Course Description
This second course on the series on State Plane Coordinate Systems covers just a bit of material from the previous course, reviewing the idea of projections and how they work in the case of the Transverse Mercator and Lambert Conformal systems. The course then moves on to discuss how measurements on the topographic surface of the earth are first reduced to sea level (the geodetic distance), before projecting them onto the developable surface appropriate for each type of system. How the distortions in east-west lines and north-south lines once they are projected to the grid are discussed. Then, the 1983 system’s overall points are covered, where necessary, contrasting them with those of the 1927 system. How the 1983 system deals with shapes of states that require use of more than one projection are briefly discussed. Also discussed is the importance of understanding which system of linear units (meters, feet or U.S. Survey feet) has been legislatively adopted, and making the appropriate conversions. When state plane coordinate system values are used, even the 2 PPM difference between the International foot and the U.S. Survey foot is considerable. The course again covers the matter of distortion for each type of projection.
Objectives
- Important concepts from the previous course in the series are reviewed.
- The concept of moving a distance at the ground to the ellipsoid and then to the grid is discussed.
- Distortions that occur with each type of projection are introduced.
- How the 1983 system differs from the 1927 system is discussed.
- How zones vary with shape of the area to be covered is presented.
