LEVELING RODS

• LEVELING RODS -A graduated rod used for measuring the vertical distance between the line of sight through a leveling instrument and the point whose elevation is either required or known. -3-4 meters
• Classification of leveling rods:

  • SELF-READING ROD

  • TARGET ROD
• SELF-READING ROD -most commonly used type of leveling rod. It can be read directly by the instrumentman through the telescope by nothing the apparent intersection of the horizontal hair on the rodm
• TARGET ROD - this type of rod has a sliding target which is set and read by a Rodman at the position selected by the instrumentman.
• PHILADELPHIA ROD -it is combination of self reading and target rod and is commonly used rod. It is made up of two sections in which the rear section slides over the front section
• CHICAGO ROD -It comes in three sliding section, and usually extends to either three or four meters. This is more suitable for longer distances. Similar to Philadelphia rod except that it is wider
• ROD RIBBONS -improvised type of rod. The graduations are marked in canvass or metal strips which are attached to a long piece of selected lumber by staples
• PRECISE ROD - A form of rod ribbon which uses a graduated invar strip permanently fastened to a four-meter wooden or metal frame
• GEODETIC ROD -similar to precise rod, except that a nilvar strip is used instead of invar.
• NILVAR -is an alloy with a very low coefficient of linear expansion
• TAPE ROD -seldomly used rod and also known as automatic rod. It is used advantageously when numerous elevations are to be determined from a single set up of the leveling instrument.
• ROD LEVEL -Device used for fast and correct plumbing of a leveling rod.
• TARGET -A small device attached to the rod when extremely long sights make direct reading of the rod difficult or impossible
• TELESCOPE -is a metal tube containing a system of lenses which are used to fix the direction of the line of sight and in magnifying the apparent size of the objects in its field of view
• Jan Lippershey -he invented the telescope
• Johannes Kepler - suggested how the telescope could be employed for use in surveying instruments
• ESSENTIAL PARTS OF TELESCOPE:

  • OBJECTIVE LENS

  • EYEPIECE

  • CROSS HAIRS
• OBJECTIVE LENS -compound lens composed of crown and flint glass mounted in the objective end of the telescope and has its optical axis concentric with the tube axis

  -allow the light rays to enter the telescope and form an image of object sighted within its field of view
• EYEPIECE -form of microscope containing either two or four lenses and is used to enlarge altogether the image and the cross hairs
• CROSS HAIRS -pair of lines which are perpendicular to each other and are used to define the instruments line of sight
• MAGNIFICATION -ratio of the apparent size of an object viewed through telescope to its size as seen by the unaided eye from the same distance
• LEVEL VIALS -sealed graduated glass tube containing some amount of liquid and small air bubble. It is used to determine the direction of gravity
• COINCIDE BUBBLES -type of bubble which is used on most modern and precise instruments such as the tilting and automatic levels.
• TRIPOD -serves as a base to prevent movement of the instrument after it is set-up.
• TYPES OF TRIPOD:

  • FIXED-LEG TRIPOD

  • EXTENSION TRIPOD
• FIXED-LEG TRIPOD -a tripod made of fixed solid piece of wood or metal. It is more rigid and makes it possible to keep the line of sight higher above the ground.
• EXTENSION TRIPOD -A tripod with a sliding or adjustable leg. This suited for rugged terrain set ups where legs need to be adjusted to fit the configuration of the ground.
• At each end of a tripod is attached as pointed piece or metal called SHOE
• Rods Named after Cities or States:

  • Philadelphia

  • Chicago

  • Detroit • Boston

  • New York

  • Florida

  • Troy

  • San Francisco