Describes The Different Types Of Levels Used In Surveying (Essay Sample)

Types of level
1 Dumpy level
2 Tilting
3 Automatic level
4 Digital auto level
Dumpy level
These are more basic levels often used in construction work. The telescope is rigidly attached to a single bubble and the assembly is adjusted either by means of a screwed ball-joint or by foot screws which are adjusted first in one direction then at 90.
Tilting level
Equipped with circular spirit level for rough leveling which telescope is pointed to the rod. The telescope is precisely leveled by tilting screw which raise or lower eyepiece end of telescope until tube level is leveled. Tube level is viewed through separate eyepiece lens or telescopes its self. With 3 screws leveling the base and screws can also change elevation of line of sight.
Automatic level
Employs gravity referenced prism or mirror compensator to automatically orient the line of sight (line of collimation). The instrument is quickly leveled using circular spirit level. A compensator maintains horizontal LOS even if telescope is slightly titled using 3 or 4 screws leveling the base 2 and 3 Screws can change elevation of line of sight
Digital auto level
Uses electronic image processing for determining height and distance. Electronic mode with rod face graduated in bar code Compare image with the whole rod image. Auto determination of height & dist and recorded
Adjustment
To check the accuracy of a carpenter's type level, a perfectly horizontal surface is not needed. The level is placed on a flat and roughly level surface and the reading on the bubble tube is noted. This reading indicates to what extent the surface is parallel to the horizontal plane, according to the level, which at this stage is of unknown accuracy. The spirit level is then rotated through 180 degrees in the horizontal plane, and another reading is noted. If the level is accurate,
it will indicate the same orientation with respect to the horizontal plane. A difference implies that the level is inaccurate.
Adjustment of the spirit level is performed by successively rotating the level and moving the bubble tube within its housing to take up roughly half of the discrepancy, until the magnitude of the reading remains constant when the level is flipped.
A similar procedure is applied to more sophisticated instruments such as a surveyor's level or a theodolite and is a matter of course each time the instrument is set up. In this latter case, the plane of rotation of the instrument is leveled, along with the spirit level. This is done in two horizontal perpendicular directions.
Leveling procedures
A typical procedure is to set up the instrument within 100 meters (110 yards) of a point of known or assumed elevation. A rod or staff is held vertical on that point and the instrument is used manually or automatically to read the rod scale. This gives the height of the instrument above the starting (back sight) point and allows the height of the instrument (H.I.) above the datum to be computed.
The rod is then held on an unknown point and a reading is taken in the same manner, allowing the elevation of the new (foresight) point to be computed. The procedure is repeated until the destination point is reached. It is usual practice to ...