2-10-11 olsen armstrong-part4 gnss survey planning

7/29/2019 2-10-11 Olsen Armstrong-Part4 GNSS Survey Planning

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INTRODUCTION TO GPS

OSU GPS WORKSHOPFebruary 10, 2011

Michael Olsen, PhD -Assistant ProfessorMark L. Armstrong, PLS -NGS Oregon Advisor


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GPS survey goal, plan, and schedule

CORS (active marks)

National Spatial Reference System

OPUS-S, OPUS-RS, OPUS-DB (publishing)

Using passive marks

Mission Planning

PART IV - GPS Survey Planning


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GPS survey planning

What is the survey goal? Single point; small network; large networkProject specifications; standards (FGDC); accuracy requiredHorizontal and vertical datumGeoid model choice; hybrid or pure gravimetric

Survey Style; static; fast static; RTK; RTNWhat will control the survey?

CORS; HARN; other passive marks or a combination?What software will be used?

Then make a mission plan and schedule


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Standards for Geodetic Networks Federal Geographic Data Committee standards, Part 2

FGDC-STD-007.2-1998Maintained by the National Geodetic Survey

Sponsored by: Federal Geodetic Control Subcommittee

GPS survey planning cont.

http://www.fgdc.gov/standards/projects/FGDC-standards-projects/accuracy/part2/index_html


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Standards for Geodetic Networks Objectives

To provide consistency in reporting the accuracyof point geospatial data collected by differentactivities (e.g., geodetic surveying, topographicmapping, bathymetric mapping, facilitiesmanagement mapping, cadastral surveying, etc.)and develop a FGDC document with a singlemethodology that defines how to report thepositional accuracy for all point geospatial datacollected, produced, or disseminated by the

Federal government and the Nation.


http://www.fgdc.gov/standards/projects/FGDC-standards-projects/accuracy/part2/index_htmlhttp://www.fgdc.gov/standards/projects/FGDC-standards-projects/accuracy/part2/index_htmlhttp://www.fgdc.gov/standards/projects/FGDC-standards-projects/accuracy/part2/index_htmlhttp://www.fgdc.gov/standards/projects/FGDC-standards-projects/accuracy/part2/index_htmlhttp://www.fgdc.gov/standards/projects/FGDC-standards-projects/accuracy/part2/index_htmlhttp://www.fgdc.gov/standards/projects/FGDC-standards-projects/accuracy/part2/index_htmlhttp://www.fgdc.gov/standards/projects/FGDC-standards-projects/accuracy/part2/index_html


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Standards for Geodetic Networks Scope

Part 2 applies to accuracy reporting for geodeticnetworks. Geodetic control surveys are usuallyperformed to establish a basic control network(framework) from which supplemental surveyingand mapping work, covered in other parts of thisdocument, is performed. Geodetic networksurveys are distinguished by use of redundant,interconnected, permanently monumentedcontrol points that comprise the framework for

the National Spatial Reference System (NSRS) orare often incorporated into the NSRS.




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Standards for Geodetic NetworksTable 2.1 -- Accuracy Standards

Horizontal, Ellipsoid Height, andOrthometric Height---------------------------------------------Accuracy 95-PercentClassification Confidence---------------------------------------------Less Than or Equal to:

1-Millimeter 0.001 meters2-Millimeter 0.002 "5-Millimeter 0.005 "1-Centimeter 0.010 "2-Centimeter 0.020 "5-Centimeter 0.050 "1-Decimeter 0.100 "2-Decimeter 0.200 "5-Decimeter 0.500 "1-Meter 1.000 "2-Meter 2.000 "5-Meter 5.000 "10-Meter 10.000 "



When control points ina survey are

classified, they havebeen verified as beingconsistent withall other points in thenetwork, not merelythose within that

particular survey.


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Standards for Geodetic NetworksSection 2.2.2 -- Accuracy Determination Four Steps:

l. The survey measurements, field records, sketches, and other documentationare examined to verify compliance with the specifications for the intendedaccuracy of the survey. This examination may lead to a modification of theintended accuracy.2. Results of a minimally constrained, least squares adjustment of the surveymeasurements are examined to ensure correct weighting of the observationsand freedom from blunders.

3. Local and network accuracy measures computed by random errorpropagation determine the provisional accuracy. In contrast to a constrainedadjustment where coordinates are obtained by holding fixed the datum valuesof the existing network control, accuracy measures are computed by weightingdatum values in accordance with the network accuracies of the existingnetwork control.4. The survey accuracy is checked by comparing minimally constrainedadjustment results against established control. The result must meet a 95percent confidence level. This comparison takes into account the networkaccuracy of the existing control, as well as systematic effects such as crustalmotion or datum distortion. If the comparison fails, then both the survey andnetwork measurements must be scrutinized to determine the source of theproblem.



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Standards for Geodetic NetworksSection 2.2.3 -- Accuracy Reporting

When providing geodetic point coordinate data, a statement shouldbe provided that the data meets a particular accuracy standard forboth the local accuracyand the network accuracy.

For example, these geodetic control data meet the 2-centimeter localaccuracy standard for the horizontal coordinate values and the 5-centimeter local accuracy standard for the vertical coordinate values(heights) at the 95-percent confidence level. A similar statementshould be provided for these same data reporting the networkaccuracy.




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Horizontal and Vertical Datum

Horizontal DatumNAD 83(CORS96)Epoch 2002 [Current NSRS]

NAD 83(CORS96a)Epoch2010 [Mid 2011)

NAD 83(2007) [Most recent national adjustment of passive marks]

NAD 83(1998) [Oregon HARN]

Vertical DatumNAVD 88 [Current NSRS]

Geoid Models

Geoid09 [Current NSRS Hybrid Model]Geoid03 [Previous NSRS Hybrid Model]USGG2009 [Current NSRS Gravimetric Model]



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GPS (GNSS) Survey Styles

Static Survey > 20 minutes logging data at each station (typ. ~30-250km baselines)

Fast-Static Survey < 20 minutes logging data at each station (typ.

< 30km baselines)Both styles requires simultaneous observations for all stations in thecurrent session

Real-time kinematic Survey (RTK) Base station setuprequired with either radio or cell phone connection with all

rovers. Single base line differential correction performed

Real-time Network (RTN) Rovers communicate with RTNservers via cell phone data link. Network solution possible



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Continuous Operating Reference Stations (CORS)


The CORS term istied to the NGSand refers toofficial nationalstations wheredata for thestation is archivedon NGS serversfor all users.


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Oregon CORS and CGPS stations


~31 CORS in Oregon

~139 CORS + CGPS-11 MYCS CORS


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Other geodetic datum to constrain your networktoo


HARN = High Accuracy Reference NetworkPassive marks available in the NGSIDB via datasheets.

In Oregon the latest horiz. HARN datum = NAD 83(1998)Older Oregon HARN were in 86 and 91

NAD 83(2007) = The most current national

adjustment of ~70,000 passive monuments.

others


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In addition to choosing a datum you need tochoose a coordinate system made up of:

-map projection-geoid model


Oregon Station Plane Coordinate System (2 zones)Oregon Coordinate Reference System (20 zones - new 2010)UTM Zones

others


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GPS survey mission planning

Research available control

Set any new monuments for the network, and write

descriptions on how to get to and access the mark

Recon the site and make notes, sketches and visibilitydiagrams

Take digital photos of the monumentClose-up of the capHorizon shot of each setup on the monument


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Make notes, sketches and writedescriptions at all monuments observed


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Make a visibility diagram in the field


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Shows azimuth andelevation of obstructionsto satellites. This will be

used in planning softwareto optimize theobservation time scheduleso that satellites will beavailable.


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Observation data logging times based on the number ofsatellites available. These suggested times are still valid!


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From Trimble GPS Planning tool shows #SV and PDOP

PDOP = Position Dilution of PrecisionPDOP values considered goodfor positioning aresmall, such as 3. Values greater than 7 are

consideredpoor.


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Observation schedule shows: date; GPS day; sessionnumber; monument observed; observers name; observationlogging time (maybe same for each session or different)


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GPS Planning Additional Reading

http://www.ngs.noaa.gov/PUBS_LIB/pub_GPS.shtml

Guidelines for Establishing GPS-derived Orthometric Heights(Standards: 2 cm and 5 cm) NOAA TM NOS NGS-59 Zilkoski, D.B.,Carlson, E.E., & Smith, C.L. Mar 26, 2008 PDF

NGS User Guidelines for Single Base Real Time GNSSPositioning v1.0 Henning, W.E. Jan 2010 PDF

Guidelines for Establishing GPS-Derived Ellipsoid Heights- NOAA TM NOS NGS-58 Zilkoski, D.B., D'Onofrio, J.D., Frakes,

S.J. Nov 1997 PDF orHTML
http://www.ngs.noaa.gov/PUBS_LIB/NGS592008069FINAL2.pdfhttp://www.ngs.noaa.gov/PUBS_LIB/NGSRealTimeUserGuidelines.v1.1.pdfhttp://www.ngs.noaa.gov/PUBS_LIB/NGS-58.pdfhttp://www.ngs.noaa.gov/PUBS_LIB/NGS-58.htmlhttp://www.ngs.noaa.gov/PUBS_LIB/NGS-58.htmlhttp://www.ngs.noaa.gov/PUBS_LIB/NGS-58.pdfhttp://www.ngs.noaa.gov/PUBS_LIB/NGSRealTimeUserGuidelines.v1.1.pdfhttp://www.ngs.noaa.gov/PUBS_LIB/NGS592008069FINAL2.pdf


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GPS Planning Free Software Tools

Trimble Setup Planning Software v. 2.9Download at:

Download the latest ephemeris files, and almanacs at:

http://www.trimble.com/planningsoftware_ts.asp

http://www.trimble.com/gpsdataresources.shtml
http://www.trimble.com/planningsoftware_ts.asphttp://www.trimble.com/gpsdataresources.shtmlhttp://www.trimble.com/gpsdataresources.shtmlhttp://www.trimble.com/gpsdataresources.shtmlhttp://www.trimble.com/planningsoftware_ts.asp


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GPS Planning Free Software Tools

Ashtech Web Mission Planning Tool

http://asp.ashtech.com/wmp/


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Receiver

AntennaAntenna cablesRTK radio modem or cell phoneBatteriesBattery-to-receiver cablesBack-up batteries or cigarette light adaptorTripodsBipodsTribrachsTribrach adaptorsFlashlightMeasure tape or rodStation information

Observation log sheetsPaper and pencilTwo way radio or cell phoneObservation scheduleFlagging, paint, PK nails, hammerTraffic control equipment

Reference list

Emergency phonenumbers

names, addresses,telephone numbers of

private-property ownersrelevant to this

projectGate keys or combinationsMaps

If you plan to download andprocess data in the field, bringthe following materials.

Data CollectorLaptopMemory PC CARDs etc.

Equipment Checklist


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Record your observationon every point.REMEMBER THAT THEANTENNA HEIGHT ISCRITICALLY IMPORTANT!!!


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NGS OPUS Suite of Programs

The Online Positioning User Service

Your easy access to the NSRS through:

OPUS-S (static) >2 - 48 hours of data required OPUS-RS (rapid static) >15 min. 2 hours of data required

OPUS-DB (publish your observation to the OPUS database)- 4+ hours required for submission using OPUS-S

OPUS-Project (baseline processing and adjustment of networks)-Under development


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How Good Can I Do With OPUS-S?

As a quality test,

2-hour data setsfrom more than200 CORS weresubmitted toOPUS-S and the

results comparedto the acceptedcoordinates.

Mean:


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rthOffsetfrom24

hr.Mean(m) 24 Hrs/160

Time Scatter Plots (Horizontal)


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More generally,Eckl et al.(NGS)preformed asimilar but

more extensivetest using thesame softwarebut outside

OPUS. Eckl et al., 2001, Accuracy of GPS-derived relative positions as a function of interstation distance andobserving-session duration, J. of Geod. 75, 633-640).

Their results provide a good rule of thumb foraccuracy versus session duration when using OPUS-Sand in many other applications.

How Good Can I Do With OPUS-S?


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How Does OPUS-S Work?

OPUS-S processing highlights:

Everything is done in the International TerrestrialReference Frame (ITRF).

SV coordinates are held rigidly fixed.CORS coordinates are heavily constrained.

Neutral atmosphere (tropo) dry component modeled.Neutral atmosphere (tropo) wet component estimated.Double-differenced, ion-free carrier phase observable.Carrier phase ambiguities are fixed to their integer values where

possible; float ambiguities are estimated otherwise.

Individual baselines are processed and the results combinedgenerating mean coordinates and peak-to-peakuncertainties.


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OPUS-S Uploads By Month

Valid as of 2010-03-30. Values before January, 2005 are approximate.

Shown here are

the monthlyupload countsto OPUS-S.

Submissions to

OPUS-Scomprise anon-trivialpercentage ofall hits on the

NGS web sites.

Average~15k/month

0

5000

10000

15000

20000

25000

30000

35000

40000

OPUS-S Uploads


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The OPUS-RS Interface

With OPUS-RS, the beautiful simplicity remained. In fact the entry

form is the same as for OPUS-S.

The user provides:

Their email address.

An antenna type.The vertical offset to the ARP.15-minutes to 2-hours of GPS L1 + L2 data.

The user receives:

Coordinates accurate to a few centimeters.


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The same interface is used except one clicks theUpload to RAPID-STATIC button instead.

The OPUS-RS Interfacehttp://www.ngs.noaa.gov/OPUS/

http://www.ngs.noaa.gov/OPUS/


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How Good Can I Do With OPUS-RS?

http://www.ngs.noaa.gov/OPUSI/Plots/Gmap/OPUSRS_sigmap.shtml

The OPUS-RS Accuracy and Availability Tool.


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1 for each 0.2 degree grid.

Horizontal and vertical standarderrors for 15 minutes and1-hour length data.

Inverse Distance Weightingmethod to interpolate the sigmas.

Areas outside the color overlayare where there are less thanthree active CORS sites within250 km range. OPUS-RS willusually fail at these locations.

Automated Weekly update

Use updated CORS list andobservation data availability

Global coverage including non-USterritories.

How Good Can I Do With OPUS-RS?


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How Does OPUS-RS Work?

OPUS-RS selects three to nine best CORS based upon:

Having common satellite visibility with the userdata.

Having distances from the users site


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How Does OPUS-RS Work?

In addition, users site must be no more than 50 km from the

(convex) polygon created by the selected CORS.

Again in this figure, the star represents the users site; thetriangles are CORS. Five CORS and their resulting polygon areshown in this example.

If the users site, the star, ismore than 50 km outsidethis polygon, alternateCORS will be considered.

If none can be found,the processing will abort.

Schwarz et al., Accuracy assessment of the National Geodetic

Survey's OPUS-RS utility, 2009, GPS Solutions, 13(2), 119-132.


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OPUS-DB Interface

The view tab on the OPUShome page provides access tothe results stored in the data

base.


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QUESTIONS ?

2-10-11 olsen armstrong-part4 gnss survey planning

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