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Map Accuracy Standards

Photogrammetric mapping from aerial images is a proven science, the positional accuracy is easily predicted when standard constants are met:

1. calibrated precision 9" x 9" aerial camera
2. proper flying height above mean terrain
3. Precision photogrammetric stereo-plotter
4. reliable ground control survey and well defined targets

P.T.I. provides mapping that will comply with accuracy standards for large-scale maps as developed by Specifications and Standards Committee of the American Society for Photogrammetry and Remote Sensing (ASPRS).

HORIZONTAL MAP ACCURACY is defined as rms error in terms of projects planimetric survey (x,y) for checked points as determined at full (ground) scale of the map. The rms error is the cumulative result of all errors including those introduced by the process of ground control surveys, map compilation and final extraction of ground dimensions from the map. The limiting horizontal rms errors shown below for Class 1 maps are the maximum permissible errors established by this standard for tests on well defined points only.

 

 Delivery scale

 Standard error

 CMAS

 Maximum Error

1"= 20'

1"= 50

1"= 100'

0.20

0.50

1.00

0.43

1.10

2.10

0.60

1.50

3.00

 VERTICAL MAP ACCURACY is defined as the rms error in the elevation in terms of the project's evaluation datum for well defined points only. For Class 1, maps, the limiting rms error in evaluation is set by the standard ine-third the indicated contour interval for well defined points only. Spot elevations shall be shown on the map within a limiting rms error of one-sixth of the contour interval.

Contour Interval

Standard error

 VMAS

 Maximum Error

1.0

2.0

5.0

0.30

0.60

1.50

0.50

1.00

2.50

0.90

1.80

4.50

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