Eastern Topographics (e-topo.com)
Eastern Topographics - Aerial photography and topographic mapping of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York and New Jersey.
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Ground Control
Ground Control
In order to do topographic mapping or create ortho photo's it is necessary to have surveyed ground control that are visible in the photography.  Objects such as aerial targets, paint lines, and catch basins or similar are acceptable features.  It is necessary for these points to be visible in at least 2 photos or more in order to view them in stereo.

HV HV - Horizontal and Vertical coordinates on a feature such as catch basin.

V V - Vertical coordinates at a location.  May require X,Y coordinates in addition.

     Green boxes may also appear on the photo and are used for the surveyor to be able to relocate a ground control point if needed.

     Yellow shading may also appear if areas are heavily obscured by shadow or dense tree cover.

Descriptions of the points are provided on the back of the photo to help locate point in the field.