PHOTOGRAMMETRIC ENGINEERING
Technology (2 triangulations) and that of The
Ohio State University* (5 examples) indicate
clearly that the Cross Bases Method yields
practically the same accuracy as the classical
(coordinate) method.
Compared with the classical methods used
in ground-control, the Cross Bases Method
has the enormous advantage that it is not
dangerously affected by the eventually unde-
termined deviation of the vertical.
In regions without geodetic control, this
method is the only one—to the best of the
author's knowledge—that can yield accepta-
ble results. Also, in regions with geodetic con-
trol, the Cross Bases Method could be used
either by itself (yielding practically the same
accuracy as the classical methods of ground
control) or in combination with one of the
coordinate methods. In the latter case, there
is no doubt than an accuracy superior to that
* These tests were conducted by the author and
made possible through research grants from the
University of Illinois Research Board.
of any single method will be attained. Studies
are currently underway at the University of
Illinois to determine the practicability and
accuracy of such a combination, and also to
extend the use of Cross Bases Method in
block triangulations.
REFERENCES
1. Karara, H. M, "Fehlerfortpflanzung und Aus-
gleichung von Aerotriangulationsstreifen mit
Gemessenen Querstrecken," Diss. E. T. H.
Zurich, Switzerland, 1956.
2. Karara, H. M., “Cross-Bases Method in Aerial
Triangulation,” PHOTOGRAMMETRIC ENGINEER-
ING, Vol. XXIII, No. 5, December, 1957.
3. Karara, H. M., “About the Character of Errors
in Spatial Aerotriangulation," PHOTOGRAM-
METRIC ENGINEERING, Vol. XXV, No. 3, June,
1959.
4. Schermerhorn, W., “Results of a Pre-War Aerial
Triangulation of Large Area, Photographed for
Geological Purposes," Anales de la IV Reunion
Panamericana de Conulta Sobre Cartografica,
Buenos Aires, 1948.
Roelofs R., “Astronomy Applied to Land Sur-
veying," N. V. Wed. J. Ahrend & Zoon, Amster-
dam, 1950.
Un
