252
1. The orientation bearings should preferably be three in number.
Two of these should form an angle of on either side of the inter
secting bearing <j>LP; the third bearing should be approximately
equal to (jq P.
2. The lengths d of these lines should be such that
1.5 d-[ p <C d <d 3*0 d\ p
where dÏP is the distance between the occupied station I and
the unknown station P.
The variance or the weight may then be estimated with the formula
(48)
where <j2 =-the variance factor
wi.p the weight of the bearing rjq P
n'i the variance of the observations at the occupied
station
p 206265 sec of arc or 636620 cc
c —a. constant pertinent to the accuracy of the existing
control survey (c 3 for an extreme accuracy;
c 6 for a "middle" accuracy and c 12 for a low
accuracy)
The centroid condition does not need to be satisfied.
Bibliography
w\.p
[1] J. M. Tienstra Over de invloed van fouten in de gegeven punten op
het gewicht van de richtingen bij de Puntsbepaling.
Tijdschrift voor Kadaster en Landmeetkunde 1934, P- 101
[2] Manual of Cadastral Surveys of the Netherlands (H.T.W.).
[3] P. Richardus Triangulation and Traversing as a means of measure
ments of small movements.
Report presented at the 6th Congress of the Institution of Surveyors,
Australia, Adelaide, March 1962 (to be published).
