GPS Surveying Measurement Techniques

Learning Objectives

After completing this lecture you will After completing this lecture you will be able to:be able to:

Explain several phase observation Explain several phase observation techniques commonly used by surveyorstechniques commonly used by surveyors

Lecture OutlineIntroductionIntroductionClassic StaticClassic StaticFast/Quick/Rapid StaticFast/Quick/Rapid StaticPP KinematicPP KinematicRTKRTKConclusionConclusion

Introduction

Various measurement techniques - 4 most common to phase observableClassic Static SurveyingFast/Rapid/Quick Static SurveyingPost Processed Kinematic SurveyingReal Time Kinematic Surveying (RTK) Not post processed but can be done as

well

PPS Requirements10:30 10:35

Static GPS SurveyingStatic GPS Surveying

Classic StaticOriginal GPS Surveying TechniqueObserve 30 minutes + of dataRegular intervals (e.g. 15 seconds)Data processed in software after the event (Post Processed)Used for Highest Order Control Surveys and / or

for Long Lines - e.g. 100km Network Deformation Surveys Bringing control into a project area over

distances longer than 10km

Fast StaticAlso - Rapid Static or Quick StaticEvolved from Static Technique but uses more intelligent ways to solve ambiguitiesTypically for lines under 10kmObservation times from 5 to 15 minutes depending on line length and satellite number and geometryPost Processed5mm + 1ppm horizontal

Uses of Fast Static

Used for Higher Order Control Surveys for lines less than 10km -e.g. 3 - 5km Networks or by Local Authorities at 1km or lessDensifying Control (within 10km) for Local Authority Requirements Mapping Engineering Mine sites DCDB Upgrade

Static / Fast Static ExampleStatic / Fast Static Example

2 Receivers5 SVs

10:00 11:00 12:00 1:00

Base 1

Static / FastStatic Example

2 Receivers5 SVs

10:00 11:00 12:00 1:00

Base 2

Completed SurveyCompleted Survey

2 Receivers5 SVs

10:00 11:00 12:00 1:00

All points must have an independent check redundant observations

Post Processed Kinematic

Once Ambiguity is known and lock maintained, centimetre precision possible even while movingRequires initialization to solve ambiguities at start and when signal is lostPost ProcessedStop and Go mode occupation time measured in seconds (contour and detail)Used in Continuous mode for Railway Lines and GPS Controlled Photogrammetry

10:00 10:30

Loss of Lock!

PP Kinematic ExamplePP Kinematic Example

$#@%!

New Poi

nt Init

10:00 10:30

Loss of Lock!

Begin OTFInitialization 5 SVs

OTF InitializationComplete

Known Point Initialization

PP Kinematic Example

10:00 10:30

Loss of Lock!

PP Kinematic Example

Completed Survey

Real Time Kinematic (RTK)

Similar to PPK but Phase Data sent from Base by Rad ioCan be Initialized with Ambiguity on the Fly (OTF)Range typically up to 10kmShort occupation time means: Centimetre rather than millimetre precision Sensitive to number of satellites and their geometr y multipath can have major effect

Communications is a major limiting factorChallenge to Total Stations

Base Base ReceiverReceiver Remote ReceiverRemote Receiver

Broadcast Broadcast Raw DataRaw Data

USES of RTK

Local Connections, Cadastral, Engineering, Mining, Hydrographic, contour and detailGiven real time - set out is possibleEven if real time is not essential -cuts back on processing Avoid radiation fever (redundancies)Can post process as well for QA

RTK RequirementsRTK Requirements

RTK Rovers

VRS Base System

On-The-Fly InitializationRove until the unit is

in FIXED modeRoving time will depend

on the environment

Requires atleast 5 SVs inview to both

receivers

RTK ExampleRTK Example

Loss of Lock!

$#@%!

OTF Initialization

RTK Example

Known Point

Initialization

Loss of

lock!

Radial Survey

Completed Survey

All points must have an independent check redundant observations measure from another base!

Conclusion

You can now:You can now: Explain several phase observation Explain several phase observation

techniques commonly used by techniques commonly used by surveyorssurveyors

Self Study

Read relevant module in Study BookRead relevant module in Study BookDo self assessment quizDo self assessment quiz

Review QuestionsReview Questions