Politeknik Ungku Omar

UTILITY MAPPING (UDS) INSTRUMENT

2.1 Understand the instruments used for control survey2.1.1 List the instruments used for the control surveya. Total Station Instrumentsb. Global Positioning System (GPS)

2.2 Understand the instruments used for utilities survey2.2.1 Explain the Pipe and Cable Locator (PCL) instruments2.2.2 Explain the Ground Penetrating Radar (GPR) instruments

2.3 Understand the calibration of detector utility survey2.3.1 Explain the calibration of detector utility survey

instrument

The tools and methods of locating buried utilities are quite diverseAlat dan kaedah untuk mencari utiliti yang ditanam adalah

agak pelbagai.

GPR can be a powerful tool for mapping the location and depth of metallic, non-metallic, plastic, concrete and asbestos-concrete utilities

•Mapping with GPR to systematically cover an area can quickly reveal the distribution and character of multiple buried utilitiesPemetaan dengan menggunakan GPR adalah amat sistematik untuk mengawasi kawasan dengan cepat dan boleh mendedahkan arah saluran serta jenis karakter utiliti yang ditanam.

Why Use GPR for Utility Mapping

For non-metallic element or broken connection of electric current, GPR provide alternative approach.

GPR using radio wave signal to transmitting to ground without any limitation on type of soil and depth (range 1-15 meter for utility mapping)

Common practise to locating buried utilities is energising metal pipes and cables with electric current and using magnetic fields sensor as per Pipe Cable Locator (PCL)

NOGGIN GPR Equipment

Noggin 100 MHz

Noggin 250 MHz

Noggin 500 MHz

Noggin 1000 MHz

NOGGIN GPR Equipment

Noggin 100 MHz

Common Application Geologic mapping and geotechnical applications Deep buried utility locating

NOGGIN GPR Equipment

NOGGIN GPR Equipment

Noggin 250 MHz

Common Application Buried utility locating Archeology Forensic

NOGGIN GPR Equipment

NOGGIN GPR Equipment

Noggin 500 MHz

Common Application Shallow Utility Locating Archeology Forensic

NOGGIN GPR Equipment

Noggin 1000 MHz

Common Application Concrete & Pavement infrastructure assessment: road, pavement, concrete Military UXO and Security Forensics and Archaeology

• Connect the other end of the display cable to the sensor. Ensure the cable is routed

correctly; above the lower cross arm on the cart handle and under the battery tray.

• Attach the odometer cable to the sensor

• Attach the battery cable to the sensor and the battery. The upper red light on the

display unit will illuminate indicating that there is power available for the system.

The system is now ready to use

Start UpPress any button on the display unit (DVL) to turn the system on.

Locate

Press and push.

Use to change Language, Units, Scale, Date, Time and Power Off the system.

To access them during data collection, press the Pause (||) button. Use to change Color, Gain, Depth and turn Filter On and Off. Press Quit to access System Settings.

GPR – geophysical imaging technique for subsurface mapping

RADAR - an acronym coined in 1923 for Radio Detection and Ranging

The most available system commercially is the impulse GPR system.

Ground Penetrating Radar (GPR)Ground Penetrating Radar (GPR)

All GPR units consist of three main components: a power supply, control unit and antenna. To understand how these components interact, we must first understand the definition of a scan. A scan is performed by moving the antenna across the surface linearly to create a series of electromagnetic pulses over a given area. During a scan, the control unit produces and regulates a pulse of radar energy, which is amplified and transmitted into the subsurface at a specific frequency by the antenna. Antenna frequency is inversely proportional to penetration depth, which makes antenna selection the most important step in the survey design process

GPR is a method developed for shallow, high-resolution, subsurface

investigations of the earth. GPR uses high frequency pulsed electromagneticwaves (from 25 MHz to 2,000 MHz) to acquire subsurface information.

G P R Principle

Ground Penetrating Radar (GPR)Ground Penetrating Radar (GPR)

Position of the antenna

Antenna

Del

ay t

ime

Ground Penetrating Radar (GPR)Ground Penetrating Radar (GPR)

Depth, range and resolution depends on factors below:

◦ Radar frequency High freq. good for shallow(700 MHz ~ 2 m ~ min. target

size of 1 cm) Low freq. good for deep (250 MHz ~6 m ~ min. target

size of 5 cm)

◦ Transmitted power◦ medium electromagnetic

properties – how conductive?◦ Shape and characteristic of

target

Ground Penetrating Radar (GPR)Ground Penetrating Radar (GPR)

Sensor Frekuensi Depth

Frekuensi Tinggi > 1000 MHz < 0.5 m

FrekuensiSederhana Tinggi

400 – 600 MHz 0.5 m – 1.5 m

Frekuensi Sederhana Rendah

200 – 400 MHz 1.5 m – 2.0 m

Frekuensi Rendah < 200 MHz 2.0 m – 3.0 m

Depth Vs FrequencyDepth Vs Frequency

http://undergroundsurveying.com/technology/ground-penetrating-radar-gpr/

A table showing various antenna frequencies and their corresponding depth ranges is shown below

Methodology for Using GPR to Locate Buried Utilities

Cross and Mark

Longitude Tracking

Imaging

Methodology for Using GPR to Locate Buried Utilities

Cross and Mark

Most common and very similar method

GPR sensor is moved along sweeps perpendicular to the anticipated utility axis

Methodology for Using GPR to Locate Buried Utilities

Cross and Mark GPR sensor is moved along sweeps perpendicular to the anticipated

utility axis

Figure 1

Methodology for Using GPR to Locate Buried Utilities

Cross and Mark The typical GPR response of a buried pipe or cable is an inverted V

shape The apex of the V indicates the object location. Marking the ground at X location defines the point where the GPR

crosses the utility

Figure 2

Methodology for Using GPR to Locate Buried Utilities

Cross and Mark Implementation at site

No.4 Line was a Storm Drain Location

No.1, 2 & 3 Line is a GPR tracking line

Figure 3

Methodology for Using GPR to Locate Buried Utilities

Cross and Mark Actual image display in Digital Video Line (DVL) These transects shown which were part of the sweeps to locate the pipe. The pipe axis and X’s are marked in Diagram below.

Figure 4

Methodology for Using GPR to Locate Buried Utilities

Longitudinal TrackingApproach is use to look for unusual or changed in buried utility character along the utility path.

Helping in identify changes in depth, potential break, junctions, changes in

construction or leaks depending on the utility type and environmental setting.

A longitudinal tracking usually follows a cross and mark sequence. The GPR is moved along directly over the utility by traversing a line that joins the surface markings as depicted in Figure below

The buried utility alignment need to be define, surveying along the alignment (i.e. joint the X’s) can yield detailed construction information.

Figure 5

Methodology for Using GPR to Locate Buried Utilities

Longitudinal Tracking GPR Profile along Line 4 (in Figure 3) following the Storm Drain

alignment defined by the data in Figure 6.

The Pipe slope and diameter can be determined

Figure 6

Del

ay T

ime

Position of the antenna

Ground Penetrating Radar (GPR)Ground Penetrating Radar (GPR)

impulse GPR works by sending electromagnetic energy in very short pulse into the ground.

Reflected signal captured by the receiver after hitting an object in the ground is process to produce a hyperbolic image.

Depth is obtained from the calibrated radar two way travel time between the transmitter and the utility

Ground Penetrating Radar (GPR)Ground Penetrating Radar (GPR)

Methodology for Using GPR to Locate Buried Utilities

Imaging

Figure 8

Testimonial Site : Site of complex subsurface condition GPR Grid established in the area

Methodology for Using GPR to Locate Buried Utilities

Imaging Merging all the data to create a volume image, slice maps at different depth make long linear consistent transect-to-transect features readily visible

Figure 9

Methodology for Using GPR to Locate Buried Utilities

Imaging For site condition where’s there is no information what is buried or the ground condition are complicated, Imaging approach is the best of addressing these changing conditions. In an imaging survey, data collected over an area on rectilinear grid of lines such as depicted in Figure 7

Figure 7

Methodology for Using GPR to Locate Buried Utilities

Imaging

Figure 10

Depth slices at 0.5 m and 1.1 m for the grid survey The line feature at Y ˜ 2.5 m to 3m is a buried electrical power cable feeding the light standards The feature at 12.5 m is a water sprinkler line. The feature at Y ˜ 7.5 to 10 m in the 1.1 m slice is a concrete storm drain

Methodology for Using GPR to Locate Buried Utilities

PositioningIn some instances, the coordinates of subsurface features are needed to allow adding the located facility to maps and database for future access. The several ways of achieving positioning: Using traditional land surveying via total station Using GPS Survey

Modern GPR system allow integration of the GPR data with all these types of positioning system.

Methodology for Using GPR to Locate Buried Utilities

PositioningA GPS configured system is shown in Figure 11.

The key factors determining the method to employ are cost, accuracy required and efficiency of use

Figure 11

Methodology for Using GPR to Locate Buried Utilities

Summary

GPR provides a powerful utility mapping method.

Ability to use the method depends on a good grounding in the basic principles, common sense, and experience. What appears complex and intimidating becomes simple and routine with a little practice