-- Ay (eos q sin c sin x 4- sin @ cos x)) do + 
C 
— fcos x (x sin 9 + h cos ¢)? + y eos o sin x (x cos o — h sin ¢ 
D: } y } } 
+ sin p cos @ sin w sin x (x? — A?) -- y? cos x T 
-- hz sin c cos 2 g sin x) dw + 
C 
+ D {x (eos o cos x — sin q sin c sin x) — y cos e sin x — 
— h (sin p cos x + cos o sin o sin x)} dx (17) 
3. Terrestrial photogrammetry 
In terrestrial photogrammetry the coordinate systems, translations 
and rotations usually are arranged in accordance with fig. 4. From 
a comparison between the figures 2 and 4 it is evident that the pro- 
jective relations of terrestrial photogrammetry can be derived directly 
from the corresponding formulae systems of aerial photogrammetry 
(expressions 5—6 and 14—15) after the substitutions y' —2', y —2 
and h y. 
Consequently the differential formulae (8), (9), (16) and (17) ean 
be applied to terrestrial photogrammetry after the substitutions just 
mentioned. We therefore refrain from writing these differential 
formulae for terrestrial photogrammetry. 
4. Some applications of the differential formulae 
The differential formulae can be regarded as linearizations of the 
more complicated complete projective relations, which are very heavy 
to handle. The complete differential formulae can be developed around 
arbitrary values of the nine parameters. 
There are many important applications of the differential formulae 
to various problems, in particular in photogrammetry. The correct 
treatment of the theory of errors, for instance, necessarily requires 
that linear differential formulae are derived which express the pro- 
pagation of the errors of various factors.