Ge 10

Front 1

adjust the instrument, balance bs and fs distances

Back 1

to minimize error due to imperfect adjustment of the instrument

Front 2

careful focusing

Back 2

to eliminate error due to parallax

Front 3

balance Dbs by corresponding Dfs

Back 3

to eliminate error due to Earth's curvature

Front 4

keeping the LOS well above the ground(at least ~0.7m), taking bs and fs readings in quick succession

Back 4

in leveling of greater precision, error due to atmospheric refraction can be minimized by

Front 5

shield the instrument from the rays of sun

Back 5

to eliminate error due to variation in temperature

Front 6

compare the rod with a standard rod, apply correction analogous to a tape that is too short or too long

Back 6

to eliminate error because of rod not of standard length

Front 7

swinging the rod, use a rod level

Back 7

eliminating error due to rod not held plumb

Front 8

choose definite and stable points

Back 8

eliminating error due to faulty turning points

Front 9

choose stable locations, take bs and fs readings in quick succession preferably alternating order of sights

Back 9

eliminating error due to settlement of tripos or turning points

Front 10

proper choice of the length of sight

Back 10

reducing error due to inability of the observer to read the rod exactly or to set the target exactly on the LOS

Front 11

plumbline

Back 11

a vertical line used which is perpendicular to the tangent line of a level surface

Front 12

horizontal line

Back 12

a straight line which is tangent to a level surface

Front 13

vertical datum

Back 13

a surface to which elevations or depths are referred

Front 14

geoid

Back 14

a surface of constant potential energy (equipotential surface) that coincides with mean sea level over the oceans

Front 15

reference ellipsoid

Back 15

mathematical surface of reference

Front 16

orthometric heights

Back 16

geometrical distance between the Geoid and the point measured along the plumb line passing through the point

Front 17

ellipsoidal elevations

Back 17

elevation referred to the reference ellipsoid

Front 18

level surface

Back 18

surface every element of which is normal to the plumb line

Front 19

elevation

Back 19

vertical distance of a point above or below an arbitrarily assumed level surface or curved surface

Front 20

difference in elevation

Back 20

between two points is the vertical distance between the two level surfaces in which the points lie

Front 21

leveling

Back 21

the operation of measuring vertical distances, either directly or indirectly, to determine differences in elevation

Front 22

bench mark

Back 22

a definite point on an object, the elevation and location of which are known

Front 23

bench mark

Back 23

serves as point of reference for levels

Front 24

turning point

Back 24

an intervening point between two bench marks upon which point foresight and backsight rod readings are taken

Front 25

turning point

Back 25

its nature is usually indicated in the notes but location is not necessary

Front 26

backsight

Back 26

a rod reading taken on a point of known elevation

Front 27

backsight

Back 27

usually taken with the level sighting back along the line

Front 28

backsight

Back 28

sometimes called a plus sight

Front 29

backsight distance

Back 29

the horizontal distance from level to rod on a BS

Front 30

foresight

Back 30

a rod reading taken on a point of unknown elevation

Front 31

foresight

Back 31

sometimes called a minus sight

Front 32

foresight distance

Back 32

the horizontal distance from level to rod on a FS

Front 33

height of the instrument

Back 33

elevation of the line of sight of the telescope above the datum when the instrument is leveled

Front 34

dumpy, automatic, tilting, laser, digital, hand

Back 34

types of level

Front 35

dumpy level

Back 35

general purpose instrument and commonly referred as engineer's level

Front 36

Automatic level

Back 36

aka self-leveling

Front 37

automatic level

Back 37

allows the establishment of a horizontal line of sight by means of a compensator

Front 38

compensator

Back 38

a system of prisms and mirrors supported by wires as in a pendulum

Front 39

automatic level

Back 39

designed so that the LOS is horizontal when the telescope barrel is within ±10" of being horizontal

Front 40

automatic level

Back 40

leveled by the use of a circular spirit or bull's eye level and the compensator maintains a horizontal line of sight

Front 41

tilting level

Back 41

has a level bubble with a sensitivity of 10 in per 2 mm division and the images of the bubble ends are viewed through the eyepiece

Front 42

titling level

Back 42

equipped with coincidence bubbles used for precise leveling