# Latitude Definitions for Land Surveyors

latitude—1Angular distance measured on a meridian; now, distance, north or south, from the equator. The length of a degree of latitude varies on account of the flattened figure of the earth, being 68.704 statute miles at the equator, and 69.407 at the poles. 2 The orthographic projection of a course upon the meridian (either true or assumed) of a survey. It is equal to the length of the course multiplied by the cosine of the bearing. 3 The Perpendicular distance from a point of the bearing.

latitude—In surveying, the orthographic projection of a course upon the north-south axis of the survey. It is equal to the length of the course multiplied by the cosine of the bearing. It is east or positive and sometimes termed the easting, for a line whose azimuth or bearing is in the northeast or southeast quadrant; it is west or negative, and sometimes termed the westing, for a line whose azimuth or bearing is in the southwest or northwest quadrant.

latitude, astronomic—The angle between the plumb line and the plane of the celestial equator. Also defined as the angle between the plane of the horizon and the axis of rotation of the earth. Astronomic latitude is the latitude which results directly from observations of celestial bodies, uncorrected for deflection of the vertical (station error). Astronomic latitude applies only to positions on the earth and is reckoned from the astronomic equator (0°), north and south through 90°. See also coordinates, astronomic; longitude, astronomic.

latitude, geocentric—Latitude measured in the angle between the equatorial plane and a line connecting the center of the Earth with a point on its surface.

latitude, geodetic—The angle which the normal at a point on the ellipsoid makes with the plane of the geodetic equator. Geodetic latitudes are reckoned from the equator, but in the horizontal-control survey of the United States they are computed from the latitude of station Meades Ranch when using the North American datum of 1927. In recording a geodetic position, it is essential that the geodetic datum on which it is based be stated. A geodetic latitude differs from the corresponding astronomic latitude by the amount of the meridional component of the local deflection of the vertical (station error). Latitude as shown on topographic maps and navigators’ charts is geodetic latitude.

latitude, reduced—The angle, at the center of a sphere tangent to the rotational ellipsoid along the geodetic equator, between the equatorial plane and the radius to that point on the sphere where a straight line through the point of interest and perpendicular to the equatorial plane hits the sphere. When used in astronomy, geocentric latitude is meant. Also called “parametric latitude.”

latitude, variation of—A small periodic change in the astronomic latitude of points on the earth, caused by the variation of the pole.

latitude equation—See equation, latitude.

latitudinal curve—Easterly and westerly property lines adjusted to the same mean bearing from each monument to the next one in regular order, as distinguished from the long chord or great circle that would connect the initial and terminal points.

Source: NSPS “Definitions of Surveying and Related Terms“, used with permission.

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