Establishment of Geodetic Coordinate Systems - Geodesy: Introduction to Geodetic Datum and Geodetic Systems - page 336

Fig. 7.4 Principle for grid coordinate transformation
and certain mathematical models (e.g., the least curvature principle, least squares
collation, polynomial regression, and Bursa-Wolf model, etc.), we can compute the
differences between the longitude and latitude coordinates of the grid nodes at
certain distance intervals and establish the coordinate transformation grid model.
Then, all we need to do is use the quantities of coordinate transformation of the four
neighboring grid nodes of the points awaiting transformation to compute the
quantities of coordinate transformation based on the bilinear interpolation formula
(see Fig. 7.4 ). This approach is generally applied to the high accuracy transforma-
tion between the sheet lines of a topographic map and the square grids.
7.3 Classical Methods for Ellipsoid Orientation
7.3.1 Geodetic Origin Data and Ellipsoid Orientation
In classical geodesy, the ellipsoid orientation is meant to establish the geodetic
coordinate system, i.e., to determine, under certain conditions, the position of the
Earth ellipsoid with defined elements relative to the geoid, so as to obtain the
reference surface and the geodetic origin data for geodetic computations.
Ellipsoid orientation means: (1) to determine the position of the center of an
ellipsoid (abbreviated as positioning) and (2) to determine the direction of the
coordinate axes of the Cartesian coordinate system with its origin at the center of
the ellipsoid, i.e., to determine the pointing direction of the minor axis of an
ellipsoid and the plane of the initial geodetic meridian (abbreviated as orientation).
The origin (initial point) from which the geodetic coordinates of points in the
national horizontal geodetic control network are calculated is called the geodetic