getting on the map: underground utility location and municipalities by: michael l. gill, pe, rls
TRANSCRIPT
Getting on the Map:Underground Utility Location And Municipalities
By: Michael L. Gill, PE, RLS
Project: Capstone project for Masters in GIS – Penn State
University Dr Doug Miller – Academic Advisor Dr. Sunil K. Sinha – Technical Advisor
To investigate various methods to input municipal underground utility locations into a GIS.
Determine the accuracy of the input methods. Begin to develop a Best Practices for getting
legacy data into a GIS.
The Problem:
How will we get this mapped accurately?
What we do not see - is the problem!
Every time we dig or need to dig, the problem re-occurs!
Problem Statement: Municipal utility employees do not know
where the facilities are located. Municipal utility employees need to know
where their facilities are located. How can the legacy data be transformed into
a modern GIS?
Extent of the problem: In 2005, in Illinois alone
1.22 million “one call” requests Involved 1,700 separate utilities 7.94 million potential conflicts
Consequences of problem: Disruption of utility service Consumer inconvenience Delays in construction Added cost of construction Added utility cost Worker injury Worker death
Results of Poor Mapping:
Current utility data location :
Paper Maps
CADD files
Mental knowledge
GIS input methods:
Heads-up digitizing Scanning CADD Drawings
CADD to GIS file conversion
Traditional location methods: Soil borings Test pits Excavation
Hand Machine
Potholes Vacuum Water jet
New location technologies: Ground Penetrating Radar (GPR) Magnetic field-based location systems Buried markers Acoustic-based plastic pipe locators Could these technologies be directly outputted into a GIS?
GPR unit & print out
It’s in – but how accurate is it?
Can we safely dig wherewe need to?
One-call system accuracy requirements range from12 to 24 inches
Positional accuracy determination: Get features into a GIS
Calculate coordinates Choose a random sample of features Determine “true” position with a more accurate procedure
Use GPS methodology Complete a quantitative comparison of coordinates
Do the math (avg, std dev, range, etc) Understand how the accuracy affects the utility and its
location procedures
Research Methods Capturing Institutional Knowledge
Operators digitize fire hydrant and sanitary sewer manhole locations into a GIS (ArcMap)
Professional Survey Crew GPS’s same point locations (determine “true” location)
Compute locations discrepancies (error distances) for various variables
Research Results -Albion
Fire Hydrants – 6-in Base
n 10
Min 1.8
Max 23.2
Mean 8.6
Std Dev 7.7
GPS Unit - Trimble 5700 with base stationAccuracy 5 -10 mmBase Map: 1m & 6-in Resolution
Manholes - 6-in Base
n 26
Min 0.2
Max 23.9
Mean 11.9
Std Dev10 10.1
Research Results - AlbionFire Hydrants – 1m Base
n 2
Min 7.2
Max 8.6
Mean 7.9
Std Dev 4.8
Manholes – 1m Base
n 2
Min 11.2
Max 20.9
Mean 16.1
Std Dev 4.8
Fire Hydrants – All Data
n 12
Min 1.8
Max 23.2
Mean 8.5
Std Dev 7.1
Manholes – All Data
n 28
Min 0.2
36.9 23.2
Mean 12.2
Std Dev 9.9
Research Results - Grayville
Fire Hydrants – 6-in Base
n 5
Min 2.2
Max 9.8
Mean 5.8
Std Dev 2.6
GPS Unit - Trimble 5700 RoverAccuracy 1-3 mBase Map: 1m & 6-in Resolution
Manholes – 6-in Base
n 14
Min 4.3
Max 68.2
Mean 23.8
Std Dev 19.0
Research Results - GrayvilleFire Hydrants – 1m Base
n 16
Min 6.3
Max 52.8
Mean 24.9
Std Dev 13.6
Manholes - 1m Base
n 24
Min 2.5
Max 89.1
Mean 24.9
Std Dev 17.5
Fire Hydrants – All Data
n 21
Min 2.2
Max 52.8
Mean 20.3
14.4 2.6
Manholes – All Data
n 38
Min 2.5
Max 89.1
Mean 24.5
Std Dev 18.1
Research Results - Lawrenceville
Fire Hydrants
n 13
Min 3.8
Max 37.7
Mean 10.2
Std Dev 8.6
GPS Unit – Thales Mobile Mapper CEAccuracy Sub-meterBase Map: 1m Resolution
Fire Hydrants – with Beacon Pack
n 13
Min 0.1
Max 37.6
Mean 10.2
Std Dev 8.6
Research Method - Georeferencing This part not finished!
Breaking the cycle: GPS both horizontal and vertical positions of
underground utilities when: New construction takes place During maintenance operations Fixing breaks Anytime facility is exposed
Use data to update and improve the accuracy of existing maps.
Goals Get all underground utilities mapped into a
modern GIS system Have mapped data accuracies to within “one-
call” system tolerances Capture and map vertical data as well as
horizontal data
Proposed Location Capture Standards Existing Systems
GPS all valves, and meters (after digitizing) Adjust digitized lines to match GPS points
These surface features are directly above underground facilities
Proposed Location Capture Standards GPS all lines, fittings etc anytime they are
exposed of maintenance, locates, repair, construction, erosion or any other reason Adjust digitized lines to match GPS points
New Systems or Construction Urban
Capture both horizontal and vertical data to sub-foot location tolerances
Capture location points at all fittings, valves, meters services, etc.
Capture line locations at a maximum line spacing of 100 feet
Keep GIS mapping up to date
New Systems or Construction Rural
Capture both horizontal and vertical data to sub-foot location tolerances
Capture location points at all fittings, valves, meters services, etc.
Capture line locations at maximum spacing of 500 feet
Keep GIS mapping up to date
Idea to Ponder Should location capture standards be a
requirement the same as pipe material, pressures, etc?
Assumptions & Limitations: Small sample set Local in scope GPS data is more accurate than input methods
Thank you!Questions?