Monday, December 30, 2013

Measure geodesic distances on Google Maps

As the name suggests, this Measure Geodesic Distance mapplet allows users to measure the geodesic distance between two or more points on the earth's surface using the Haversine formula. The mapplet uses the formulas from this site http://www.movable-type.co.uk/scripts/latlong.html. The measurement points and lines are displayed on a Google Maps backdrop. Users have the option to choose the measurement units of meters, kilometers or miles: the line color can also be set by the user.

Run the mapplet from this site http://dominoc925-pages.appspot.com/mapplets/geodistance.html

Using the mapplet is easy, just do the following:

  1. Click two or more points on the map.

    Vertex markers are displayed, and geodetic lines are displayed between the vertex markers.
    Note I : the segment distance value is displayed at the mid point of the line(s).
    Note II: the total distance value is displayed at the last vertex marker. 

  2. Drag a vertex marker to another location on the map.

    The geodetic lines and vertex markers are updated to show the new distances.

  3. Click on a vertex marker.

    The latitude and longitude values are displayed in an Info Window.
  4. In the Info Window, click Delete to delete the vertex marker.

    The vertex marker is removed and the lines and markers are updated to show the new distances.
  5. To adjust a vertex marker by precision key-in, click on a vertex marker.

    The latitude and longitude values are displayed in an Info Window.
  6. In the Info Window, type in the new latitude and/or longitude values. Click Save.

    The vertex marker is moved to the new location and the lines and markers are updated to show the new distances.
  7. To clear all the markers and lines from the map, click the Clear button in the right pane


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