Trimble Navigation Limited

Richard Jackson

John F Schipper

Mark Edward Nichols

Ian Timothy Viney

Kenneth W McBride

Arthur Taylor

Michael E Jackson

Method and apparatus for enhancing the accuracy of the elevation coordinate in a survey that uses GPS survey measurements to determine location coordinates for a plurality of survey locations. An optimal locally-best-fitting plane is combined with a geoid model that represents a local region of the Earth, in order to decrease the inaccuracy associated with an elevation coordinate in the survey to a fraction of a decimeter.

Real time integration of a geoid model into surveying activities

A system for selecting an optimal transformation T(G2;G1) between a first ellipsoid E1 (e.g., WGS 84) in a first global coordinate system G1, relative to which the survey measurements are made, and a second ellipsoid E2 (e.g., NAD 27) in a second global coordinate system G2. Location coordinates (x'.sub.m,2,y'.sub.m,2,z'.sub.m,2) for M previously-surveyed locations, numbered m=1, . . . , M (M&gt;1) in the second system, and location coordinates (x'.sub.n,1,y'.sub.n,1,z'.sub.n,1) for N presently-surveyed locations, numbered n=1, . . . , N (M&lt;N), in the first system are provided, where M presently-surveyed locations coincide with the M previously-surveyed locations. The transformation is chose.sub.n so that the images of previously-surveyed locations in the first system under the transformation T are as close as possible to the corresponding [previously-surveyed] locations in the second system. Give.sub.n an ellipsoid and a selected survey plane .tau.0 that is tangent to the ellipsoid, a set of selected locations can be surveyed with reference to the ellipsoid, and the location coordinates of each such surveyed location can be mapped into a corresponding 'survey location,' defined by reference to a local coordinate system that uses the survey plane .tau.0 as its base. These transformations and projections are determined and optimized in real time, at the time a surveyor is measuring the presently-surveyed locations in the field. The instruments used for surveying may be part of a location determination system, such as GPS, GLONASS or Loran.

Survey coordinate transformation optimization

A system for selecting an optimal transformation T(G2;G1) between a first ellipsoid E1 (e.g., WGS 84) in a first global coordinate system G1, relative to which the survey measurements are made, and a second ellipsoid E2 in a second global coordinate system G2. A set of location coordinates (x'.sub.m,2, y'.sub.m,2,z'.sub.m,2) for M previously-surveyed locations, numbered m=1, . . . , M, and a set of location coordinates (x'.sub.n,1, y'.sub.n,1,z'.sub.n,1) for N presently-surveyed locations, numbered n=1, . . . , N (M.ltoreq.N) are provided, where the first M presently-surveyed locations coincide with the M previously-surveyed locations. The transformation is chosen so that the images of the location coordinates (x'.sub.n,1,y'.sub.n,1, z'.sub.n,1) for n=1, . . . , M under T(G2;G1) are as close as possible to the corresponding location coordinates (x'.sub.m,2,y'.sub.m,2, z'.sub.m,2) for m=1, . . . , M. Given an ellipsoid and a selected survey plane .tau.0 that is tangent to the ellipsoid at a selected location, a set of selected locations can be surveyed with reference to the ellipsoid, and the location coordinates of each such surveyed location can be mapped into a corresponding 'survey location,' defined by reference to a local coordinate system that uses the survey plane .tau.0 as its base. These transformations and projections are determined and optimized in real time, while a surveyor is measuring the presently-surveyed locations in the field. The instruments used for surveying may be part of a location determination system, such as a Global Positioning System, a Global Orbiting Navigational Satellite System or Loran.

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San Francisco, CA, United States of America

Richard Jackson