6.
First-order triangulation requires that sets of observations made on different stations (normally
16 positions of the horizontal circle) be performed___________________________________________.
A.
Once a night for one night
B.
Twice a night for two nights
C.
Each of two nights, with a minimum of 2-hour separation between the two sets.
D.
Each of two nights, with a minimum of 1-hour separation between the two sets.
7.
T h e d i f f e r e n c e b e t w e e n t h e a p p a r e n t a n d t h e t r u e d i f f e r e n c e i n t h e e l e v a t io n o f
t w o p o i n t s i s a f f e c t e d b y t w o f a c t o r s- - t h e c u r v a t u r e o f t h e e a r t h ' s s u r f a c e a n d t h e
___________________________________________________________________________________.
A.
Effect of gravity on the earth's surface
B.
Refraction of light due to the earth's atmosphere
C.
Distance above the earth's surface where the two points are located
D.
Type of instrument used in observation between the two points
8.
With respect to the curvature of the earth, the effect of refraction is about _____________as
much and the ________________________ in sign.
A.
One-fourth, same
B.
One-fourth, opposite
C.
One eighth, opposite
D.
One-eighth, same
9.
A refraction line is a line_________________________________________________________.
A.
Parallel to the horizontal axis of the instrument being used
B.
Which conforms to the shape of the earth
C.
That is normally obstructed but becomes visible at night
D.
Perpendicular to the earth's surface
10.
The determining factor for the amount by which the line of sight must clear the ground is
the_________________________________________________________________________________.
A.
Amount of heat transferred to the atmosphere by the ground
B.
Height and number of obstructions in the line of sight
C.
Direction and velocity of the wind
D.
Viscosity or density of the vegetation directly below the line
2-49
EN0593
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