Trimble Navigation Limited

Kenneth W McBride

John F Schipper

Mark Edward Nichols

Ian Timothy Viney

Richard Jackson

Arthur Taylor

A system for improving the accuracy of location coordinate determined in a survey of a chosen region. A grid of spaced apart points is imposed on the region, and a set of survey control points is provided. A &ldquo;near set&rdquo; of nearest survey control points is associated with each grid point, and the number of elements in this new set may vary with the grid point. Definition of a near set can vary from one grid point to the next. For each grid point, a transformation T from a first coordinate system to a second coordinate system is determined that minimizes a collective difference between coordinates of each survey control point in the near set and the corresponding coordinates of that survey control point under the transformation T. For one, two or three coordinates of each grid point, the difference(s) between the coordinate(s) of the grid point in the near set and the corresponding coordinate(s) of that grid point under the transformation T are computed. An interpolation function is determined that approximately matches the coordinate difference(s) at each grid point. The interpolation function provides a continuous datum-to-datum mapping between all points of the first and the second coordinate system. Determination of location of each survey point may use GPS, GLONASS, modified LEO or any other suitable location determination system.

Interpolation of survey coordinate differences

Methods for providing a representation of location coordinates for a collection of survey points with enhanced accuracy. An obliquely oriented cylindrical surface, rather than a tangent plane, is determined and used as the projection surface at or near a survey base point, with the angular orientation and radius of the cylinder being chosen to optimize the accuracy of the projection. A scale factor that corrects for distances of locations projected onto the cylindrical surface is optionally determined and applied. A three-dimensional transformation of survey location coordinates, optimized to provide a best fit for a selected set of fiducial survey locations, is determined that provides a correspondence between a globally determined height coordinate and a locally determined elevation coordinate.

Optimal survey map projection system

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 improving the accuracy of location coordinate determined in a survey of a chosen region, using a computer. A grid of spaced apart points is imposed on the region, and a set of survey control points is provided. A 'near set' of nearest survey control points is associated with each grid point. For each grid point, a transformation T from a first (global) datum and coordinate system to a second (local) datum and coordinate system is determined that minimizes a collective difference between coordinates of each survey control point in the near set and the corresponding coordinates of that survey control point under the transformation T. For one, two or three coordinates of each grid point, a difference .DELTA. between the coordinate(s) of the grid point in the near set and the corresponding coordinate(s) of that grid point under the transformation T is computed. An interpolation function is determined that approximately matches the coordinate(s) difference .DELTA. at each grid point. The interpolation function provides a continuous datum-to-datum mapping between all points of the first and the second coordinate systems. Determination of location of each survey point may use GPS, GLONASS, modified LEO, LORAN or any other suitable location determination system.

Method and apparatus for optimally transforming location coordinates from a global system GC1 of survey coordinates to a local system LC1 of coordinates in a location survey. Linear translation transformations T.sub.G1 and T.sub.L1 are determined that translate the GC1 coordinates and the LC1 coordinates new coordinates in coordinate systems LC1' and GC2 having a corresponding origin. A rotation transformation R(.phi.,.theta.), having a selected azimuthal rotation angle .phi. and a selected polar rotation angle .theta., that transforms the coordinate system LC1' into another coordinate system LC2 so that a coordinate plane or coordinate axes in LC2 are aligned with a coordinate plane or coordinate axes in GC2. An optimized invertible transformation T.sub.LC2,GC2 is found that minimizes a selected functional and carries GC2 into LC2. The optimal transformation of GC1 into LC1,

Optimization of survey coordinate transformations

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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Los Altos, CA, United States of America

Kenneth W McBride