SIGNALISIERUNG, PASTORELLI 141 
Katastervermessungen. (Sechzig Punkte bei schwierigem Gebirgsgelände, 250 Punkte 
bei flachem einfachen Gelände.) Diese Leistung ist allerdings nur bei Verwendung von 
Kartontäfelchen erreichbar. Wenn Metallplatten, Gipsringe usw. verwendet werden, 
kann dieselbe Leistung nur durch Einsetzen von einem Techniker mit drei bis fünf Hilfs- 
kräften eingehalten werden, bei einer wesentlichen Verteuerung der Signalisation. 
Werden die oben angeführten Regeln der Erfahrung beachtet, dürften bei der 
Auswertung nicht mehr als 3% der signalisierten Punkte ausfallen. Die Ausfälle müssen 
im Einblick auf die Einschrankung der kostspieligen Ergänzungsaufnahmen im Gelände 
so klein wie möglich gehalten werden. 
THE SIGNALISATION OF CONTROL POINTS AND BOUNDARY BEACONS 
IN PRECISION PHOTOGRAMMETRY 
The problems of signalisation for cadastral and for topographic surveys are dis- 
cussed. Since setting errors are greater than those due to photogrammetric measurement, 
signals should be sharply and clearly defined in the photographs. 
For cadestral surveys in easy terrain the various signals used are described (card- 
board, metal or plastic sheets: or top of boundary stone painted white). Signals can be 
recovered after photography. The importance of landowner cooperation is stressed, par- 
ticularly in reallocation surveys, where a large number of old beacons must be found and 
signalised in a short time. In mountainous country, recovery of signals after photography 
is impractical, and cardboard markers are therefore recommended. 
Signals for topographic surveys are usually cairns, stone circles, whitewash figures, 
cardboard or aluminium sheets or metal foil strips. 
Signalisation costs are 8 to 12% of survey costs, but the expense of good signalisa- 
tion is justified by the increase in reliability and accuracy of the photogrammetric survey. 
Careful thought in placing signals leads to further economies. The location of auxil- 
iary eccentric stations, and the ground survey, should be such that post-flight checks and 
re-measurements are unnecessary. 
Signals are usually painted white. Signal sizes and shapes depend on flight height, 
picture scale and the size and shape of the floating mark in the plotting instrument. The 
practical formula for determining signal size (d) is 
picture scale number 
dmetres = 40,000 
For cadastral survey, using cardboard sheets, a two-man team can mark about 60 
points in difficult country per day, and about 250 points in easy country. Using other 
signalisation methods, 3 to 5 men are necessary for the same performance. 
Approximate costs per point for cadastral signalisation, determined from 20 years 
of experience, mainly in Canton Tessin, Switzerland, are as follows: 
Cardboard sheets: Fr. 0.35 for material plus Fr. 0.50 to Fr. 1.70 for labour, de- 
pending on slopes and cover (total Fr. 0.85 to Fr. 1.70 or ls 5d 
to 2s 10d). 
Plastic or metal plates Fr. 0.45 for material — assuming plates may be used five times — 
in an easy area: plus Fr. 1.10 for labour (total Fr. 1.55 or 2s 7d). 
Painting boundary Total costs are about the same as for cardboard sheets, but this 
stones: method is only practical in easy country. 
Whitewash circles 
or figures: Total costs are about the same as for plastic or metal plates. 
wy 
re ry mt Hp