DEFLEC12A for Google Earth (DeflecGE)

This page describes a free application that runs in the Google Earth desktop client. Please install Google Earth, download DeflecGE, and return to this page to learn more.

DeflecGE is a graphical front end for the NGS online tool, DEFLEC12A. It eliminates the need to input geodetic coordinates and displays the deflection of the vertical and horizontal Laplace correction in a placemark balloon. Uses of vertical deflections include geodetic to astronomic coordinate transformation and astronomic to geodetic azimuth conversion (Featherstone, 1999).

  1. Position the point of interest (POI) in the center of the view. One way to do this is to double-click an unmarked location. To precisely position the POI in the center of the view, add a placemark at the desired location; then edit the properties of that placemark and reset the view (explain). For best results, disable automatic tilting (Tools, Options, Navigation, Do not automatically tilt while zooming) and minimize elevation exaggeration (Tools, Options, 3D View, Elevation Exaggeration, 0.01).
  2. Check the box beside the Vertical Deflection network link. A form will be presented with read-only geodetic coordinates corresponding to the view center and input fields for an astronomic azimuth in degrees, minutes, and decimal seconds. The near-geodetic Laplace azimuth, astronomic coordinates, North-South (ξ) and East-West (η) components of the deflection of the vertical, and horizontal Laplace correction are displayed when the Convert button is pressed.
  3. On subsequent uses, reposition the POI and ensure that the network link is checked and selected. Then choose Refresh from the Edit menu, or right-click and select Refresh in the context menu (explain).

Image NGS

Coverage includes the conterminous United States, Alaska, Hawaii, Puerto Rico, the Virgin Islands, American Samoa, Guam, and the Northern Mariana Islands. Check the Extents folder to display the coverage area bounding boxes.

Note: To save DeflecGE results from one Google Earth session to another, right-click on Saved Placemarks and select Save to My Places.

All data are retrieved from remote servers. Data errors, accuracy, and availability are beyond the control of this application.