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Before GPS: Determining a Benchmark using Celestial MethodsPE & PLS

Roy Timpe, PE

GPS would not exist had not astronomers and surveyors first accurately characterized the globe with a coordinate system of latitude and longitude. Prior to GPS the only way to survey a location was to reference it relative to another known benchmark (or control point.) How was the first benchmark referenced? The answer is the stars. If a survey had to be made of a remote island or other region where referencing benchmarks was impractical, a surveyor had to consult the stars. This course will discuss using celestial methods to determine latitude and longitude. The course intends to give the reader an appreciation of these methods. At the end of the course the reader will understand how to survey a point using several measurements of the sun over time to get accuracy to better than two thousand yards. The theory behind celestial measurements is explained in detail along with a discussion of the sources of error. GPS theory of operation, and sources of error are discussed as well.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

* If you are a registered professional land surveyor in Florida, Missouri, New Jersey, New York, Tennessee, Texas or Vermont, you need to take the approved courses for that specific state under the course category "Surveying & Mapping".

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NY PE & PLS: You must choose courses that are technical in nature or related to matters of laws and ethics contributing to the health and welfare of the public. NY Board does not accept courses related to office management, risk management, leadership, marketing, accounting, financial planning, real estate, and basic CAD. Specific course topics that are on the borderline and are not acceptable by the NY Board have been noted under the course description on our website.