THE FUTURE OF STATE PLANE COORDINATES AT ODOT

Transcription

1 THE FUTURE OF STATE PLANE COORDINATES AT ODOT BY: RAY FOOS P.S. AND BRIAN MEADE P.S. THE OHIO DEPARTMENT OF TRANSPORTATION WORKING WITH STATE PLANE COORDINATES OR HOW TO MAKE THE EARTH FLAT SURVEYORS AND MAP MAKERS HAVE HAD TO CREATE MAPS OF THE EARTH FOR CENTURIES. THE WAY WE DRAW A CURVED SURFACE ON A FLAT PLAIN IS BY USING MAP PROJECTIONS. AS SURVEYORS WE ARE AWARE THAT WE CANNOT REPRESENT A CURVED SURFACE ON A FLAT PLAIN WITHOUT SOME DISTORTION. 1

2 THE CURRENT STATE PLANE COORDINATE SYSTEM DEVELOPED ALMOST 100 YEARS AGO (NAD 27) 158 MILE WIDE ZONES LINEAR DISTORTION DESIGNED AT 1:10,000 DISTORTION DUE TO ELEVATION ADDS TO THE TOTAL, REDUCING THE ACCURACY EVEN MORE NEED TO SCALE GRID DISTANCES TO GROUND TO ACHIEVE ACCURACIES NEEDED WITH TODAYS MODERN EQUIPMENT (GPS = TOTAL STATION) OHIO STATE PLANE COORDINATE SYSTEM LATITUDE N NORTH ZONE LATITUDE N ORIGIN LAT X=600,000 m, Y=0 m CENTRAL MERIDIAN LONGITUDE W LATITUDE N SOUTH ZONE LATITUDE N ORIGIN LAT X=600,000 m, Y=0 m 2

3 Linear distortion due to Earth curvature Projection (secant) Ellipsoid Grid length greater than ellipsoidal length (distortion > 0) Grid length less than ellipsoidal length (distortion < 0) Maximum projection zone width for balanced positive and negative distortion Linear Distortion due to Curvature and Elevation Ground Projection (secant) Ellipsoid Grid length greater than ellipsoidal length (distortion > 0) Grid length less than ellipsoidal length (distortion < 0) Maximum projection zone width for balanced positive and negative distortion Dave Minkel and Michael Dennis NGS/NOAA 3

4 ISSUES WITH THE USE OF CURRENT STATE PLANE COORDINATE SYSTEM: CURRENT STATE PLANE COORDINATE SYSTEM DESIGNED AT 1 : 10,000 ACCURACY TODAYS EQUIPMENT IS MUCH MORE ACCURATE THAN THIS OAC : SETS THE MINIMUM STANDARD FOR BOUNDARY SURVEYS AT 1 : 10,000 MINIMUM ACCURACY. THIS EATS UP YOUR ERROR BUDGET RATHER QUICKLY THIS SCALING IS DONE ON A PROJECT BY PROJECT BASIS NO STANDARD SCALE FACTOR USED FOR MULTIPLE PROJECTS PROJECTS IN CLOSE PROXIMITRY TO EACH OTHER HAVE DIFFERENT SCALE FACTORS AND DO NOT FIT EACH OTHER GRID DISTANCES DO NOT REFLECT TRUE GROUND DISTANCES DOES NOT WORK SEAMLESSLY WITH OTHER PRODUCTS (GOOGLE EARTH, ESRI, OSIP IMAGERY, CADD PLATFORMS) LINEAR DISTORTION IN OHIO NORTH ZONE Ohio North Zone Grid to Ground Combined Scale Factor Calculations Latitude Elevation Combined Scale Factor Distance variation in 1000' Location N 40-12'-55" 930 ' Delaware South N 40-26'-02" 946' Delaware/Marion N 40-42'-09" 945' Marion/Wyandot N 40-59'-38" 956' Wyandot/Seneca N 41-15'-19" 785' Seneca/Sandusky N 41-27'-14" 574' Sandusky/Ottawa N 41-42'-00" 558' North Bass Island 4

5 WAYS WE ARE HANDLING THIS CURRENTLY: SCALE INDIVIDUAL PROJECTS TO GROUND BY CALCULATING A COMBINED SCALE FACTOR EFFECTIVELY RAISES MAPPING PLANE TO MATCH GROUND SURFACE SCALED GRID DISTANCES GROUND DISTANCES GPS EQUIPMENT AND TOTAL STATIONS WORK SEAMLESSLY TOGETHER STAYING ON GRID NO SCALING SOMETIMES USED ON SMALL PROJECTS SOMETIMES USED ON PROJECTS CLOSE TO THE STANDARD PARALLELS DISTORTION IS IGNORED AND ADDED DIRECTLY TO YOUR ERROR BUDGET GPS EQUIPMENT AND TOTAL STATIONS DO NOT WORK WELL TOGETHER PRETEND IT DOESN T EXIST IS IT TIME TO RE THINK STATE PLANE COORDINATES? IS THERE A BETTER WAY? CAN WE DEVELOP A COORDINATE SYSTEM THAT WOULD ESSENTIALLY ELIMINATE DISTORTION (OR MAKE IT SO INSIGNIFICANT THAT IT CAN BE IGNORED)? CAN WE WORK SEAMLESSLY BETWEEN OUR GPS EQUIPMENT AND TOTAL STATION WITHOUT CALCULATING A SCALE FACTOR? CAN WE INCORPORATE GIS DATA INTO OUR SURVEYS (OR INCORPORATE OUR SURVEYS INTO GIS) SEAMLESSLY? 5

6 THE ANSWER IS: YES WE CAN! HOW? OHIO STATE PLANE COORDINATE SYSTEM LET S RE THINK HOW WE PROJECT LAT/LONG TO PLANE COORDINATES 6

7 BY LOOKING AT OUR STATE IN A DIFFERENT WAY INSTEAD OF DIVIDING OHIO INTO TWO ZONES (NORTH AND SOUTH) LET S LOOK AT HOW CURVATURE AND ELEVATION AFFECT LINEAR DISTORTION: LINEAR DISTORTION DUE TO CURVATURE: MAXIMUM ZONE WIDTH FOR SECANT PROJECTIONS MAXIMUM LINEAR HORIZONTAL DISTORTION MILES Parts per Million Feet per Mile Ratio 35 MILES ± 5 ppm ± 0.03ft. / mile 1 : 200, MILES ± 10 ppm ± 0.05ft. / mile 1 : 100, MILES ± 20 ppm ± 0.10ft. / mile 1 : 50, MILES ± 50 ppm ± 0.30ft. / mile 1 : 20, MILES ± 100 ppm ± 0.50ft. / mile 1 : 10,000 Dave Minkel and Michael Dennis NGS/NOAA 7

8 LINEAR DISTORTION DUE TO ELEVATION: HEIGHT ABOVE AND BELOW PROJECTION SURFACE LINEAR DISTORTION DUE TO ELEVATION FEET Parts per Million Feet per Mile Ratio ± 100 ft. ± 4.8 ppm ± 0.03ft. / mile 1 : 209,000 ± 400 ft. ± 19 ppm ± 0.10ft. / mile 1 : 52,000 ±1,000 ft. ± 48 ppm ± 0.25ft. / mile 1 : 21,000 Dave Minkel and Michael Dennis NGS/NOAA Ground Typical State Plane (secant) Low Distortion Ellipsoid Low Distortion Projection Grid length greater than ellipsoidal length (distortion > 0) Grid length less than ellipsoidal length (distortion < 0) Typical State Plane Zone width for balanced positive and negative distortion Dave Minkel and Michael Dennis NGS/NOAA 8

9 LOW DISTORTION PROJECTIONS A LOW DISTORTION PROJECTION MINIMIZES THE DIFFERENCE BETWEEN THE GRID AND GROUND DISTANCES BY CREATING A MINNIE STATE PLANE TYPE PROJECTION OVER A SMALLER AREA THAN WHAT IS TYPICALLY DONE. THIS ALLOWS THE USER OF THE LDP TO CONVERT WGS 84 COORDINATES (LAT/LONG) TO A PLANE COORDINATE SYSTEM (LDP) WITH LITTLE EFFORT. THE END USER SELECTS HIS/HER COUNTY PROJECTION AS SIMPLY AS SELECTING OHIO NORTH OR SOUTH ZONE. LOW DISTORTION PROJECTIONS THE NEW LOW DISTORTION PROJECTION SYSTEM WE ARE PROPOSING AT ODOT IS BASED ON COUNTY BOUNDARIES BY USING COUNTY BOUNDARIES (TYPICALLY MILES WIDE) WE MANIPULATE OUR CENTRAL MERIDIAN AND SCALE FACTOR TO TWEAK THE PLANE TO CLOSELY MATCH THE SIZE AND GENERAL TERRAIN OF THE COUNTY. DISTORTION BETWEEN GRID AND GROUND FOUND IN OUR TESTING IS ROUGHLY 1:300,000 IN OUR NORTHERN FLATLANDS AND 1:50,000 IN OUR SOUTHEASTERN HILLS 1:300,000 9

10 LOW DISTORTION PROJECTIONS PROJECTIONS ARE DESIGNED BASED ON THE SHAPE OF THE COUNTY. COUNTIES THAT LIE PREDOMINANTLY EAST AND WEST RECEIVE LAMBERT CONFORMAL CONIC PROJECTIONS MAHONING LOW DISTORTION PROJECTIONS COUNTIES THAT PREDOMINATELY LIE NORTH AND SOUTH RECEIVE TRANSVERSE MERCATOR PROJECTIONS. SUMMIT 10

11 LOW DISTORTION PROJECTIONS WORK FLOW FOR SURVEYORS USING A LOW DISTORTION PROJECTION IS AS SIMPLE AS SELECTING THE COUNTY YOU ARE WORKING IN. NO CALCULATING SCALE FACTORS PROJECTS WITHIN A COUNTY ALL FIT SEAMLESSLY TOGETHER GEODETIC TOOL KITS AND EQUIPMENT MANUFACTUER S SOFTWARE HANDLE THE PROJECTION. WE ARE NOT THE FIRST TO COME UP WITH THIS: Oregon has regional Low Distortion Projection Zones established that minimize distortion based on topography. Iowa also has regional Low Distortion Projection Zones Wisconsin and Indiana have Low Distortion Projections based on county boundaries similar to what we are proposing. 11

12 WISCONSIN: WISCRS INDIANA: INGCS 12

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15 THE PROOF IS IN THE TESTING: OHIO NORTH STATE PLANE COORDINATES: STATION PURDY TO PINE GRID DISTANCE = GROUND DISTANCE = RESULT = FEET PER MILE 1 : 10,000 LOW DISTORTION PROJECTION COORDINATES: STATION PURDY TO PINE GRID DISTANCE = GROUND DISTANCE = RESULT = FEET PER MILE 1 : 333,000 15

16 WHAT ABOUT MICROSTATION? FUTURE GOALS THE GOAL WILL BE TO HAVE SEED FILES SET UP WITH ALL OF THE LDP PROJECTIONS. WHEN YOU CREATE YOUR PROJECT IN THE ODOTcadd_CreateNewProject VBA THE CUSTOM GEOGRAPHIC COORDINATE SYSTEM FILE WILL BE AUTOMATICALLY SET IN THE DRAWING. QUESTIONS? COMMENTS? WHERE DO WE GO FROM HERE? 16