Analytical aerial triangulation is a process which requires a specific order of procedures and rigorous mathematical computations. The steps to this procedure are:

• Preparation of Diapositives
• Scanning of Diapositives (for softcopy method)
• Preview of Control Photographs
• Selection of Model Control Pass Points
• Point Measurement
• Computations
• FAAT Report Generation

At Bradstreet Consultants, our team exclusively uses Fully Analytical Aerial Triangulation (FAAT) and first order analytical stereoplotters, calibrated to within 0.001 millimeter, to take measurements. For the analytical aerial triangulation calculations, we rely on the Analytical Block Aerial Triangulation and Bundle Refinement software by Visual GIANT, a leader in analytical triangulation programs for the mapping industry.

Using the conventional analytical aerotriangulation method, pass point locations are manually selected by reviewing the control photographs with a stereo-viewing device. Using the softcopy analytical aerotriangulation method, pass point locations are digitally selected by reviewing the scanned image on a high resolution video monitor. These digitally located points are used in the final computations to determine horizontal and vertical values. For fully analytical aerial triangulation, individual frames carry a minimum of three pass points; one point near the corner of each neat model, and one point near the nadir position of each photograph.

All ground control points, pass points, and check points are measured with a first-order analytical comparator with an intrinsic accuracy (calibration applied) of at least two micrometers. A local coordinate system is used to locate the control points, pass points, and tie points on each diapositive. All measurements are made utilizing a first-order analytical stereo plotter.

Analytical aerial triangulation calculations are performed using the Visual GIANT Analytical Block Aerial Triangulation System and Bundle Refinement Program. The simultaneous block adjustment of Visual GIANT will process both photo and independent model measurements, incorporate airborne GPS antenna positions as control, and include added parameters for camera or system calibration. Point residual ovals indicate whether any errors occurred during point transfer or measurement, and, if so, allows corrections to be made immediately.

Upon completion of all aerial triangulation work or sub-block portions thereof, Bradstreet Consultants prepares a formal aerial triangulation report for our client. The report documents that the positional accuracy of the model control meets, if not exceeds, these tolerances:

1. The RMS error of the final block adjustment will not exceed 1/5,000 of the flight height.
2. The average of all points will not exceed 1/10,000 of the flight height.
3. The maximum allowable error of any point will not exceed ±1/2,500 of the flight height.