malies in the isobaric surfaces, or turbulances during the photo flight. Scheduling 
the flight under more stable atmospheric conditions, or recording of the pertinent 
meteorological data, should yield smaller altitude errors of the exposure stations re 
sulting in a higher elevation accuracy of the block triangulation. 
If the list of errors of the 20 tests (prepared by the Présidence - cap. VI tab. I) 
is analyzed one can see that certain coordinate errors have the same sign for all 20 
tests. This leads to the conclusion that either the given ground coordinates are 
erroneous, or that there are other systematic error effects present independent of the 
block triangulation method used. Such points should either be eliminated from the 
tests, or the coordinate errors should be reduced by the systematic portion if various 
block triangulation procedures should be compared. 
An efficient use of the block triangulation should also yield adjusted values for 
elements bx, by, bz, m, <p, and x. The availability of these values would greatly reduce 
the time required to set up individual models (relative orientation, scaling, and abso 
lute orientation) for plotting purposes in a I.order or II.order stereoplotting instrument. 
Some tests performed have shown that a time saving of at least 80 per cent can be 
expected per model when, for the set up of the individual models for plotting purposes 
in a stereoplotter, adjusted orientation elements obtained from the aerial triangulation 
are used (adjusted values for bx, by', by", bz', bz", off, co", q/, <p", x', x"). The adjusted 
orientation elements can be computed from the closure errors at the end of the strip 
triangulations (scale closure error, by-, bz-, «-, 9-, x- closure errors). When such adjusted 
orientation elements are introduced into the stereo plotter the model in question is 
nearly correct and very little time is required to correct the model so that the residual 
errors at the points, determined by aerial triangulation, are within the tolerance 
whereupon, the model is ready for plotting. In future tests more attention should 
be given to this important phase of block triangulation. 
When various block triangulation methods, which were applied to the block 
triangulation « Massif Central », are compared, it is necessary to consider the attainable 
accuracy, the required time, and the necessary costs. It is hoped that if such a compa 
rison is made, that realistic critérions or degree of efficiency formulas are established 
which take these three basic factors properly into account. 
The organization of the test « Massif Central » has produced many experiences 
and valuable information and the Présidence of the Group of Study for Experimental 
Researches on Blocks of Strips, as well as IGN in Paris, is to be commended for their 
great efforts to make this international test possible. 
REFERENCES 
[1] A. J. Bra nden berg er, The Practice of Spatial Aerial Triangulation, Photogrammetric Institute, Fe 
deral Institute of Technology, Zurich, 1951. 
[2] A. J. Brandenberger, Some Considerations about Error Propagation in Strip Triangulations-. Attainable 
Accuracy, « Photogrammetria » and « Publication No. 8 », Institute of Geodesy, Photogrammetry, and Carto 
graphy, The Ohio State University, 1958. 
[3] A. J. Brandenberger, Strip Triangulation with Independent Geodetic Controls. Triangulation of Strip 
Quadrangles, « Photogrammetria » and « Publication No. 9 », Institute of Geodesy, Photogrammetry, and Carto 
graphy, The Ohio State University, 1959. 
[4] A. J. Brandenberger, Aerial Triangulation with Auxiliary Data, « Photogrammetria » and « Publica 
tion No. 10 », Institute of Geodesy, Photogrammetry, and Cartography, The Ohio State University, 1960. 
[5] A. J. Brandenberger and S. La gril a, Aerial Triangulation by Least Squares, Report I, II, III, IV, 
and Final, ERDL, Fort Belvoir, Virginia, 1955-1956.