HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Experiences With Kinematic GPS Surveys in Developing Countries Dr Christopher Bennett

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company An Introduction Consultant to World Bank –Preparing Terms of Reference –Executing Surveys Developer of the ROMDAS road measurement system –Used for kinematic GPS and other data collection –130+ systems in over 30 developed and developing countries

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Overview A road engineer’s view of centreline surveys Some experiences –Lao PDR –Samoa

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company A Road Engineer’s View of Centreline Surveys

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Role of GPS? Interface with data –GIS the most intuitive method Referencing the base network –GPS vs Linear Referencing data –GPS not suitable for all attributes

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Interfacing With Data GIS offers the most intuitive way of interfacing with data Layers can be used which reflect the desired level of detail

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Referencing the Road Network Historically roads referenced linearly In adopting GPS must provide link to existing data Use of GPS for referencing not practical for many types of data Need to carefully consider field procedures and staff capabilities

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company For Each Data Item Must Consider: PRECISION –Positional error using different technologies ACCURACY –The tolerance for the required position RESOLUTION –Level of detail EXTENT –Physical characteristics in terms of length, breadth and depth

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Must Ensure Meets a Logical Constraint

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Not Every Item Requires the Same Accuracy

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company NZ Example Level 1: (+/- 3 m) –Reference stations Level 2: (+/- 5 m) –Other referencing (section start) –High speed data (roughness, texture, skid) –Traffic facilities Level 3: (+/- 10 m) –Visual condition –Signs, roadmarkings –Structures –Accidents

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Not Every Item Should Be Referenced With GPS General rule: Only those data which are most suited to spatial referencing should be spatially referenced Examples of spatially referenced data: –Reference Stations and other key referencing features –The road centreline –Off road objects, such as signs, which cannot be referenced using linear system

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Remote Sensing vs Driving? Each method have a role For developing countries driving preferable because: –Often do not know which roads belong to the agency –Can collect additional data at same time –Can easily locate intermediate referencing markers ( eg km markers)

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Summary For most countries linear referencing will continue to be used by road engineers Need to adopt GPS technology to enhance road management Cannot underestimate: –Effort required to collect the data –Effort required to maintain the data –Effort required to use the data

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Opportunities and Challenges of Centreline Surveys In Developing Countries

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company The Situation Developing countries often do not have a proper record of their roads Maps are usually incomplete and out of date (if available at all!) Centreline surveys provide this information as well as other key data

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company ROMDAS Technology

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Technology Depends upon accuracy requirements Users have done surveys have been done with: –Garmin 12 channel consumer –Trimble Pro-XRS –Pro-XRS with Base Station –Pro-XRS with RTCM –OmniStar

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Accuracy? Comparison of Garmin GPS distance with DMI distance from Lao PDR

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Inertial Navigation Gyroscopes are useful when loss of satellites Typically can lose 5-20% of your data but depends on location

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Also Useful to Collect Videologs

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Lao Peoples Democratic Republic Laos the Country –South East Asia –236,800 sq km –Pop. ~5.5 Million National & Provincial Roads –15,600 km –3,600 paved

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company The Project Component of WB Third Highway Improvement Project Survey of All National and Provincial Roads including: –One location reference point survey (LRS) –Road roughness survey (IRI) –Visual assessment of surface integrity (SII) –Inventory (surface type, width, bridges) –Digital photos of the start of links –GPS record of the road centreline Contract Sum US$208,000

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Used Garmin - Appropriate Accuracy for Project Two hour 100% within ±22m, 85% within ±10m without differential correction Extreme terrain impaired satellite availability (PDOP) for < 5-10% of survey No gyroscope or differential correction obtained maps for 100% of network –95% spatial to ±20m –5% spatial to ±20-300m

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Appropriate Accuracy Same Road surveyed by different teams 3 weeks apart 0m 100m System recorded point every second. Post-processed to one point approximately every 10m

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company The Survey Teams Four locally staffed survey teams Completed 14,000 km in 8 weeks Ex-pat training 3 staff per vehicle –Driver –Computer Operator –Condition Assessor –(plus up to 4 observers) “Support” vehicles in Special Zones

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Not all Plain Sailing Time-out on one of the “support” vehicles used through the Special Zones Roads often became impassable with rain

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Ministry Now Have Thematic Mapping Capability

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Thematic Mapping Capability...

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company And Location Referencing

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Now know Where and How Much road they have

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Unexpected Delays: the Photo that Carried a 2-day Sentence... Vietnam Border Post

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Outcomes of Project Using low-cost technology a centreline was established for the entire country Additional data on pavement type and condition collected at the same time Local teams used for data collection - successful transfer of technology Data now in use by consultants, Ministry and World Bank.

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Samoa South Pacific 5,000 sq km Pop. ~ 80,000 ~ 850 km of roads

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company The Project Part of Samoa Asset Management System project Funded by World Bank Centreline survey conducted to: –establish the extent of the network –identify nodes and location reference points –create videolog of roads Contract $USD 20,000

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Equipment Used Trimble Pro-XRS Differentially corrected using base station established for project Data overlaid onto aerial photographs

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Example of Results

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company The Problem Aerial photos and centreline data didn’t match!

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Systematic Difference Data shifted 13 m E/W; 4 m N/S

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Possible Sources of Error ROMDAS Data Processing: –There was an error in the processing of the ROMDAS data. –Eliminated by testing process against data collected and aerial photos for city in NZ Position of Base Station: –There was an error in the position of the base station. –Took average position over 12 days, measurements within 1 m

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Likely Source of Error... Projections: –The two sets of data were prepared using different projection parameters when converting to WSIG. Aerial Photograph Rectification: –There was an error in the rectification of the aerial photographs.

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Impact of Projections and Software for Base Station Location

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Implications Trimble Pathfinder Office gave closest results for projections Appears that aerial photos were incorrectly projected or rectified Subsequent investigations showed that the national grid has errors up to +100 m Solution (temporary!): processed data using Trimble, moving position of base station by 4/13 m.

HTC Infrastructure Management Specialists; a Montgomery Watson Harza Company Conclusions Centreline surveys are an important management tool for road agencies in developing countries Low cost technology makes it possible for any country to collect the data Need to come up with improved procedures for projections and reconciling with existing data sources