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BPA Regional Meetings
The Use of GPS in CPE
by Gary Smith BEng PGDip MSc CEng MCIHT MILT MIPP
Technical Details Supplied by Korec & Trimble
www.garykaysmith.co.uk
Presentation Outline
We Will Cover:
• Principles of GPS
• CPE Applications
• Planning
If Time Permits We Will Also Cover:
• Sources of Error
• Accuracy Factors
• Differential GPS
Principles of GPS
Introduction to GPS
?
The Global Positioning System (GPS)
• Developed by the American Department of Defence (DoD)
• ALL WEATHER, 24 Hour, worldwide time and positional information service
• Minimum of 4 Satellites required for a position
• 3 Segments: Control; Space: User:
Control Segment
Space Segment
User Segment
Segments
Control Segment
• Monitors and controls satellite orbits
• 1 Master control station ( Colorado Springs USA )
• 12 Monitoring Stations
The Global Positioning System
Space Segment
• 28 Satellites• 22,000km above the
earth• 12 Hour Orbits
How does GPS Works ?
4 or more satellites required Travel time of GPS
Distance= Speed x Time
Principle of Trilateration
The Global Positioning System
User Segment• Receive signals from Space
Segment• Information is used to
determine our position• CPE Applications ???
CPE Applications
?
CPE Applications• CCTV Smart Car
Enforcement of Bus, Parking & Traffic Contraventions using either:
Attended or Un-Attended Mode
• Digital GPS Camera
Positional Condition Survey
Enforcement of Parking Contraventions
• XT / XH DGPS systems
• RTK GPS Systems
Positional Location of Signs & Lines (& Any Asset)
CPE Applications
• Autonomous (10-15m)
E.g. GPS Sat Nav
• DGPS (Differential)(0.5 - 3m)
E.g. CCTV Smart Car & Digital GPS Camera
• “Float” (Meter to decimeter)
E.g. GPS Handheld Systems
• “Fixed” (1-3cm)
E.g. R8 GPS/GNSS System
CCTV Smart Car
Digital GPS Camera
Digital GPS Camera
Digital GPS Camera
Digital GPS Camera
XT / XH DGPS systems
RTK GPS Systems
GPS Surveying
Google Earth View of Surveying
Google Earth View of GPS Surveying
GPS Surveying Transferred to FastMap
GPS Surveying Transferred to MapInfo
MapInfo Transferred to ParkMap
Planning
?
Planning GPS
Planning GPS & GNSS
Sources of Error
?
Sources of Error
These factors cannot be controlled!
• Obstructions
• Multipath
Obstructions
Multipath
Accuracy Factors
?
Accuracy
These factors can be controlled by the GPS receiver:
• Satellite Geometry
• Elevation Mask
Satellite Geometry (DOP)
• A measurement of satellite dispersion relative to each other
• Often measured in DOP (Dilution of Precision) –Standard deviational spread of satellites.
• Lower the DOP the more spread out the satellites are relative to each other
• Lower the DOP the greater the accuracy• To obtain sub meter accuracy, a Positional DOP
(PDOP) of 6.0 less is requiredAccuracy Factors
Good Satellite Geometry (DOP)
Accuracy Factors
Poor Satellite Geometry (DOP)
Accuracy Factors
Elevation Mask
15 Degrees above the horizon
Atmosphere
Accuracy Factors
Controlling Accuracy Factors
• DOP value of less than 6.0
• Signal to Noise Ratio greater 4.0
• Elevation mask of 15o
Speed or Accuracy…?
Accuracy Factors are controlled by a simple Slider Bar in FastMAP
Differential GPS
?
Differential GPS (DGPS)
• GPS Positions on their own are often referred to as Autonomous (uncorrected).
• Autonomous GPS will give you typically 10-15m
• To improve this we need to perform some form of Differential correction to our GPS positions (DGPS)
Real Time DGPS
• A means of applying differential corrections whilst collecting GPS positions at the Rover
• Requires direct communication to a base or ground control station
Correction onlyRover Base
VRS – (Virtual Reference Station)
Trimble VRS NOW
– Real-time RTK / DGPS correction service provided by Ordnance Survey & Trimble’s Network of Base stations.
– Corrections provided by GPRS/3G– Requires a subscription fee & mobile
phone costs– 30cm accurate with XT / XH DGPS
systems– cm accurate with RTK GPS Systems
VRS – How it works – 3 Steps• 1) Rover receiver sends VRS
server its location from 5 or more satellites
• 2) VRS finds 3 nearest base stations and creates virtual base station within 10km of the Rover
• 3) VRS Server sends back DGPS corrections the Rover
Any Questions?
Company ProfileGary Kay Smith Ltd was established in 2005 to match the Key Skills of its founders as Business Management Consultants with Specialist Aspects including:
Business Management
Consultancy
Communications
Training
Consultancy Services
Business Management
Financial Management• Change Control• Financial Analysis• Benchmarking• Value Engineering• Business Case Preparation, Monitoring & Review
Project Management• Prince2 Philosophy• MS Project & MS Excel Project Plans
www.garykaysmith.co.uk
Consultancy Services
Consultancy
Highway Development• Planning application assessments• Transport impact assessments• Parking accumulation surveys• Asset surveying & mapping (inc Landscaping, Street Furniture & Trees)
Parking• Traffic Management Act 2004 specialist advice• Business case preparation• CPE feasibility business plan and implementation• Review of Parking Controls (inc GIS mapping of asset data)
Traffic and Transportation• Accident analysis• Junction design• Road space solutions• Traffic Sign Design and Traffic Regulation Orders• Public Consultation including statistical analysis of results www.garykaysmith.co.uk
Consultancy Services
Communications
Analysis• Spatial Analysis• Demographic Analysis• Equality & Diversity Analysis• Response Analysis• Customer Feedback
Consultation• Presentations• Workshops• Workgroups• Mystery Shopper• Postal Surveys• Door to Door Surveys• One to One Interviews
www.garykaysmith.co.uk
Consultancy Services
Training
City & Guilds & Edexcel Approved Centre• CCTV• Civil Enforcement Officers (plus Notice Processing & Supervisors)• Community Wardens (plus Accredited Persons)• Conflict Management• Customer Service• Health & Safety in the Workplace • ILM Centre (Team Leading, Leadership & Management)• NVQ Centre • Security Guarding
City & Guilds GOLA Centre• Mobile testing facilities using our suite of laptop computers
One Day Technical Courses• In house course tailored to our Clients Needs
www.garykaysmith.co.uk
Introduction To Key Staff
Gary Smith is the Managing Director of Gary Kay Smith LtdGary is a former Parking ManagerHe is a Chartered Engineer, Masters Qualified with over 25 yearsIndustry related experience in Highways, Parking, and Traffic & TransportationIn both Public and Private Sectors
Kay Smith is a Director of Gary Kay Smith LtdKay is a former Assistant Parking ManagerShe is a Degree Qualified Engineer with over 15 yearsIndustry related experience in Highways, Parking, and Traffic & TransportationIn both Public and Private Sectors
Danny Purton is the Business Manager & Quality Co-ordinatorDanny is a former Head of ServiceHe is a Chartered Engineer with over 40 years Industry related experience in Business Management, IT and Quality Systems
Peter Matthews is the Office & IT ManagerPeter is a former IT SpecialistHe has over 20 years industry related experienceIn the GIS/GPS Surveying, IT and Parking Sectors www.garykaysmith.co.uk
Contact Us
W: www.garykaysmith.co.uk
T: (01279) 417148
F: (01279) 417250
M: 07939337355
A: Allen House 1st FloorEdinburgh WayHarlowEssex CM20 2HJ
www.garykaysmith.co.uk
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