Transformation of conformal coordinates of type Lambert Conic from a global datum (ITRS) to a local datum (regional, National)
Grafarend, Erik and Francis Okeke
the past, in order to satisfy the surveying and mapping requirements of countries all over the earth. In most of these geodetic systems, the horizontal and vertical points are separated in location, monumentation, and measurement, and are referred to different datums. Local horizontal geodetic points have approximate or no heights, and benchmarks have very weak horizontal coordinates. In recent years, a growing trend toward the use of GPS observations and global mapping satellite systems have resulted in position based products in a world reference frame. There is therefore need in geodetic practice to transform coordinates referred to the local geodetic system to the global geodetic system and vice versa. Also a fundamental activity in land surveying is the integration of multiple sets of geodetic data, gathered in various ways, into a single consistent data set, that is into a common geodetic reference frame. Thus geodetic coordinate transformations find application in several instances, such as navigation, revision of older maps, cadastral surveying, GIS, industrial surveying, deformation studies, geo-exploration, etc. This paper treats the problem of how to transform from global datum, for instance from the International Terrestrial Reference system (ITRS) to a local datum, for instance of type regional or national, for the practical case of the Lambert projection of the sphere or the ellipsoid-of-revolution to the cone. We design the two projection constants 1 2 ( , ) n ϕ ϕ and 1 ( ) m ϕ for the Universal Lambert Conic project of the ellipsoid-of-revolution. The task to transform from a global datum with respect to the ellipsoid-of-revolution 2 , a b E to local datum with respect to the alternative ellipsoid-of-revolution 2 , a b E , without local ellipsoidal height, is solved by an extended numerical example.
Event: XXIII International FIG Congress : Shaping the change
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