What is the difference between a CAT and a Genny in utility surveying?

A CAT (Cable Avoidance Tool) is a receiver that detects electromagnetic fields from live power cables or signals induced onto metallic pipes. A Genny (Signal Generator) is a transmitter that applies a specific signal to a utility, allowing the CAT to detect it even if it's not live. In practice, you use the Genny to 'energise' a target utility (e.g., a gas pipe) and the CAT to locate it. They are often used together as a 'CAT and Genny' system.

How deep can GPR detect utilities?

The detection depth of GPR depends on the antenna frequency and ground conditions. A 400 MHz antenna typically detects up to 2-3 metres in dry sandy soil, but in wet clay, depth may be less than 1 metre. Lower frequencies (e.g., 200 MHz) can reach deeper (up to 5 metres) but with lower resolution. Always check the manufacturer's specifications and conduct a site calibration.

What is PAS 128 and why is it important?

PAS 128 is a publicly available specification for underground utility detection, verification, and location. It defines four survey types (A, B, C, D) with different levels of accuracy and methodology. Type D is a desktop study only, while Type A is the most comprehensive, involving detection, verification, and precise location. Following PAS 128 ensures consistency, quality, and legal compliance in utility mapping projects.

Do I need to mark utilities on the ground during a survey?

Yes, marking utilities on the ground is a standard practice to provide a visual record for excavation teams. Typically, you use spray paint (e.g., red for electric, yellow for gas, blue for water) following the APWA uniform colour code. Markings should include the utility type, direction, and depth if known. Always photograph the markings before they fade.

What should I do if I find an unmapped utility on site?

First, record its location accurately using GPS or total station, and note its depth, material, and any visible features (e.g., valve covers). Then, inform the site supervisor and update the utility records. In your survey report, clearly mark it as 'unrecorded service found' and recommend further investigation if needed. This is crucial for safety and avoiding future strikes.

How do I avoid interference from adjacent utilities when using EML?

Interference occurs when signals from nearby utilities bleed onto the target. To minimise this, use the Genny's 'power' mode to detect live cables first, then switch to 'radio' mode for other services. When using direct connection, ensure the signal is applied only to the target utility by isolating it (e.g., using a clamp). Also, use the 'peak' and 'null' modes on the CAT to distinguish between multiple signals.

Preparation for Work

PROQUAL AWARDING BODY

vocational

This subtopic focuses on self-assessment of personal attributes against industry requirements and proactive exploration of career pathways within utility mapping and surveying. Learners develop the ability to align their competencies with job roles, fostering employability through targeted research into sector opportunities and progression routes.

Learning Outcomes

Assessment Guidance

Key Skills

Key Terms

Assessment Criteria

Assessment criteria

ProQual Level 2 Diploma in Utility Mapping and Surveying

Topic Overview

The ProQual Level 2 Diploma in Utility Mapping and Surveying is a vocational qualification designed for individuals seeking a career in the utility surveying industry. This diploma covers the fundamental principles of utility mapping, including the detection, identification, and recording of underground utilities such as gas, water, electricity, and telecommunications. Students learn to use electromagnetic locators, ground-penetrating radar (GPR), and other surveying equipment to produce accurate utility maps, which are essential for construction projects to avoid service strikes and ensure safety.

This qualification is part of the Construction & Building Services sector and is recognised by employers and professional bodies like The Survey Association (TSA). It provides a solid foundation for roles such as utility surveyor, mapping technician, or site engineer. The course combines theoretical knowledge with practical skills, covering topics like health and safety regulations (e.g., HSG47), data management, and the interpretation of utility records. By the end of the diploma, students will be competent in conducting site surveys, producing detailed utility drawings, and understanding the legal and environmental considerations of utility mapping.

Utility mapping is critical in modern construction because buried services are often unmapped or inaccurately recorded. The diploma equips students with the skills to reduce risks, prevent costly damage, and improve project efficiency. It also aligns with the UK's drive for digital transformation in infrastructure, as utility mapping data is increasingly integrated into Building Information Modelling (BIM) systems. This qualification opens pathways to further study, such as the Level 3 Diploma in Utility Mapping, or direct employment in surveying companies, utility firms, or local authorities.

Key Concepts

Core ideas you must understand for this topic

→Electromagnetic Location (EML): Using a transmitter and receiver to detect metallic utilities by inducing a signal onto the pipe or cable. Students must understand signal coupling methods (direct connection, induction) and how to avoid interference from adjacent services.
→Ground-Penetrating Radar (GPR): A non-destructive method that uses radar pulses to image the subsurface. Key principles include understanding wave propagation, dielectric permittivity, and how to interpret radargrams to identify non-metallic utilities like plastic pipes.
→Utility Records and Plans: The ability to obtain and interpret existing utility records from statutory undertakers (e.g., via LinesearchbeforeUdig). Students learn to assess the accuracy of records and identify discrepancies during site surveys.
→Surveying Methodology and PAS 128: Following the British Standard PAS 128 for utility detection, verification, and location. This includes categorising surveys into types (e.g., Type A, B, C, D) and understanding the quality levels of data.
→Health and Safety (HSG47): The Health and Safety Executive's guidance on avoiding danger from underground services. Key aspects include risk assessment, safe digging practices, and the use of CAT (Cable Avoidance Tool) and Genny (Signal Generator) correctly.

Learning Objectives

What you need to know and understand

Understand how own skills and qualities relate to those needed for working life; research personal career opportunities

Assessment Criteria

Key criteria assessors look for in your portfolio

Award credit for a comprehensive self-audit mapping personal skills (e.g., technical, communication) to specific competencies required in utility mapping roles.
Credit should be given for thorough research into at least two distinct career paths, detailing entry requirements, typical responsibilities, and progression opportunities.
Evidence must include reflection on personal development areas, with a clear action plan linking current qualifications to career goals.
Assessors should look for use of credible sources (e.g., professional bodies, job market data) to support career research, demonstrating genuine engagement with the sector.

Assessment Guidance

Guidance for achieving higher grades

💡Use real job descriptions from current industry vacancies to benchmark your skills—this shows application of research and contextual understanding.
💡Present findings in a structured format, such as a skills matrix or career development plan, to meet assessment criteria for clarity and depth.
💡When researching careers, explore professional body resources (e.g., CICES, RICS) to demonstrate awareness of industry standards and continuing professional development.
💡In practical assessments, always demonstrate a systematic search pattern (e.g., grid or spiral) when using EML or GPR. Examiners look for methodical coverage of the survey area to ensure no utilities are missed. Rushing or random scanning loses marks.
💡When interpreting utility plans, annotate them clearly with your own observations from the site survey. Show where you agree or disagree with existing records, and explain why (e.g., 'recorded gas main not found – possibly abandoned or rerouted'). This demonstrates critical thinking.
💡For written exams, memorise the key steps in PAS 128 survey types. For example, a Type B survey involves a site reconnaissance and utility record search, but no detection equipment. Be able to justify which survey type is appropriate for a given scenario.

Common Mistakes

Common errors to avoid in your coursework

Superficial self-assessment that lists generic skills without linking them to specific job functions in surveying.
Research limited to a single job title or employer, failing to demonstrate breadth of sector awareness.
Overlooking the importance of soft skills (e.g., teamwork, problem-solving) in utility surveying roles, focusing only on technical abilities.
Misconception: All underground utilities can be detected with a CAT and Genny. Correction: CAT and Genny only detect metallic utilities or those with a tracer wire. Non-metallic pipes (e.g., plastic water mains) require GPR or other methods, and even then, detection is not guaranteed.
Misconception: Utility records from companies are always accurate. Correction: Records are often incomplete or inaccurate due to poor historical mapping, changes over time, or unregistered private services. Always verify records with site surveys and mark-ups.
Misconception: GPR can detect any object at any depth. Correction: GPR performance depends on soil conditions (e.g., clay attenuates signals), frequency of antenna (lower frequency for deeper but lower resolution), and object material. It cannot detect very small or deep objects reliably.

Frequently Asked Questions

Common questions students ask about this topic

Before You Start

Prior knowledge that will help with this topic

•Basic understanding of construction site safety, including risk assessments and method statements (RAMS).
•Familiarity with reading maps and plans, including scale, symbols, and grid references.
•Elementary mathematics for calculating depths, distances, and signal strengths (e.g., using trigonometry for offset measurements).

Key Terminology

Essential terms to know

Understand how own skills and qualities relate to those needed for working life; research personal career opportunities

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Key Concepts & Core Principles

Exam Tips & Revision Strategies

Common Misconceptions & Mistakes to Avoid

Examiner Marking Points

Preparation for Work

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Topic Overview

Key Concepts

Learning Objectives

Assessment Criteria

Assessment Guidance

Common Mistakes

Frequently Asked Questions

What is the difference between a CAT and a Genny in utility surveying?

How deep can GPR detect utilities?

What is PAS 128 and why is it important?

Do I need to mark utilities on the ground during a survey?

What should I do if I find an unmapped utility on site?

How do I avoid interference from adjacent utilities when using EML?

Before You Start

Key Terminology

Ready to learn?

Related Topics in PROQUAL AWARDING BODY vocational Construction & Building Services

Conforming to General Health, Safety and Welfare in the Workplace

Conforming to Productive Working Practices in the Workplace

Installing fire resisting timber doorsets in the workplace

Advanced Concrete Technology and Mix Design