Coordinate Systems, Datums and More

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2/4/2020

COORDINATE SYSTEMS, DATUMS AND MORE

Wisconsin Society of Land Surveyors Conference

Wisconsin Dells, 2020

PRESENTATION OUTLINE

A mostly non-technical look at survey coordinates Coordinate system components TYPE OF COORDINATES New U.S. datum strategies ELLIPSOIDS 2022 COORDINATES WGS84 U.S. SURVEY FOOT PROJECTIONS HTDP FALSE NORTHINGS & EASTINGS / ORIGINS DATUMS EPSG DATASET Other coordinate system considerations GEOIDS – GRACE PATCHWORK IS BECOMING GLOBAL EPOCHS ITRF TABLECLOTHS GEOCODING REGIONAL COORDINATES USER SOFTWARE – FIELD AND OFFICE HOUGHTEAM Realizing coordinates in the field NORTH CORS AND NETWORKS NETWORK DATUMS OPUS REPORTS PPP COORDINATE CALIBRATIONS SC104 COORDINATE TRANSFORMATION ANTENNAS

COORDINATE SYSTEM MECHANICS Coordinate System Components

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TYPES OF COORDINATES

• Number line • Plane • Polar • Cylindrical • Cartesian

GNSS use a hypotheoretical location as the centroid of an ellipsoidal model that best fits the earth’s shape.

ELLIPSOIDS

WGS84 (G1762) is the current ellipsoid being used by GPS • NAD83 coordinates are based on the GRS80 ellipsoid model • NAD27 coordinates are based on the Clark ellipsoid of 1866 • Trimble Business Center has at least 219 ellipsoid models in its database • Additional custom models can be created

WGS84

Semi-major axis 6378137 m | Semi-minor axis 6356752.31424518 m Flattening (1/f) 298.25722356301 | Eccentricity 0.0818191908426202

Year Realization (Epoch) Practical equivalent to… 1987 WGS1984 (Original) NAD83 (1986) 1994 WGS1984 (G730) ITRF91/92 1997 WGS1984(G873) ITRF94/96 2002 WGS1984 (G1150) ITRF00 2012 WGS1984 (G1674) ITRF08 2013 WGS1984 (G1762) Compares to ITRF08 within 1 cm RMS Source: https://rplstoday.com/community/gnss-geodesy/datums-2/paged/2/

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PROJECTIONS

Four types of projection distortions can occur • Distortions include: Shape, Size, Direction, Distance • Transverse Mercator generally used in North/South regions • Lambert Conformal generally used in East/West regions • Oblique Stereographic generally used in 1-step transformations The Universal Transverse Mercator system

MAP DISTORTION EXAMPLE

Abu Dhabi to Los Angeles

FALSE NORTHINGS & EASTINGS / ORIGINS

A look at Sauk County WISCRS projection • Transverse Mercator • Origin is near Blanchardville, WI • False Northing 0.017 Survey Foot • False Easting 609000.001 Survey Feet • Approximate Ground to Grid ratios • Low distortion • 1:500,000: Baraboo, Reedsburg, Wisconsin Dells, Lake Delton

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DATUMS

The NGS defines the official geodetic datums for all federal mapping activities in the U.S. and its territories as part of the National Spatial Reference System (NSRS)

• NAD27 NAD83 (NSRS2007) National Readjustment • NAD83 • NAVD88 • NAPGD2022 • Will be based on the IGSxx Time- Dependent Reference Frame

https://www.ngs.noaa.gov/NationalReadjustment/

EPSG DATASET

International Association of Oil & Gas Producers European Petroleum Survey Group

• Search the database http://www.epsg.org for "Sauk"

EPSG DATASET

International Association of Oil & Gas Producers European Petroleum Survey Group

• Search the database for "Sauk" • View the parameters for EPSG 7631

• Many organizations have suggested using the EPSG code for broadcasts from GNSS base stations to rovers. In this way, rovers have the possibility to be calibrated automatically into the active coordinate system regardless of brand and with homogeneity of the datum.

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GEOIDS – GRACE

Heights to Elevations

Earth Mass Center

WGS84 GEOID Ellipsoid

Ellipsoid Geoid Topographic Surface

GEOIDS – GRACE

Gravity Recovery And Climate Experiment

EPOCHS

Coordinates change over time • Reference Frames have Realizations

• NAD 83(CORS96) active control

• NAD 83(NSRS2007) passive control • Realizations have Epoch dates • NAD 83(2011) epoch 2010.00

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ITRF

International Terrestrial Reference Frame EPSG NAME EPOCH • Realization of the ITRS, International CODE Terrestrial Reference System* ITRF92 1988.0 4914 ITRF93 1988.0 4915 • ITRF and ITRS realizations are managed by ITRF94 1993.0 4916 the IERS, International Earth Rotation and ITRF96 1997.0 4917 Reference Systems Service* ITRF97 1997.0 4918 • Current global standard ITRF2000 1997.0 4919 ITRF2005 2000.0 4896 • New datums from the NGS will align with the ITRF2008 2005.0 5332 current ITRF** ITRF2014 2010.0 7789

*https://en.wikipedia.org/wiki/International_Terrestrial_Reference_System_and_Frame **https://www.ngs.noaa.gov/datums/index.shtml

REGIONAL COORDINATES

Many regions have localized coordinates • States including Wisconsin, Minnesota, Indiana and Iowa have created County based systems • Networks are using the RTCM Coordinate Transformation Messages to inform rovers about datum parameters • One-Step transformation to locally based Ground Control Points is still very common

GNSS APPLICATIONS AND INFRASTRUCTURE Realizing Coordinates in the Field

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CORS AND NETWORKS

Thousands of Continuously Operating Reference Stations around the world form networks of GNSS receivers

NETWORK DATUMS

Real-time network corrections define the datum at the rover • NAD83-2011 Epoch 2010.0 • Some networks are commercial enterprises • WRTN, ODOT, ORGN, TURN, INCORS, • Some networks are public NYSNet, WISCRS, IaRTN, TxDOT infrastructure with varying fee based • CRTN – NAD83-CSRS Epoch 2017.50 access • Some network datums are • TGRN – NAD83 (1995) constrained by historical, financial or • GDA2020 – ITRF2014 Epoch 2020.0 other considerations

OPUS REPORTS

OPUS Worldwide Post-Processing Service • Static RINEX files (*.YYo) can be uploaded to https://www.ngs.noaa.gov/OPUS/ to be processed into the NSRS (National Spatial Reference System) • If the submission includes a zero antenna height, OPUS will provide a warning/notice • Other file requirements include: Dual- frequency GPS between 15 minutes and 48 hours in duration

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OPUS REPORTS (2)

OPUS Worldwide Post-Processing Service • Information about the satellite orbits is in the Ephemeris file • There are three releases for a day's orbit file • Each release is slightly more accurate

https://www.ngs.noaa.gov/orbits/orbit_data.shtml 22

OPUS REPORTS (3)

OPUS Worldwide Post-Processing Service • RINEX NAV files contain constellation specific details: Satellite health, transmission time of message and fit interval • The correct antenna model and antenna height above the marker can be selected • The NGS manages a database of absolute geodetic antenna models to minimize azimuth and elevation dependent errors

OPUS REPORTS (4)

OPUS Worldwide Post-Processing Service • Overall (3D) RMS for this collection is calculated to be 0.017 meters • Solution is presented in two different reference frames as… • ECEF coordinates • Latitude and Longitude • Ellipsoidal Height • Geoidal Height and model that was used

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OPUS REPORTS (5)

OPUS Worldwide Post-Processing Service • Coordinates are also provided in global UTM and State Plane projected systems • Convergence angle (+/-) to the projected system's central meridian • Horizontal point scale – grid to ground • 3D Combined point scale – grid to ground • CORS data that was used to process the position is provided

PPP

Precise Point Positioning (State Space Representation) • The goal is to achieve under 4 centimeters of accuracy PPP-RTK anywhere in the world with PPP - State space PPP-Network - State space - Local/Regional - Observation no internet access - Global - Ambiguity State space - No ambiguity resolution - Local/Regional resolution - Cm accuracy - Ambiguity - Dm accuracy resolution - Cm accuracy

https://iotbusinessnews.com/2011/12/20/68809-u-blox-achieves- sub-meter-gps-accuracy-with-ppp-precise-point-positioning/

COORDINATE CALIBRATIONS

. Site Calibrations Turning global coordinates into Name Horz Vert North Error East Error Vert Error 1 Yes Yes 0.0000.0080.0050.0070.006 0.0000.0080.0060.0120.011 0.0000.0090.0080.007 survey points “The2 Yesproof Yes is 0.0000.0050.0080.009 in the 0.0000.0070.0090.010 dirt!” 0.0000.0100.0140.006 3 Yes Yes No 0.0060.0040.0050.008 0.0100.0090.0080.007 0.0000.0400.048-.--- 4 Yes Yes 0.0010.0030.005 0.0050.004 0.0030.004 5Phil Yes No Stevenson, Yes 0.033-.--- 0.076 -.---PLS0.009 0.011 Global LLH 2 points define rotation and scale 5 points provide Datum redundancy checks

3 points create a plane and Local LLH Project generate Hz residuals Area Map Projection Geoid 4 points generates Hz and Vt residuals Grid Y,X Z 1 point – North rotation, Scale = 1

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SC104 COORDINATE TRANSFORMATION

RTCM Special Committee 104 has developed messages that can automate the coordinate calibration process from the server side

Message Type Message Name 1021 Helmert/ Abridged MolodenskiTransformation Parameters 1022 Molodenski-BadekasTransformation Parameters 1023 Residuals, Ellipsoidal Grid Representation 1024 Residuals, Plane Grid Representation Projection Parameters, Projection Types other than Lambert 1025 Conic Conformal (2 SP) and Oblique Mercator Projection Parameters, Projection Type LCC2SP (Lambert 1026 Conic Conformal (2 SP)) 1027 Projection Parameters, Projection Type OM (Oblique Mercator) 1028 (Reserved for Global to Plate-Fixed Transformation)

ANTENNA

GNSS antennas vary Magellan 111406 L1 Offset – 6.01 cm (2.37”) • PCV = Phase Center Variation • ARP = Antenna Reference Point Spectra Epoch 35 L1 Offset – 9.97 cm (3.93”) 90° 90°

Phase Center Phase Center

0° 0° Spectra SP60 Antenna Reference Point Antenna Reference Point L1 Offset – 5.05 cm (1.99”) Phase Meter Phase Meter +π +π

0.f λ 0.f λ -π -π Elevation Elevation Ashtech 111661 (Imaginary) Ideal Antenna Real Antenna Pattern L1 Offset – 5.72 cm (2.25”)

CHANGES ARE COMING FROM THE NGS New U.S. Datum Strategies

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2022 COORDINATES

Goodbye NAD83, Hello NATRF2022 • Active Control replaces Passive Control • Time dependent coordinates aligned within a global framework HELLO Goodbye NAVD88, Hello NAPGD2022

• Geopotential Coordinates (Vertical) Goodbye HTDP, Hello IFVM GOODBYE

• The method for calculating tectonic motion will be changing

2022 COORDINATES

Providing geodetic control can be... • Global, plate-independent reference frames, such as the ITRF which embraces time dependency as part of geodetic control or… • “Plate Fixed Frames” such as NAD 83, which attempt to “affix” a coordinate frame to one tectonic plate so as to maintain unchanged coordinates on that plate. This approach assumes rigidity of the tectonic plate

2022 COORDINATES

The new NSRS will have four tectonic regions • North American, Pacific, Caribbean & Mariana • Motion in these regions will be primarily defined by velocities and a "Euler-pole" • In non-rigid areas of a plate, IFVM's will be utilized • Ideal frames (ITRF) do not meet the needs of land surveyors • Plate-fixed frames do not meet the needs of academia, scientific interests and others

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2022 COORDINATES

To combine ITRF and plate-fixed frames, two conditions will be met • Condition 1: The coordinates of all points in a plate-fixed frame should remain constant through time, provided all of those points rotate about the Euler Pole with the same angular velocity and otherwise have no other motions • Condition 2: The coordinates of all points in a plate-fixed frame are identical to their coordinates in the ideal frame at some initial chosen

epoch t0

U.S. SURVEY FOOT

What is a foot? • U.S. Survey foot = 0.3048006096 meters Exactly12003937 meters • International foot = 0.3048 meters A difference of approximately 2 PPM What is a meter? • Original definition as 1/10,000,000 of the distance from the equator to North Pole • Today's definition is the distance light travels in 1/299,792,458 of a second

U.S. SURVEY FOOT

Federal Register / Vol. 84 No. 201 / Thursday, October 17, 2019 / Notices DEPARTMENT OF COMMERCE National Institute of Standards and Technology Duluth Deprecation of the United States (U.S.) Survey Foot AGENCY: The National Institute of Standards and Technology and the National Geodetic Survey (NGS), National Ocean Service (NOS), National Oceanic and Atmospheric Administration (NOAA), Department of Commerce (DOC).

SUMMARY: The National Institute of Standards and Technology (NIST) and the National Geodetic Survey (NGS), National Ocean Service (NOS), National Oceanic and Atmospheric Dubuque Administration (NOAA), are taking collaborative action to provide national uniformity in the measurement of length. This notice announces a decision to deprecate the use of the Grid Distance: Dubuque to Duluth ‘‘U.S. survey foot’’ on December 31, 2022. After that date, the ‘‘U.S. survey foot’’ will be superseded by the ‘‘foot’’ (formerly Intl Foot: 1606274.845 known as the ‘‘international foot’’), which is already in use US SFT: 1606271.632 throughout the U.S. 3.213

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U.S. SURVEY FOOT

Rationale for the transition • Reduce confusion in surveying and mapping where computing accurate coordinates over large distances are commonly required • The modernization of the National Spatial Reference System (NSRS) in 2022 is the perfect time to move the United States toward a single, uniform definition of the foot • Measurement unit uniformity is only possible when a single measurement unit definition is used for a specific application (e.g., land surveying and gas stations)

U.S. SURVEY FOOT

What are the implications of this retirement? • Terms that have been based on survey feet will now be referenced to international feet – chain, furlong, fathom and acre • Surveyors will become expert with the conversion • GIS and other mapping products will need to be updated • Eventually… ease of use • Legislation will slowly adapt • Tape measures will not be impacted

HTDP

Horizontal Time Dependent Positioning Software • The primary mission of • The new approach will be the use of IFVM the NGS is to manage to describe motions through time* the NSRS and its control • HTDP software does not contribute to this mission • HTDP drains resource

2020 63 cm in • Original requests for 20 years HTDP came from universities 2000

* The exact nature of this IFVM tool remains to be determined 39

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OTHER COORDINATE SYSTEM CONSIDERATIONS Miscellany

PATCHWORK IS BECOMING GLOBAL

World maps 25 years and older were mosaics • GNSS, VLBI, GRACE and other technologies combined have allowed the earth to be mapped from a single database

TABLECLOTHS

A table can have many tablecloths • Imagine that the table is your GNSS data collected by an RTK rover • The tablecloth represents your projection • GNSS data can always be re- projected into different systems in the same way a table can have a different tablecloth

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GEOCODING

Geocodes – the key to e-Government readiness (October 2019 issue of Coordinates eZine: https://mycoordinates.org/pdf/oct19.pdf)

• A basic requirement for effective spatial enablement is the availability of geocodes. • Geocodes derived from cadastral and land administration systems are ideal because the source databases….have integrity, are authoritative, are kept up to date and are linked to a map base and reference system

USER SOFTWARE – FIELD AND OFFICE

Will your software be ready... • Convert previous jobs, projects and maps to the "foot" • Does your software recognize the difference? • How will points be recognized as being from the old datum or new datum? The coordinates will be quite close

HOUGHTEAM

The untold story of the secret mission to seize Nazi map data https://www.smithsonianmag.com/history/untold-story-secret-mission-seize-nazi-map-data-180973317/

• Team of 19 carefully selected individuals • In Wiesbaden, Houghteam found of cache of survey books containing thousands of survey points in Germany • In Friedrichroda and Waltershausen, Houghteam found the entire civilian survey dataset for all of the German territory • In Saalfeld, the Houghteam found the central map and geodetic library for the German army • Houghteam provided vital information to allied forces • Houghteam data continued to help the U.S. during the cold war

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NORTH

True Geodetic North and Celestial or Astronomical North

• Celestial north varies slightly

from geodetic true north due to

local gravity perturbations that

may not point at the exact

rotational axis of the earth

NORTH

Magnetic North and Grid North

NORTH

North of Convenience

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THE END Thank You

Joe Sass | Channel Development Manager | Spectra Geospatial, A Trimble Company 49