Geodetic Networks And Survey Control For Large Projects

Geodetic NetworksAnd Survey Control ForLarge ProjectsMaryland Society of SurveyorsSpring Technical ConferenceBy: Alan R. DragooMaser Consulting P.A.March 2, 2015Maritime Institute of TechnologyTraining and Conference CenterLinthicum Heights, Maryland

2/18/2015Survey Control For Large ProjectsMaryland Society of SurveyorsAlan R. Dragoo PLSMaser ConsultingSterling, Virginia2015 Spring Technical ConferenceMarch 2, 2015Maritime Institute of TechnologyLinthicum Heights, MarylandAgenda Accuracies Advantages, Disadvantages and best practicesfor the following– GPS Static– OPUS Static– OPUS Rapid Static– Conventional Traverse– Conventional Leveling1

2/18/2015How are your accuracies going to beevaluated Absolute Relative Point to PointHow much confidence do you needName of errorProbableStandard DeviationTwo sigma or 95% errorValue0.6745 1 2 % Certainty50%68.3%95%2

2/18/2015What Accuracy Do You Need Horizontal Vertical– 3 Feet– 6 Feet– 0.03 Feet– 0.01 FeetIf Someone Else Is Going To EvaluateYour Data You better develop a way to test it before theydo.3

2/18/2015What Standards and Specifications areAvailable Standards and Specifications for GeodeticControl Networks Geometric Geodetic Accuracy Standards andSpecifications for Using GPS RelativePositioning Techniques Guidelines for Establishing GPS DerivedEllipsoid Heights (NOS NGS 58)What Standards and Specifications areAvailable Guidelines for Establishing GPS OrthometricHeights (NOS NGS 59) National Geodetic Survey User Guidelines forSingle Base Real Time GNSS Positions National Geodetic Survey Guidelines for RealTime GNSS Networks Minimum Standard Detail Requirements ForALTA/ACSM Land Title Survey 20114

2/18/2015Standards and Specifications Is there a project requirement that the surveyconform to a specific set of published“Standards and Specifications”.Planning The SurveySo You Can Price The Survey Investigate what existing NGS control isavailable. Recover existing NGS control. If necessary develop a plan to densify theprimary control so that error propagation willnot exceed your specifications. Plan your project survey control.5

2/18/2015Error Propagation Due To CenteringErrorsHorz AngleBack DistFwd DistTarget Centering ErrorInst Centering Error D1 D2 t 180 Deg600 Ft600 Ft t0.005 Ft c c 0.005 FTTravDist 52802.4 "3.4 "4.2 "206265 1 / 48,990 PrecisionTrav DistWhat Accuracies Can Be ExpectedGPS StaticRelative Accuracies Horizontal Vertical0.02 to 0.03 feet0.03 to 0.04 feetWITH PROOF THAT IT’S RIGHT6

2/18/2015Static GPS Network Design13204OPUS ‐ Static OPUS – Static 2 Hours toAbsolute Accuracies24 Hours0.09Vertical RMS0.08.cmRMS (Feet)0.070.06Horizontal Session Duration "T Hours" Results are at a 95% level of confidenceWith Good Conditions & No Proof7

2/18/2015What to Look For In a QualityOPUS – Static Solution Orbit used precise or rapid 90% observations used 50% ambiguities fixedCorrect antenna and antenna heightStatic: overall RMS 3 cm,Peak to peak errors 5 cm.OPUS – Static Quality IndicatorsSOFTWARE: page5 1209.04 master50.pl 022814START: 2015/01/30 16:53:00EPHEMERIS: igr18295.eph [rapid]STOP: 2015/01/30 19:15:00NAV FILE: brdc0300.15nOBS USED: 4693 / 5253: 89%ANT NAME: TRMR10NONE# FIXED AMB:31 /32: 97%ARP HEIGHT: 2.050OVERALL RMS: 0.021(m)REF FRAME: NAD GT:37 5 30.58862283 36 45.3478376 23 14.65217-33.184(m)3.278(m)Northing (Y) [meters]Easting (X) [meters]Convergence [degrees]Point ScaleCombined Factor0.008(m)0.046(m)0.017(m)IGS08 507.182(m)0.008(m)0.046(m)0.017(m)0.014(m)37 5 30.618370.014(m)0.014(m)283 36 45.329590.014(m)0.014(m)76 23 14.670410.014(m)0.046(m)-34.531(m)0.046(m)0.081(m) [NAVD88 (Computed using GEOID12A)]UTM COORDINATESUTM (Zone 79249STATE PLANE COORDINATESSPC (4502 VA 62128

2/18/2015How Can The OPUS – Static Positional ErrorBe Calculated to a 95% ConfidenceOPUS – Rapid StaticHow Accurate Is It?http://www.ngs.noaa.gov/OPUSI/Plots/Gmap/OPUSRS sigmap.shtmlAbsolute Accuracy With Good Conditions and No Proof9

2/18/2015What to Look For In a QualityOPUS – Rapid Static SolutionOrbit used precise or rapidCorrect antenna and antenna heightObservations Used 60%Quality Indicator 3 for both the “Networkmode adjustment” and the “Rover modeadjustment” Normalized RMS 1 Accuracies should be 0.050 OPUS – Rapid Static Quality IndicatorsSOFTWARE:EPHEMERIS:NAV FILE:ANT NAME:ARP HEIGHT:rsgps 1.37 RS93.prl 1.99.2igu18194.eph [ultra-rapid]brdc3240.14nTRMR10NONE2.000REF FRAME: NAD GT:40 24 48.70377285 30 39.7476274 29 20.25238-6.326(m)26.605(m)Northing (Y) [meters]Easting (X) [meters]Convergence [degrees]Point ScaleCombined Factor0.007(m)0.024(m)0.021(m)START: 2014/11/20 21:07:00STOP: 2014/11/20 22:04:30OBS USED: 3915 / 4518: 87%QUALITY IND.3.12/ 23.79NORMALIZED RMS:0.455IGS08 3049.577(m)0.007(m)0.024(m)0.021(m)0.006(m)40 24 48.736480.006(m)0.007(m)285 30 39.729710.007(m)0.007(m)74 29 20.270290.007(m)0.032(m)-7.585(m)0.032(m)0.034(m) [NAVD88 (Computed using GEOID12A)]UTM COORDINATESUTM (Zone 2413STATE PLANE COORDINATESSPC (2900 NJ 010

2/18/2015Accuracy for OPUS – Rapid StaticRelated Information Positions are reported at a 95% level ofconfidence. Accuracies are reported at a 1 sigma levelBe Sure To Get Your Antenna HeightRightIt is not always obvious11

2/18/2015Network RTK Network Accuracies Typical– Horizontal– Vertical2 – 3 cm ( 0.06 – 0.10 feet)3 – 5 cm (0.10 – 0.16 feet)With Good Conditions Observation Time 3 minutesConventional TraverseYour Accuracy and Confidence Will Depend On ManyThings: Density and accuracy of existing control Accuracy of angles and distances measured Quality of measurements Quality of setups Equipment properly adjusted Properly set stations for distance and visibility Type of adjustment performed12

2/18/2015Avoiding Problems With Refraction Sighting over or next to object that arewarmer than the surrounding air. Especiallythose that are closer to the instrument. Sighting over areas that have vertical air flowclose to the instrument.Solving A Refraction ProblemNon-refracted line ofsight to the top ofbuildingRefracted line ofsight from the topof buildingControl 2Azimuth 2Control 1Azimuth 1Point 11.Compute approx position of point 1 from Azimuth 1 for astro2.Compute astro azimuth Point 1 to Az Mk 3Az Mk 313

2/18/2015What Do The Specifications Say?Table 2.1 - Distance accuracy standardsClassificationMinimum distance accuracyFirst-order1:100,000Second-order, class I1: 50,000Second-order, class II1: 20,000Third-order, class I1: 10,000Third-order, class II1: rectionsNumber of positions168 or 12†6 or 8 *42Standard deviation of mean not to exceed0.4"0.5"0.8"1.2"2.0"Rejection limit from the mean.4"5"5"5"5"† 8 if 0.2", 12 if 1.0" resolu on.* 6 if 0.2", 8 if 1.0" resolution.What Is One AngleOr One Position? An angle is a direct and reverse pointing oneach targetOne AngleDR0 00 10180 0 15Mean12.5DR132 26 35312 26 2831.5Angle132 26 19.014

2/18/2015So How Many Angles Should You Turn 1 Angle (4 pointings) “NO CHECK” 2 Angles (8 pointings) There is a check but ifsomething is wrong you don’t know what. 3 Angles (12 points) Now you have somethingthat you can throw out if something is bad For large projects you should probable turn 6angles 24 pointing. “THINGS DO GO WRONG”Traverse Station Locations When setting stations for large projects setthe stations as far apart as possible and stillhave good visibility and quality angles. Don’t worry about whether you can see thethings you need to locate. You can setsupplemental control to do this later.15

2/18/2015Field Procedures Leap frog traverse (Right Way)– Move ahead– Relevel– Check centering If acceptable continue traverse If unacceptable return previous angle Traverse through and over stations withexisting horizontal or vertical values. Do not take side shots to existing stations.Use The Proper AdjustmentTechnique Compass Rule Adjustments introducedistortion errors into your traverse. Understand how and use a true Least SquaresAdjustment. This will give you a best fit toeverything you hold16

2/18/2015Conventional Leveling Your Accuracy and Confidence Will Depend On– Density and accuracy of existing control– Quality of equipment used– Tolerances for quality of measurements– Field procedures used– Equipment properly adjusted It’s the little things that countQuality of Level and Accessories 1st Order 2nd OrderTrimble DiNi 0.3Trimble DiNi 0.7 1st OrderInvar Rods Less than 3rd Order Folding Rods or FiberglassRods17

2/18/2015Leveling TolerancesOrderClassFirstIFirstSecondIIISection misclosures (backward and forward)SecondIIThirdOne‐Setup SectionE0.40mmE1.00mm‐‐ ‐‐ ‐‐ ‐‐‐‐ ‐‐ ‐‐ ‐‐‐‐ ‐‐ ‐‐ ‐‐Two runnings of a sectionless than 0.10 km in lengthE0.95mmE1.26mmE1.90mmE2.53mmE3.79mmAlgebraic sum of allcorrected sectionmisclosures of a levelingline not to exceed3 D4 D6 D8 D12 DSection misclosure not toexceed (mm)3 E4 E6 E8 E12 ELoop misclosuresAlgebraic sum of allcorrected misclosures notto exceed (mm)4 F5 F6 F8 F12 FLoop misclosure not toexceed (mm)4 F5 F6 F8 F12 F(D ‐‐ shortest length of leveling line (one‐way) in km)(E ‐‐ shortest one‐way length of section in km)(F ‐‐ length of loop in km)Leveling Field Procedures Use Leveling Pins18

2/18/2015Leveling Without a Pin When leveling andthe surface is notprecisely flat, if therod is not held atexactly the samelocation a systematicerror will occur. Remember you aremeasuring to 0.3 mmForesightBacksightLeveling Field Procedures Keep Sights Balanced Requirements forlines of Sightand balance.Lines of sightMaximum sighting distanceFirst Order First Order Second Order Second OrderClass 1Class IIClass IClass IIThird Order160 Ft195 Ft195 Ft230 Ft295 FtE15FtE33FtE15FtE33FtE33FtE33FtE33FtE33FtMaximum imbalancePer SetupPer SectionE6FtE13Ft19

2/18/2015Leveling Field Procedures Heat Shimmer UsuallyCancels in a BalancedSetup. Refraction does notCancel even with BalancedSetups. “No readings lessThan 1.5 ft”Leveling Field Procedures Using a Plug “ErrorsCancel”20

2/18/2015Leveling Field Procedures When using two rods label them “Rod 1” and “Rod2” Come of your known bench mark with “Rod 1” andgo into your known bench mark with “Rod 1” Leap frog your rodsRod 1Rod 2Rod 1Rod 2Rod 1Leveling Field Procedures Level through and over all existing benchmarks. Do not take side shots to existing benchmarks.21

2/18/2015Trigonometric Leveling Leveling Accuracy for 10 mile project– Normal Trig Leveling 0.15 Ft to 0.20 Ft– High precision Trig Leveling 0.08 Ft to 0.10 Ft– Careful Conventional Leveling 0.04 Ft to 0.06 Ft– Instrument used 1.0” RobotHigh Precision Trig Leveling Measure Hi’s in meters, centimeter andmillimeters. Measure all setups independently Do not carry forward measurements22

2/18/2015Questions:4523

Quality of Level and Accessories 1st Order Trimble DiNi 0.3 2nd Order Trimble DiNi 0.7 1st Order Invar