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Survey Requirements

Ground control survey is required for any mapping project, in most cases the client utilizes their in house survey staff, if you require these services P.T.I. can recommend competent individuals licensed to do ground surveys by conventional survey methods or by use of GPS survey.

Either way P.T.I. will ensure that the density and location of the horizontal and vertical control is properly established to maintain the project order of accuracy.

On large or remote land masses a combination of ground survey and analytical photogrammetry can be used to minimize costs with no loss of accuracy. P.T.I. will verify all horizontal and vertical ground control by means of analytical triangulation.

A computer printout showing the final deviations between ground and photo position for each point is available as proof of ground control accuracy.

TARGET DIMENSIONS
Positional accuracy is a function of ground control survey accuracy and how close the photogrammetrist can measure to the same image point on the photograph.

Because of this the target shape, dimensions and clarity are extremely important in the flight planning process, the target is composed of white painted strips in the form of a "T X Y L of V". These paint strips should be positioned clear from building overhang and clear from tree cover as much as possible.

Ground control survey using Global Position Systems (GPS) must have a clear line of sight to 15 degrees from the horizon making choice of target locations a critical part of the overall control network design.


 Photo scale

 Target Diameter
in feet

 Target Width in Inches

 1"=200

 1"=250

 1"=300

 1"=333

 1"=400

 1"=500

 1"=600

 1"=700

 1"=800

 1"=1000

 3.0

 4.0

 5.0

 5.5

 6.0

 7.0

 8.0

 9.0

 12.0

 15.0

 4.0

 4.5

 5.0

 6.0

 7.0

 9.0

 10.0

 12.0

 15.0

 18.0

 

 
 
103 Washington Street, Po. Box 349 Weymouth, MA 02188 Tel:: 781-335-7229 Email: sales@ptimapping.com