First-order triangulation requires that sets of observations made on different stations (normally
16 positions of the horizontal circle) be performed___________________________________________.
Once a night for one night
Twice a night for two nights
Each of two nights, with a minimum of 2-hour separation between the two sets.
Each of two nights, with a minimum of 1-hour separation between the two sets.
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
Effect of gravity on the earth's surface
Distance above the earth's surface where the two points are located
Type of instrument used in observation between the two points
With respect to the curvature of the earth, the effect of refraction is about _____________as
much and the ________________________ in sign.
One eighth, opposite
A refraction line is a line_________________________________________________________.
Parallel to the horizontal axis of the instrument being used
Which conforms to the shape of the earth
That is normally obstructed but becomes visible at night
Perpendicular to the earth's surface
The determining factor for the amount by which the line of sight must clear the ground is
Amount of heat transferred to the atmosphere by the ground
Height and number of obstructions in the line of sight
Direction and velocity of the wind
Viscosity or density of the vegetation directly below the line