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?