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3-D Global Spatial Data Model Continuing Education Seminar Instructor: Earl F. Burkholder, PS, PE Sponsored by the ASCE Geomatics Division Richard Popp, PE – Chair 1:00 to 5:00 p.m., March 21, 2011 The Woodlands Waterway Marriott At SPAR 2011 – Houston, Texas

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico The Global Spatial Data Model (GSDM) provides a way to organize concepts for a better understanding of 3-D spatial data. The GSDM does not take anything away from what you already know but adds valuable insight into the relationships between coordinate systems. The GSDM will enable you to become more comfortable with routine use of 3-D data.

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Welcome, Introductions, and Overview Big picture reason for GSDM – single origin History and background – with Q and A Three coordinate systems: 1. Geodetic, traditional latitude/longitude 2. Geocentric, Earth-centered Earth-fixed 3. Local, flat earth Basic elements and conventions

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Types of and generating spatial data Models for spatial data manipulation 1. Functional Model, equations and geometry - Flat earth includes horizontal & vertical - Geodetic latitude/longitude/height - Geocentric, earth-centered earth-fixed 2. Stochastic Model, standard deviations - Spatial data accuracy - Error propagation Tie into use of real-time GPS networks (RTN)

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Resources and References Web site – 1. Articles 2. Overheads Book – The 3-D Global Spatial Data Model 1. Published by CRC Press Google Global Spatial Data ModelGlobal Spatial Data Model National Academy of Public Administration GPS: Charting the Future GIS for the 21 st Century

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico This is where we jump into the nitty- gritty. Any questions before we get started? What is the future of 3-D? Exciting! Reasons for attending? Certificates and continuing education Registration boards Protecting the public We do it because it is the thing to do!

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Big Picture Justifications: - With electronic revolution spatial data are: 1. Digital 2. Three-dimensional - Measurement systems collect 3-D data - Spatial data are stored in computer files - Many disciplines work with spatial data - Think globally, work locally - Spatial data accuracy is critical

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico History is ‘recent’ but old: Computers and electronic storage foster use of an integrated 3-D data base. Many applications still treat horizontal & vertical separately. It is our view of the world. René Descartes (1596 – 1650) formalized geometry, Discourse on the Method, Global 3-D control polyhedron was proposed by Burns in GPS made it practical.

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Background Flat earth and 2D maps – this is our history. Implications of curved earth (How do you know the earth is not flat?) Map projections: - Portray curved earth on a flat surface - Strictly 2-D mathematical model The Digital Revolution includes: - Computers, electronics, and gadgets. - Photogrammetry, GPS/GNSS, Scanning

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Where is origin for your coordinate system? - Local/assumed (not much ‘big picture’ use) - State plane, northings & eastings, unique? - Geodetic latitude/longitude, curvilinear - Geocentric rectangular center of Earth Elevation, origin is geoid (or mean sea level). Non-compatible origins is a huge problem!

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Three different coordinate systems: Local, many spatial data users. - x & y or north & east flat-earth values - Is origin well defined or monumented? - Elevation is ‘up’ - Vertical origin is mean sea level (geoid).

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Geodetic & geographic (ellipsoidal/spherical) - Computations on ellipsoid or sphere. - Latitude and longitude curvilinear values. - Position in degrees-minutes-seconds. - Equations are cumbersome and complex. - Third dimension is ellipsoid height or altitude. Is that elevation?

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Geocentric earth-centered earth-fixed (ECEF) - Rectangular coordinates in meters. - Origin at earth’s center of mass. - X and Y are in plane of equator. - Z axis is parallel to spin axis of earth. (there is no “up” in ECEF!) - Uses rules of solid geometry - Vector algebra & matrices easy & efficient - Rotation matrix makes ECEF practical! - Eastings/northings same as lat’s and dep’s

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Basic Elements and Conventions: 2-D x & y, plane Euclidean geometry 3-D condo surveys, plan & profile, topo maps Geodetic latitude, longitude, height Geocentric earth-centered earth-fixed (ECEF) (Rules of solid geometry & vector algebra) Units for angles and distances Conventions – right handed rule e/n/u

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Types of spatial data Absolute with respect to coordinate system (Often used by GIS for spatial data analysis) Relative with respect to another point (Often used by surveyors & mappers etc) Reference frames and datums (Spatial data accuracy is an important issue whether using absolute or relative data.)

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico How are spatial data generated? Measurement of physical quantities. Direct vs indirect measurements Pacing, tape, total station, leveling, GPS, photogrammetry, remote sensing ‘Italian job’ How are spatial data components computed? Context determined by: - Orientation; azimuth, gravity, other. - Scale; units – chains, feet, meters, other

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Models for spatial data manipulation: Conventional 1-D and 2-D - COGO. Evolution of 3-D data Analog to digital Error propagation – calculus rates of change Standards and specifications: - ACSM/ALTA: 0.07 feet + 50 ppm - Geodetic (FGDC 1998)(FGDC 1998) - Other (many)

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Functional Model Equations and geometry 3-D integrated data base (stores it all) Working from whole to part - hiearchy Coordinate systems Datums Networks Rotation matrix provides flat earth 2-D COGO is a sub-set of 3-D X/Y/Z.

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Stochastic Model - Spatial data accuracy: Standard deviation With respect to what? How good is good enough? Error propagation Σ = J Σ J t (Matrix form) Confidence levels 95% at 2 sigma level is standard practice. OPUS – how good is it?

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Tie into Use of Real-Time Networks The GSDM is equally applicable to: - Any 3-D datum (but only 1 at a time), i.e.: 1. ITRF 2. WGS NAD 83 Any brand of GPS equipment: - Vendors are fully aware of ECEF values - Equations for GSDM are “open”

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Additional Information on the 3-D GSDM Defining document for the GSDM ION presentation containing equations etc. Spatial Data Accuracy Description for surveyors

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3-D Global Spatial Data Model (GSDM) Seminar Presented by: Earl F. Burkholder, PS, PE – Las Cruces, New Mexico Example GSDM Projects Geodetic control using static observations Leveling using GPS and geoid modeling Property (boundary) survey using the GSDM

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