Preparing Minnesota’s Coordinate Systems for 2022 · Transverse Mercator Oblique Mercator...
Transcript of Preparing Minnesota’s Coordinate Systems for 2022 · Transverse Mercator Oblique Mercator...
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Preparing Minnesota’s Coordinate Systems for 2022
Geoff Bitner, LSMnDOT/NGS State Geodetic Coordinator
67th MSPS Annual MeetingFebruary 15, 2019
Collect in Coordinates
Compute in Coordinates
Construct in Coordinates
Grid Coordinates are Everywhere
Coordinate Systems Will Need Updating
New datum in 2022 (Reference Frame)
• Expect coordinate shifts of ≈ 1.0m‐1.5m
• Expect elevation shifts of ≈ ‐0.75m
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Purpose of Today’s Presentation
• Cover some coordinate system basics
• Look at available methods and options
• Review a brief history of coordinate systems in MN
• Look at the future of the County Coordinate system
• Discuss State Plane for 2022
Grid Coordinate System
• A rectangular (Cartesian) system based on straight line distances which approximate measurements upon the surface of the Earth
• An ordered pair of perpendicular axis
Source: By K. Bolino - Made by K. Bolino (Kbolino), based upon earlier versions., Public Domain, https://commons.wikimedia.org/w/index.php?curid=869195
Issues with Grid Systems
• Projections or flattening the sphere
• Consider the size and shape of the project area
• Distortions or dealing with scale
• Consider the effects of distance and elevation
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Three Common Projections
◦ Lambert Conic
◦ Transverse Mercator
◦ Oblique Mercator
Three Common Projections
◦ Lambert Conic
◦ Transverse Mercator
◦ Oblique Mercator
Source: The Minnesota County Coordinate System: a handbook for users; Whitehorn, Kenneth; St. Cloud, MN, 1997, Fig. 4
Source: Oregon Coordinate Reference System, Handbook and User Guide, available at ftp://ftp.odot.state.or.us/ORGN/Documents/ocrs_handbook_user_guide.pdf
Three Common Projections
◦ Lambert Conic
◦ Transverse Mercator
◦ Oblique Mercator
Properties of a Lambert Conic
• Think of a cone placed over a sphere
• Good for areas long in the east/west direction
• May intersect the ellipsoid along two parallels (secant) or one (tangent)
• Used in State Plane and many MN County coordinates
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Three Common Projections
◦ Lambert Conic
◦ Transverse Mercator
◦ Oblique Mercator
Source: The Minnesota County Coordinate System: a handbook for users; Whitehorn, Kenneth; St. Cloud, MN, 1997, Fig 5.
Source: Oregon Coordinate Reference System, Handbook and User Guide, available at ftp://ftp.odot.state.or.us/ORGN/Documents/ocrs_handbook_user_guide.pdf
Three Common Projections
◦ Lambert Conic
◦ Transverse Mercator
◦ Oblique Mercator
Properties of Transverse Mercator
• Think of a cylinder placed over a sphere, parallel with the equator
• Good for areas long in the north/south direction
• Best known for its use in the Universal Transverse Mercator (UTM) grid system
• Also used in several MN County coordinates
Three Common Projections
◦ Lambert Conic
◦ Transverse Mercator
◦ Oblique Mercator
Source: The Minnesota County Coordinate System: a handbook for users; Whitehorn, Kenneth; St. Cloud, MN, 1997, Fig. 6
Source: Oregon Coordinate Reference System, Handbook and User Guide, available at ftp://ftp.odot.state.or.us/ORGN/Documents/ocrs_handbook_user_guide.pdf
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Three Common Projections
◦ Lambert Conic
◦ Transverse Mercator
◦ Oblique Mercator
Properties of Oblique Mercator
• Think of a cylinder placed over a sphere and rotated for best fit
• Best known in Minnesota for its use along the North Shore of Lake Superior
• Can be difficult to model in software and field controllers
Source: The Minnesota County Coordinate System: a handbook for users; Whitehorn, Kenneth; St. Cloud, MN, 1997, Fig. 6
Source: Oregon Coordinate Reference System, Handbook and User Guide, available at ftp://ftp.odot.state.or.us/ORGN/Documents/ocrs_handbook_user_guide.pdf
Issues with Grid Systems
• Projections or flattening the sphere
• Consider the size and shape of the project area
• Distortions or dealing with scale
• Consider the effects of distance and elevation
Two Types of Distortion
Linear
• Often thought of as a ratio of distortion related to distance
+/‐ 20 ppm (mm/km)+/‐ 0.11 ft/mile1:50,000
• Can be positive or negative
Angular
• Known as the convergence angle for conformal projections
• Or, the difference between grid north and geodetic north
• The convergence angle increases with distance from the central meridian
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Linear Distortion
• Negative DistortionGrid shorter than Ground
• Positive DistortionGrid longer than Ground
Source: Understanding the State Plane Coordinate System, available at http://www.ngs.noaa.gov/PUBS_LIB/UnderstandingSPC.pdf
Linear Distortion due to Earth Curvature
Source: Oregon Coordinate Reference System, Handbook and User Guide, available at ftp://ftp.odot.state.or.us/ORGN/Documents/ocrs_handbook_user_guide.pdf
Linear Distortion due to Ground Ht vs. Plane Ht
Source: Oregon Coordinate Reference System, Handbook and User Guide, available at ftp://ftp.odot.state.or.us/ORGN/Documents/ocrs_handbook_user_guide.pdf
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Distortion Example Between Grid Systems
Earth SurfaceEllipsoid
Ellipsoid Semi‐major Semi‐minor
GRS80 6,378,137.0 6,356,752.3141
Crow Wing 6,378,546.96 6,357,160.896
Distortion Example Between Grid Systems
Ellipsoid Semi‐major Semi‐minor
GRS80 6,378,137.0 6,356,752.3141
Crow Wing 6,378,546.96 6,357,160.896
Expands ellipsoid height by ≈ 410m
JONES 2Ellip Ht. 370.5m
RABBIT RESETEllip. Ht. 397.5m
Distortion Example Between Grid Systems
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Expands ellipsoid height by 409.957m
JONES 2RABBIT RESET
UTM15
57,726.63’ State Plane
14.64ft 57,741.27’ Crow Wing Cnty
22.27ft 7.63ft 57,748.90’
Distortion Example Between Grid Systems
Purpose of Today’s Presentation
• Cover some coordinate system basics
• Look at available methods and options
• Review a brief history of coordinate systems in MN
• Look at the future of the County Coordinate system
• Discuss State Plane for 2022
Grid System Options
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Grid System Options
Use an Existing Coordinate System
1. State Plane or UTM
Create a Coordinate System to Minimize Distortion
1. Modify an existing system – State Plane/UTM
2. Modify the ellipsoid – Effectively altering the datum
3. Develop a modern Low Distortion Projection system such as those in Iowa, Kansas, Indiana, or Wisconsin
Popular Coordinate Systems in MN
Universal Transverse Mercator or UTM
In MN – UTM15 E “E” is for Extended
• Developed in the 1940s• Zone widths, 6° Longitude• Scale less than 1:2,500
≈½ per mile• Great for GIS and large scale planning
Source: http://www.history.noaa.gov/stories_tales/geod1.html
Popular Coordinate Systems in MN
State Plane Coordinate System – (not so popular?)
• C&GS for civilian use• Developed in 1930s• Defined by state/county• Three zones in MN based on Lambert Conic prj.
• Distortion ≈ 1:10,500
Source: https://geodesy.noaa.gov/SPCS/index.shtml
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Popular Coordinate Systems in MN
UTM andState Plane
Earth SurfaceEllipsoid
Justification for Minimizing Distortion
• Eliminates the need to scale coordinates and reduces the chance for conversion error
• Measurements are close to being 1‐to‐1, i.e.,
1 foot in the field = 1 foot in the office
• Angles in the field match angles in the office
• Modern systems can be developed for easy use in software, standardized procedures, and universal acceptance
Some Options
A. Use an Existing Coordinate System
• State Plane or UTM
B. Create a Coordinate System to Minimize Distortion
1. Modify an existing system – State Plane/UTM
2. Modify the ellipsoid – Effectively altering the datum
3. Develop a modern Low Distortion Projection system such as those in Iowa, Kansas, Indiana, or Wisconsin
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Controlling Distortion
1. Modify Existing System
State PlaneEarth Surface
Ellipsoid
1. Modify Existing System
2. Modify the Ellipsoid
Controlling Distortion
Earth SurfaceEllipsoid
Controlling Distortion
1. Modify Existing System
2. Modify the Ellipsoid
3. Create a Low Distortion Projection (LDP)
Earth SurfaceEllipsoid
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Some Options
Coordinate System OptionsIt’s about understanding and managing distortions
• Do Nothing… not so good
• State Plane or UTM… good for large areas (statewide)
• Low Distortion Projections… good for small areas (local)
Purpose of Today’s Presentation
• Cover some coordinate system basics
• Look at available methods and options
• Review a brief history of coordinate systems in MN
• Look at the future of the County Coordinate system
• Discuss State Plane for 2022
Brief History in MN
1930s & ‘40s – State Plane
1960s – Modify State Plane
1970s – Modified State Plane/Roscoe project system
1980s – Minnesota County Coordinate System
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Minnesota Dept of Highways Datum
A modified system based on State Plane
State PlaneEarth Surface
Ellipsoid
Minnesota Dept of Highways Datum
• Developed in early 1968• Zones generally follow SPCS
Distortion Goals:1:10,000 (rural)1:20,000 (urban)
Minnesota Project Coordinate System
• Developed in early ‘70s• Zones defined by:
• 1° Long. / 15’ Lat.• Conforms to USGS
Distortion Goals:1:30,000
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A modified ellipsoid system to achieve low distortions
Minnesota County Coordinate System
Earth SurfaceEllipsoid
Minnesota County Coordinate System
• Developed in 1985• Zones generally defined by county boundaries
Distortion Goals:1:50,000 (rural)1:100,000 (urban)
Minnesota County Coordinate System
• 87 Counties
• 67 unique ground planes
• Low distortions ≈0.10ft/mileor better
• Secant planes
• Modified ellipsoids
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Minnesota County Coordinate System
County Plane Coordinate System Project
Conducted by Steven Rick Brown June 1984 – March 1985• Followed methods promoted by NGS
• Preliminary work done by hand• Specific programs were developed to speed analysis
• Reliance on USGS quad maps for elevations and positions (lat/long)
Minnesota County Coordinate System
Purpose of Today’s Presentation
• Cover some coordinate system basics
• Look at available methods and options
• Review a brief history of coordinate systems in MN
• Look at the future of the County Coordinate system
• Discuss State Plane for 2022
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Earth SurfaceEllipsoid
• Smaller zones
• Multiple names for single set of parameters
• Difficult to model parameters in modern software
• Inconsistent with modern practice – i.e., modified ellipsoid & secant to ellipsoid
Current County Coordinate System
Challenges with the existing County Coordinate System
Earth SurfaceEllipsoid
Benefits of Modernizing
Low Distortion Projection
• Larger zones with similar performance to Cnty Coord.
• Eliminates the issues with a modified datum
• Works seamlessly with modern software
• Regional approach reduces the number of transition zones
• May be accepted by NGS
Modern Low Distortion Projection (LDP) system
Current County Coordinate System
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Iowa Regional Coordinate System
Kansas Regional Coordinate System
Minnesota Regional Coordinate System
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Criteria for Consideration
• Determine acceptable distortion: ≈ 20ppm or 0.10ft/mile
• Consider project area & terrain relief: ≈ 70 miles wide and 800ft vertical differential
• Determine best projection:Lambert Conformal Conic & Transverse Mercator
• Break on county boundaries
Criteria for Consideration
• Other Considerations:
• Transportation corridors• Geographical limiters: rivers, lakes, bluffs, etc.• Urban areas: Mankato, Moorhead, St Cloud, Minneapolis/St Paul
• Resource sharing: Dodge/Goodhue, Lac Qui Parle/Chippewa
• County partnerships: Stearns/Sherburne/Wright• GIS regional groups… to a lesser degree
Our Old Friend… Distortion
Source: Oregon Coordinate Reference System, Handbook and User Guide, available at ftp://ftp.odot.state.or.us/ORGN/Documents/ocrs_handbook_user_guide.pdf
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Example Distortion Maps
Example Distortion Maps – Changing Plane Ht.
Central Meridian: 94°22’, Ht:225m Central Meridian: 94°22’, Ht:275m
Central Meridian: 94°15’, Ht:275m Central Meridian: 94°30’, Ht:275m
Example Distortion Maps – Changing Meridian
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Central Meridian: 94°24’, Ht:250m Three Regions Instead of One
Example Distortion Maps – Changing Meridian
Two Zone Metro
Single Zone
Example Distortion Maps – Metro Options
Project Timeline
1. 2015 – Began with an initial report
2. 2016 – Stagnated, some discussion
3. 2017 – Staffing changes, recognized need, debate in‐house vs. outsourcing
4. 2018 – Created TAP group, developed preliminary design criteria, creating preliminary maps and data for review
5. 2019 – Will refine design criteria, finalize regions, complete parameters by December 2019, feedback and outreach
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Purpose of Today’s Presentation
• Cover some coordinate system basics
• Look at available methods and options
• Review a brief history of coordinate systems in MN
• Look at the future of the County Coordinate system
• Discuss State Plane for 2022
MnDOT’s Proposal
February 2018 – MnDOT began efforts to propose a single State Plane zone.
• Met with MSPS Board, MnGEO, and DNR
• Letter included in Minnesota Surveyor, summer 2018, Vol. 28, No. 1
State Plane Background Information
A Little History
• Developed in 1930s
• Considered a practical solution for engineering
• Three zones in MN
• Distortions ≈ 1:10,000 on the ellipse or ≈ ½ ft/mile
• Never really “took off”
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UTM 15 for Statewide & Regional Mapping
• UTM misused for statewide mapping
MN Spatial Data Exchange Standard
UTM Background Information
• UTM misused for statewide mapping
• Becomes problematic when using GPS and online positioning services
• Distortions ≈ 1:2,500 that’s ≈ 2 ft./mile
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Single State Plane Zones
Other states with a single zone:
• Montana• Nebraska• Tennessee• South Carolina
Justification for a Single Zone
• Current SPCS not used
• UTM is misused
• Simplify legislation
• NGS will do the work
• Provide a legitimate coordinate system for regional and statewide planning purposes
Timeline and Next Steps
1. Development of new reference frame (datum) in 2022 is driving this proposal and timeline
2. NGS has indicated that a single zone for Minnesota will be developed without requiring an “official” request
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Links to Federal Register &NGS Policy, Procedure, and SPCS website
• NGS State Plane Coordinate System website ‐https://www.ngs.noaa.gov/SPCS/index.shtml
• History of State Plane ‐ NGS Policy ‐https://www.ngs.noaa.gov/library/pdfs/NOAA_SP_NOS_NGS_0013_v01_2018‐03‐06.pdf
• NGS Draft Policy ‐https://www.ngs.noaa.gov/INFO/Policy/files/DRAFT_SPCS2022_Policy.pdf
• NGS Draft Procedure ‐https://geodesy.noaa.gov/INFO/Policy/files/DRAFT_SPCS2022_Procedures.pdf
Summary
• Covered some coordinate system basics
• Looked at available methods and options
• Reviewed a brief history of coordinate systems in MN
• Looked at the future of the County Coordinate system
• Discussed State Plane for 2022
Questions?
Geoff Bitner, LS
651‐366‐3490