MODULE 3- FOS

the general term applied to any of the various processes by which elevations of points or differences in elevation are determined.

 a curved line in a level surface all points of which are normal to the direction of gravity and equidistant from the center of the earth.

a curved surface which is at any point perpendicular to the direction of gravity or the plumb line. It is best represented by the surface of a large body of still water

It is a plane that is tangent a level surface at a particular point. also perpendicular to the plumb line at the same point

A straight line in a horizontal plane which is tangent to a level line at one point.

at any point sine parallel to the direction of gravity

an imaginary surface of the sea which is midway between high and low tides. This surface, which considered to be at zero elevation, conforms to the spheroidal shape of the earth and is perpendicular to direction of gravity at every point.

any convenient level surface coincident or Parallel with mean sea level to which elevations of a particular area are referred.

the vertical distance above or below mean se level or any other selected datum.

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

process of determining the difference in elevation between two or more points some distance apart. It requires a series of set ups of the instrument along a general route and, for each set up, a rod reading back to the point of known elevation are taken.

fixed point of reference whose elevation is either known or assumed. They may be permanent or temporary.

those which are established at intervals throughout the country by the Philippine Coast and Geodetic Surveys (PCGS) or the Bureau of Lands.

a reading taken on a rod held on a point of known or assumed elevation. It is measure of the vertical distance from the established line measure of sight to the point sighted, and is always the first rod reading taken after the instrument has been set up and levelled.

A reading taken on a rod held on a point whose elevation is to be determined.