Photogrammetric Notes

The photography used to produce this map was on a scale of 1:24,000, using a Zeiss RMK-A-15/23 camera No. 21220, 152.46 mm focal length. The pictures for the basic 13 sheets were made by Mark Hurd Aerial Surveys of Goleta, California. The photographs for the four sheets along the eastern edge were made by Landis Aerial Surveys of Phoenix, Arizona, using a Zeiss RMK-A-l5/23 camera No. 21178, 152.57mm focal length. These two contractors roughly split the low-altitude photography at 12,000 ft. and 8500 ft. used by Raytheon-Autometrics to map the trails. Lockwood Mapping, Inc. of Rochester, New York did the overall photogrammetry and the 1:2400 contouring of the Inner Canyon area was done by Swissair Photo & Vermessungen of Zurich.

Vertical relief was depicted by 50-foot contours, supplemented by 25-foot contours in the gentler gradients of the rims and the Tonto plateau. The computation of the field data was done by Harry R. Feldman, Inc. of Boston, Mass. using coordinates based on the Arizona Grid datum. The horizontal and vertical photogrammetric model control was achieved through a semi-analystical triangulation program for both the vertical and horizontal solution.

Compilation utilized a Wild A-7 Autograph on which the pencil chuck of the plotting table was replaced by a scribe-point. K & E scribecoat material was used as the compilation base. By use of direct scribing without the intermediate pencil step, a much more accurate reproduction of the character of the terrain was possible.

A number of unusual problems were encountered and procedures to deal with them were developed which will be helpful in facing similar mapping in the future. Often the operators would lose stereo-vision while contouring the high vertical cliffs and had to back up and start the contour-line over again. Deep shadows, even at noon, on the north sides of the vertigenous cliffs made contouring of these areas difficult — and trails were often completely invisible where they passed through these shadows.

The plotting of the trails and drainage were done on different sheets from the contours. This was essential in this unusual project and it resulted in a number of special problems. In many areas because of the bare, and terrain, there were a multitude of drainage-courses, which would have seriously cluttered the sheets if they had all been depicted. The selection of the key courses was often very difficult. Then, when plotting the trails and drainage, the slope was often dropping so rapidly that it was very difficult to synchronize and maintain a precise Z-position, correctly coordinated with an equally-accurate X and Y position. This problem often resulted in a slight lateral shift in the location of the planimetry, which later had to he corrected to fit the contours in the final manuscript which coalesced both sheets. Normally these problems would have been easily controlled on a single penciled manuscript sheet, simultaneously involving drainage, contours and trails.

We owe a special debt of gratitude to Ray Byrne and Keith Adams of Lockwood, John Baber of Raytheon-Autometrics and Werner Altherr of Swissair Photo — and to all of their skilled associates who actually did this intricate and painstaking work.