Survey Specifications

SURVEY
SPECIFICATIONS

Presented by S A Strydom

Table of Contents

1. INTRODUCTION………………………………………………………………………………………………………… 2
   
2. WHAT IS SURVEY?…………………………………………………………………………………………………….. 2
   
3. WHAT IS THE ROLE OF THE SURVEY PROFESSION?…………………………………………………. 3
   • Survey related costs………………………………………………………………………………………………………… 3
     
4. WHICH ACTS CONTROL THE SURVEY PROFESSION?………………………………………………… 3
   • The professional and technical surveyors Act 40 of 1984, soon to be replaced by The Geomatics Professions Act 19 of 2013………3
   • The Land Survey Act 8 of 1997…………………………………………………………………………..5
     
5. WHY A SURVEY SPECIFICATION?………………………………………………………………………………. 5
   • Root of the Problem……………………………………………………………………………………………………….. 5
   • Inadequate survey specifications lead to……………………………………………………………………………….. 5
   • Survey and Mapping Requirements……………………………………………………………………………………… 6
   • Survey standards/Inadequate Specification / Common Mistakes / Watch Out For………………………………. 8
     
6. ESSENTIAL ELEMENTS OF A SURVEY SPECIFICATION…………………………………………….. 12
   • Description of project…………………………………………………………………………………………………….. 12
   • Qualifications of surveyor……………………………………………………………………………………………….. 13
   • Specify accuracies and equipment……………………………………………………………………………………… 13
   • Specify Health and Safety requirements………………………………………………………………………………. 14
   • Specify induction requirements………………………………………………………………………………………… 15
   • Payment proposal………………………………………………………………………………………………………… 15
   • Bill of quantities…………………………………………………………………………………………………………… 15
   • Survey control……………………………………………………………………………………………………………… 17
   • Survey……………………………………………………………………………………………………………… 18
     
7. DELIVERABLES………………………………………………………………………………………………………… 18
   • Survey records…………………………………………………………………………………………………………….. 18
   • Survey report………………………………………………………………………………………………………………. 19
   • Accommodation…………………………………………………………………………………………………………… 19
   • Vehicles……………………………………………………………………………………………………19
     
8. SURVEY INSTRUMENTS AND ACCURACIES……………………………………………………………… 19
   
9. WEBSITES AND REFERENCES………………………………………………………………………………….. 20
   
10. READING MATERIAL……………………………………………………………………………………………. 20
    
11. TYPICAL BILL OF QUANTITIES…………………………………………………………………………… 21

HOW DO YOU COLLECT THE SPATIAL INFORMATION TO GET

SURVEY SPECIFICATION WORKSHOP

INTRODUCTION

Engineers, project managers, architects, planners and various other professionals all need up-to-date spatial data for decision-making, design and construction purposes.

A registered Geomatician is the person qualified to do this. This can be a surveyor (cadastral, engineering, mining), photogrammatrist, hydrographer and GIS Professional.

2. WHAT IS SURVEY?

In its broadest sense, the term surveying encompasses all activities that measure and record information about the physical world and the environment. The term is often used interchangeably with geomatics which is the science of determining the position of points on, above or below the surface of the earth.

Survey is present in all facets of construction. From feasibility study, planning, survey, design, construct, built to maintain.

3. WHAT IS THE ROLE OF THE SURVEY PROFESSION?

To measure the natural environment and represent it in a mathematical environment.

This includes but is not comprehensive inter alia:

• To create and identify property and determine what real rights (servitudes, mining rights, proclamations, future planning) affect the property and define the boundaries of the cadastral parcel of land affected.
• To supply accurate data from below, on and above the ground for design purposes.
• To assist the construction process by setting out and monitoring of civil works and structures.
• To supply up to date as-built plans after construction.

3.1 – Survey related costs

Survey is one of the professions with the highest entry level cost –

• To qualify – R600 000 plus
• Equipment + software – R800 000 basic but can be up to R3 000 000
• Survey fees are minimal – Usually not more than 0.0015% of project value

4. WHICH ACTS CONTROL THE SURVEY PROFESSION?

The survey profession is governed by two acts being:

4.1 The professional and technical surveyors Act 40 of 1984, soon to be replaced by The Geomatics Professions Act 19 of 2013

In terms of this Act there are different categories of surveyors who must be registered with the South African Council for Professional and Technical surveyors (PLATO) before they can practice as surveyors and GIS practitioners. To find information regarding survey, visit www.plato.org.za. The names of all registered surveyors and GIS professionals are listed on this site.

The different categories of surveyors are:

In South Africa there are three tertiary qualifications being a degree (B Sc survey, B Tech survey) and a diploma (N Dip survey).

4.1.1 Cadastrall

• Professional Srveyor (PLS) – B Sc (Survey)

Once registered this person is qualified to run his/her own practice. Professional Land Surveyors are legally responsible for all surveys involving boundaries and land title. No other survey category is allowed to do this work. In addition to this a PLS can contract for any other survey work including engineering and aerial surveys.

They are also involved in planning, project development and professional consultation.

• Professional Surveyor in Training (PLST) – B Sc (Survey)

This person is not qualified. A person becomes a professional surveyor in training after obtaining the degree in surveying at a South African university, or its equivalent as certified by the South African Council for Professional and Technical Surveyors (PLATO). After extensive prescribed training and writing of a PLATO law examination in land related laws, the candidate may apply for registration as a Professional Surveyor (PLS).

4.1.2 Engineering Surveyor Categories (Technologists) – N Dip (Survey) and B Tech (Survey)

Engineering Surveyors are not allowed to execute cadastral surveys but perform all other surveys related to engineering and construction work such as surveys necessary to control, set out and monitor the construction of buildings, roads, bridges, dams, etc. The work is varied and often requires high responsibility.

• Professional Engineering Surveyor (PS) – B Tech (Survey)

This person is qualified to run his own practice. A Professional Engineering Surveyor must first register as an Engineering Surveyor and after completing the training as prescribed apply for registration as a Professional Engineering Surveyor. The person must do prescribed work integrated learning and also write the necessary law examinations before he/she can apply for registration with PLATO.

• Engineering Surveyor (S) – N Dip (Survey) or B Tech (Survey)

This person is qualified to run his own practice. After being registered as an Engineering Survey Technician and acquiring a minimum of three (3) years approved practical experience, a candidate may apply to be registered as an Engineering Surveyor.

• Engineering Survey Technician (ST) – N Dip (Survey) or B Tech (Survey)

This person is not qualified to run his own practice and may only work under the personal supervision of a suitably qualified person. This is the status of a person that acquired his/her degree or diploma but who cannot register yet.

• Engineering Survey Technician-in-Training (STT) – No academic requirements

This person is not qualified to run his own practice and must work under supervision of a registered Professional Surveyor.

There are no academic or technical requirements for registration as an Engineering Survey Technician-in-Training.

It is normal to register as an Engineering Survey Technician-in-Training when commencing studies at a University of Technology.

Note: The abbreviations PLS / PS / S etc. indicate the prefix to the registration number of the particular individual and can be used as guideline to determine whether the person is qualified to do a specific type of survey.

4.2 The Land Survey Act 8 of 1997

The purpose of this act is to regulate the survey of land which includes all real rights such as property boundaries, mineral and mining rights, servitudes, sectional title, leases and any other real right that needs to be registered in the deeds office or mining titles office.

Only a registered Professional land surveyor is allowed to execute cadastral surveys.

5 WHY A SURVEY SPECIFICATION?

Before design and construction can commence, the person who needs the information must know what the design perimeters and tolerances are. The surveyor must ensure that the data supplied is of an accuracy and information standard where the client can design within the required perimeters and tolerances.

5.1 Root of the Problem

Consultants writing survey and mapping specifications do not always understand:

• Requirements of client
• Different types of survey equipment and their accuracy specifications
• The survey process
• Accuracies that are required for design and mapping

5.2 Inadequate survey specifications lead to:

1. Clients receiving a product that do not answer to their expectations
2. Disputes
3. Big variation in fees
4. Time wasted by both surveyor and consultant to clarify the specification after survey
5. Plans and data do not overlay and does not represent the true situation on the ground
6. The survey was not executed to the accuracy required for design
7. Volumes are incorrect due to different dates on site
8. Plant equipment do not fit or tie in
9. There are disputes with contractors regarding volumes

5.3 Survey and Mapping Requirements

Each phase of the construction process has different survey & mapping requirements i.e.:

Typical Greenfields Project

• FEL(Front –end Loading) 1 Identification/Pre-Feasibility Study / Exploration
  • Satellite Images
    • Aerial SurveyGround SurveyCadastral Survey
    FEL 2 Evaluate/Feasibility Study/Preliminary design
    • Ground Survey, Higher Accuracy Aerial or Lidar Survey
    FEL 3 Project Planning/Define/Design
    • Ground Survey, Higher Accuracy Aerial or Lidar Survey
    FEL 4 Execute/Construction
    • Ground Survey
  • FEL 5 Operate/Post construction
    • As-built Survey/Maintain/Manage/BIM

Typical Brownfields Project

• Existing Plant
• Overhead / Underground Services
• Services Corridors to Plant
  • Roads
  • Powerlines
  • Pipelines

5.4 Survey standards/Inadequate Specification / Common Mistakes / Watch Out For

• Survey Regulations

The survey regulations promulgated in terms of the Survey Act control the way in which survey work is conducted in South Africa and it also specify how surveys need to be executed – www.plato.org.za

• Department of National Geo-Spatial Information: http://www.ngi.gov.za/

The department has a comprehensive list of survey standards and it will be helpful especially if large area survey specifications need to be executed.

• TMH 11(Technical methods for highways)

Please note that TMH 11 is not n survey specification for general surveys. It is the SANRAL specification for road surveys and very comprehensive.

It is a very comprehensive specifications list detailing things like cadastral calculations, benchmark build and survey standards, aerial photography annotation etc. This could make survey unnecessarily expensive. The engineer should only specify applicable sections

The best is to specify which part of TMH 11 is relevant.

• National Co-Ordinate Systems

Different countries have different survey systems / projections. Normally there is a big difference between the local system and WGS 84.

If a surveyor has to survey long baselines(more than 50 km) or cross border surveys the engineer must ensure(ask for proof) that the surveyor knows how to do this.

• Local Co-ordinate systems

There is big confusion between the use of National survey system and local on site survey system for construction.

A local system on site on site has the following qualities:

• The output data set reflects displacements and not co-ordinates
• The system can be orientated to suit a particular reference line
• The co-ordinates must be “true”on site level.

5.4.2 Software

Software does not always calculate conversions accurately.

5.4.3 Watch Out For

• Chief Directorate Contours or scanned images especially contours.

These contours were produced via scanning and/or high altitude flying. It is good enough for information purposes but not for design. Height accuracies can be up to 20 m incorrect.

• Trigonometrical Beacons and Bench marks on site

In built up areas and construction sites these beacons can be moved, bumped or replaced. You cannot trust data of a survey that is connected to one beacon only. When working on a construction site it is advisable to calibrate daily.

5.4.4 Google Earth

Google earth can only be used for information purposes.

Relative x, y accuracies can vary from 2m to 50 m or more and absolute accuracies up to km.

Heights and contours can be out by up to 40m.

Please note that you are most probably encroaching on copy right principles if you use google for design.

5.4.5 Survey techniques

• Height determination

Spirit Levelling: This is the one of the most important actions to determine height and you must specify double(check) levelling and part of the survey report is to proof that it was done

GPS Levelling: Over long distances where bench marks are more than 5 km apart it is possible to achieve the same accuracy or better than with spirit levelling.

NB Special techniques need to be used to do this and there are very few surveyors who can do this. See attached article by W Mulder.

• Double polar

It is standard practise to place a beacon from one benchmark and check it from another.

• Closed traverse

It is standard practise to start a survey on a known point (BM) and close the survey on a known point.

• Number of points surveyed to generate contours

Keep in mind that you must specify the density of points surveyed and not the contour interval

Example:

Survey of points at 20 m intervals = 25 pts per Ha (Walk about 600 m) Survey of points at 10 m intervals = 100 pts per Ha (Walk about 1100m)

It obvious that the person surveying a point every 10 m will be much more expensive than the person surveying point every 25m

• GPS and levelling HeightsEllipsoid – Mathematical figure of the earth.

• Geoid-The geoid is a model of global mean sea level that is used to measure precise surface elevations
  
• Geoid Ellipsoid Separation

Measurements made on the earth with conventional survey instruments will follow along the shape of the geoid.

Instruments using satellites refer all measurements, including heights, directly to the ellipsoid.

6. ESSENTIAL ELEMENTS OF A SURVEY SPECIFICATION

6.1 Description of project

It is important to state the following regarding the project

• Project description – Clearly state the purpose of the survey

• Clearly state the extent of the survey e g 2000Ha or strip survey X Km long and Ym wide. On larger projects it is essential to supply existing plans and data as part of the survey brief.

If nothing is available then it is still necessary to supply some quantities in order to be able to compare apples with apples.

• Where – The project might be outside South Africa and then there will be factors such as visas and work permits.
• Completion date/duration – This is important especially on large projects. The survey concern must know whether more than one survey team will be needed.

6.2 Qualifications of surveyor

As per Par 4 above there are various categories of surveyors and it is important to appoint the person that is appropriately qualified. It is not good enough to state that the surveyor must have suitable experience.

6.3 Specify accuracies and equipment

It is very important to specify accuracies that need to be achieved because there are numerous types of equipment and survey methodologies that can be applied.

In order to do this the person using the data must know what design tolerances he needs.

Discuss different accuracies between preliminary design, civil works design, monitoring, high rise buildings, structural and refurbishment of plant.

6.3.1 Confidence level and accuracy

The probability that the value of a parameter falls within a specified range of values.

• Relative and absolute accuracy
• Absolute Accuracy

The degree to which the position of an object on a map conforms to its correct location on the earth according to an accepted coordinate system.

• Relative Accuracy

A measure of positional consistency between a data point and other, near data points. Relative accuracy compares the scaled distance of objects on a map with the same measured distance on the ground.

• RMS

The root-mean-square deviation (RMSD) or root-mean-square error (RMSE) is a frequently used measure of the differences between values predicted by a model or an estimator and the values actually observed. Basically, the RMSD represents the sample standard deviation of the differences between predicted values and observed values. These individual differences are called residuals when the calculations are performed over the data sample that was used for estimation, and are called prediction errors when computed out-of-sample.

• Standard Deviation

Dark blue is less than one standard deviation from the mean. For the normal distribution, this accounts for 68.27% of the set; while two standard deviations from the mean (medium and dark blue) account for 95.45%; and three standard deviations (light, medium, and dark blue) account for 99.73%.

In statistics, the 68–95–99.7 rule, also known as the three-sigma rule or empirical rule, states that nearly all values lie within three standard deviations of the mean in a normal distribution.

68.27% of the values lie within one standard deviation of the mean. Similarly, 95.45% of the values lie within two standard deviations of the mean. Nearly all (99.73%) of the values lie within three standard deviations of the mean.

• Areas of uncertainty for overlaying of data
  • Integration of data from different sources and in different formats at different scales will result in a questionable product.
  • The highest accuracy that can be expected is only as accurate as the least accurate data set imported.
  • Never extrapolate scale.

6.4 Specify Health and Safety requirements

Notwithstanding our expectation to work in a risk-free environment, accidents happen, causing injuries illnesses and death

An employer has legal and moral obligations to safeguard all employees, suppliers, clients and the public against injury and disease, as well as risks to health and safety, from all operations associated with its business

Failure to do so could lead to prosecution

6.4.1 The main features of Safety, Health and Environment Legislation are:

• Regulating health and hygiene
• Duty to provide H&S training to employees
• Election of H&S representatives
• Duty to take all possible steps to prevent an incident, in addition to taking corrective action after an accident has occurred
• Severe penalties for failing to maintain a healthy and safe workplace
• Requirement to have a formalised risk assessment and management programme
• Liability of suppliers of articles and service providers (contractors), used by the company

6.4.2 Where does the SHE Legislation apply

SHE Legislation applies as a general rule in all employment activity and machinery usage. This provides for a very wide field of application. Therefore legislation regulates safety, health and environmental requirements pertaining to workplaces ranging from mines to residential homes.

Health and safety is an important part of any project and the health and safety requirements has an effect on costs. The engineer must ascertain from the client what the requirements are and clearly state it in the survey brief. Pay special attention to equipment, vehicles, safety gear and medical certificates.

Examples where health and safety is applicable – railway lines, roads, electrical powerlines, even in the field 70% of surveyors have been hi-jacked or equipment stolen on site

6.5 Specify induction requirements

Before entering large construction sites or plant areas it is necessary to do induction. This can take anything from 2 hours to 3 weeks and quite often involves travelling or special courses. Specify clearly

6.6 Payment proposal

Clearly state the payment schedule. This is very important because the surveyor is normally one of the first persons on site and his costs are very high especially away from base. It is not fair to expect him to wait for his money until the engineer is paid. It is fair to pay his mobilisation and induction fees up front. A further payment when all field work is completed and then when all the work is completed.

6.7 Bill of quantities

During this session all aspects of a survey project will be discussed and examples of each facet will be supplied.

A bill of quantities is the most appropriate way to obtain the best comparative price for a survey.

6.7.1 Mobilization

The surveyor must know the distance to the terrain and whether there is accommodation on site or whether daily traveling to site is necessary.

6.7.2 Survey system

For a comprehensive description of the South African system go to –

http://www.ngi.gov.za/index.php/technical-information/geodesy-and-gps/datum-s-and- coordinate-systems

There are various survey systems in the world and it is very important to know what system to work in, especially when working in foreign countries. UTM, Lo, WGS 84 are common names that crop up. Please note that WGS 84 is not a survey system but a mathematical form of the earth.

Most countries do have a Network of Trigonometrical beacons which is linked to the national map datum.

6.7.3 Map Projection

For comprehensive information visit –

http://www.ngi.gov.za/index.php/technical-information/geodesy-and-gps/datum-s-and- coordinate-systems

• South Africa: Gauss Conformal Projection. Previously known as Lo and since 1999 Hartebeesthoek 94 Datum or WG 94
  
• Africa: Most African Countries work on Universal Transverse Mercator (UTM)

6.7.4 Ellipsoid Definition:

Common names of systems on maps are Clarke 1880, Clarke 1886 and WGS 84.

WGS84: Most modern surveys are based on the WGS84 ellipsoid. This is a mathematical form of the earth. There are older systems which you might come across e.g. Clarke 1880 or 1886. GPS navigation is based on WGS 84 and therefor most surveys use this as reference ellipsoid but it is still necessary to connect to the local survey system for the site.

Local systems: It is very important to know that construction sites normally work on a local system or “flat” grid. Please ask a professional surveyor to specify the system to work in. There is a scale factor between systems that can lead to errors in construction.

Clearly specify which system must be used.

6.8 Survey control

Benchmarks are the backbone of any construction site whether it is a small or large terrain. It must clearly be stated how many benchmarks are needed. A minimum of 3 inter-visible BM’s are required. Since the development of modern equipment e.g. GPS and Lidar it is not necessary for benchmarks to be inter-visible but there must be enough on site for setting out to be possible when construction commences. The maximum reach length of real time GPS is about 5 km but in dense bush it can be 2 km. There are other considerations for aerial survey and there bench marks can be 30 km apart. It is therefore important for the engineer to know what he/she wants out of the survey. Ask a professional surveyor for advice

• Accuracy: Accuracy of benchmarks is important. A general rule is that the benchmarks should be 3 times more accurate than the survey requirement.
  
• Example: A contour plan with 10 cm accuracy requirement needs a benchmark accuracy of about 3 cm.
  
• Construction: Clearly specify the construction of the benchmark e g 12 mm x 50 mm peg in concrete base of 15mm diameter and 30 mm deep. Keep in mind that you need sturdy benchmarks on construction and mining sites.

Benchmarks are an important but costly part of survey. It is therefore very important to clearly state the number, construction and survey methodology to use for benchmarks.

6.9 Survey

• Fieldwork: It is necessary to clearly specify what you want out of the survey and what detail you need e.g. power lines, clearances, manholes, underground services, fences etc.

In general you can expect the following:

6.9.1 Ground survey:

This can be done by total station or GPS and is generally necessary for detail surveys for design purposes. This is the solution when you need accuracies of 5 cm and better and want all detail.

6.9.2 Airborne Lidar or aerial survey:

This is normally required for larger areas and strip survey for route selection and preliminary design. It is difficult for this methodology to achieve accuracies better than 8 cm

6.9.3 3D survey

Today it is possible to supply high accuracy 3 D plans surveyed with Lidar equipment as well as photogrammetry. This is highly specialised and there are many pitfalls for the in- experienced. It is proposed that this type of specification is drawn up with the help of a professional surveyor and 3D CAD specialist.

Due to the fact that these are normally very high accuracy surveys it is necessary that benchmarks are very accurately surveyed and electronic levelling is essential.

Lidar equipment can be mounted on any vehicle (air, land, water) and therefore it is essential to know what you need and what can go wrong.

• Quality control
  • It is important to state that certain check surveys need to be done to confirm accuracy on the ground. This means that certain points need to be surveyed from bench marks after plan production but from different bench marks than on the original survey. This is very relevant where remote sensing techniques (satellite imagery, airborne and mobile mapping) were used.

7. DELIVERABLES

7.1 Electronic data and plans

Specify the format of plans and data especially if you need hard copy plans. Also state what software is used for design and specify that data must be supplied in that format.

The surveyor should be able to supply the data in any format of your choice. Please clarify this prior to the survey because certain CAD packages require different field procedures.

7.3 Survey records

It is necessary to clearly specify what survey records you need to proof that fieldwork has been done and how the survey was conducted. This may include:

• Fieldbooks, electronic data capturing files and printouts.

• Co-ordinate list with beacon description of all benchmarks and beacons on site.

• Comparison of co-ordinates if this survey is based on a previous survey.

7.3 Survey report

This report is essential. The surveyor must clearly specify how he did the survey, what control was used, how he fixed the control, survey methodology used to survey x y & z and what problems were encountered. It must be written in such a way that the engineer and any person that need to use the survey data can clearly understand how the work was executed.

7.4 Accommodation

Accommodation is important. Keep in mind that survey crews, whether ground or air based consist of anything from 2 to 5 or more persons. Modern equipment needs electricity and dust and damp damage equipment.

7.5 Vehicles

The terrain dictates the type of vehicle to be used. Most ground based survey teams use 4×4 vehicles to cater for all terrains. On construction sites, especially mines and large construction projects there will be a health and safety specification which requires conversions to vehicles. Roll bars in the vehicle, special markings on the vehicle, medical kits, flags and stretchers are all examples of what might be required.

On most construction sites people are not allowed to travel on open vehicles and double cab vehicles might be a requirement.

These requirements must be clearly stated in the specification.

8. SURVEY INSTRUMENTS AND ACCURACIES

• Total Stations: 2mm – 10cm depending on model

• Electronic levels: 1mm – 10mm

• GPS: 2cm to several meter depending on several factors.

• Lidar systems
  • Terrestrial (TLS): 1mm to 10cm depending on model
  • Mobile (MLS): 2cm to 5m depending on model
  • Airborne (TLS): 8cm to 1m depending on several factors

• Remotely Piloted Aircraft (RPA): 8cm to several meter depending on several factors

• Hydrographic-sonar systems: 10 cm to several meter depending on several factors

• Underground services detection: Ground penetrating radar (GPR): 10 cm to 1m depending on several factors.

9.  WEBSITES AND REFERENCES

South African Geomatics Institute: www.sagi.co.za

South African Council for Professional and Technical Surveyors: www.plato.org.za

Chief Surveyor General: www.csg.dla.gov.za

National Geo–Spatial information: http://www.ngi.gov.za/

http://www.gitta.info/MetaDataQual/en/multimedia/PositAccuracy.pdf

http://bgis.sanbi.org/gis-primer/page_08.htm

http://en.wikipedia.org/wiki/Root-mean-square_deviation

http://en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule

10.  READING MATERIAL

The science and art of surveying – Fritz van der Merwe University of Pretoria

Ground control over long distances – Wynand Mulder – AAM Geomatics

Basics of Aerial Survey – Wynand Mulder – AAM Geomatics

Basic Airborne Lidar Survey Specification – S A Strydom

11. TYPICAL BILL OF QUANTITIES