SURVEYING INSTRUMENTS AND MEASSURMENTS

• Galileo constructed a refracting telescope for astronomical

  observations.

  1609
• used in field mapping. It consists of a board attached to a tripod in

  such a way that it can be leveled or rotated to any desired direction.

  PLANE TABLE
• of transit is accredited to Young and Draper who worked

  independently from each other sometime in 1830.
• – a short auxiliary scale placed alongside the graduated scale of an

  instrument,

  VERNIER
• THE VERNIER WAS INVENTED BY PIERRE VERNIER, A FRENCHMAN IN WHAT YEAR?

  1631
• came into wide use during the 13th century for

  determining the direction of lines and in calculating angles between lines.

  COMPASS
• units of angular measurement are the degree, minute,

  and second.

  SEXAGESIMAL UNITS
• many countries in Europe and the Middle East use this unit where grad is the angular unit.

  centestimal units
• inaccuracies in measurements which occur because some aspect

  of a surveying operation is performed by the surveyor with carelessness,

  inattention, poor judgment, and improper execution.

  mistakes
• defined as the difference between the true value and a

  measured value of a quantity.

  error
• two types of errors:

  systematic error and accidental error
• type of error is one which will always have the same sign and magnitude as long as field conditions remain constant and unchanged.

  systematic error
• The occurrence of such errors are matters of chance as they are likely to be positive or negative,

  accidental error
• Indicates how close a given measurement is to the absolute or true

  value of the quantity


  accuracy
• refers to the degree of refinement and consistency with which

  any physical measurement is made.

  precision