Because GE can have terrain on or off, they needed a way to let the users define how high a placemark is without having to list it in an absolute manner on each placemark. An absolute placemark altitude means some placemarks might be floating in the sky if terrain is turned off, or might be 'buried' into the ground if terrain is turned on.

    The altitude tab on the placemark editing window might help me explain.

    Your options are 'Clamped to the Ground' which means of course that the altitude is zero. 'Relative to the Ground' means the altitude is simply added to whatever the terrain at that point is. Of course now your placemark will only show that relative to the ground. 10m. 0m. 100m .. whatever you choose to set it to.

    The final one, 'Absolute' simply lets you set the placemark's altitude to whatever you choose, no matter if terrain is on or off. Of course this is entirely manual, so you'd have to use the altitude display in the window to know how high to set it.

  3. #3

    Default

    I think the altitude stored in the kmz file is altitude above ground level. The altitude shown on the screen in google earth is above sea level. I don't think there is anyway to do what your are trying to do with Google Earth.

    But you might try this.
    http://www.nearby.org.uk/elevation-kml.php

    Another option would be the KML file at this website.
    http://srtm.csi.cgiar.org/

    This will overlay google earth with colored map showing altitude. YOu can plot your malaria data on top of this and visualize the relationship between the data and th elevation.

    Good Luck.
    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
  •