basic survey principles

8/8/2019 Basic Survey Principles

1/11

LOVELY PROFESSIONALUNIVERSITY

TERM PAPER OF SURVEYING

Topic :- PRINCIPLES OF SURVEYING

Submitted to:-

MrPolurajuSir

Submitted by:-

Name :- NITISH SHARMA

Roll No. :- RB5803A18

Trade :- B.tech MBA(CE)

Reg. No. :- 10805210


2/11

ACKNOWLEDGEMEN T

As I began to reflect on magnitude of this project, I was

overwhelmed by guidance and support extended by

Teachers and friends.

I would acknowledge that our H.O.D.

encouragements whose contents made me believe in me.

I would express my sincere gratitude

thanks to ever helping mam. Last but not the least, my heart

goes out to my friend, teacher, Mr.Poluraju sir and my

family whose encouragement, knowledge and supports

makes to do this project presentable.

Thanking you

NITISH SHARMA


3/11

CONTENT:-

1.INTRODUCTION OF PRINCIPLES OF SURVEYING.

2.THE SURVEY PROCEDURE.3.PLANNING.

4.COLLECTING MEASUREMENT.

5.PROCESSING MEASUREMENTS.

6.SURVEY TYPES.

7.TECNIQUES UNDER WATER SURVEYS.

8.MEASUREMENTS.

9.BUILDING SURVEYING.

10.SURVEYING EQUIPMENT.


4/11

Basic Survey Principles:-

Introduction:-

The basic principle of surveying is to be able to work out the position of a point from someother point or points, positioning from the known features to the unknown ones.

To start a survey all you do is to measure the distance between two points on the site thendraw this to scale on a piece of paper, your site plan. By measuring the distance from thesetwo points to other points on the site the other points can be plotted relative to the two initial

points on your plan. You can draw up a network of points joined by distance measurementson your site plan, to scale, as they are on the seabed. Thats it.

Four problems complicate this simple idea:

Sites are three-dimensional so we need to deal with differences in height or depth

Your measurements will have mistakes in them

Your measurements are not perfect

Site plans get complicated when there are lots of points and measurements

The simple survey described above works well enough for sites that are flat, as soon as thereare any significant differences in depth then it stops working. We need to be able to accountfor the differences in depth.

Expect to make mistakes in your measurements. Previous surveys have shown that between5% and 15% of measurements made underwater are wrong so we need to add procedures tofind these measurements.All measurements are not perfectly accurate, they are all plus or minus a bit where only the size of the 'bit' differs. As we will see later, this measurementerror affects the accuracy with which we can position artefacts and ship's structure on our site.


5/11

Where we have lots of points to position on a site the number of points and measurementscan get too large to deal with easily. To get around this problem we set up a network of pointsaround the site from which we position artefacts and structure. The control point network is acornerstone of surveying, it looks like yet more work but in fact makes surveying easier.

The Survey Procedure:-

All survey work follows a simple four-step procedure:

1. Planning2. Collecting Measurements3. Processing Measurements4. Drawing Up

Each step is discussed in detail below:

Planning:-

The actual amount of time the team will spend on site and underwater is usually very short. Itis essential that any work is well planned before it is started so work on site is efficient, safeand problem-free.

The level of detail and accuracy required more or less define the techniques that can be used,these should be specified in the research design. The equipment available and the experienceof the team also limit the techniques that can be used but the overriding factor may be the sitetype.

Collecting Measurements:-

By the time you come to start recording the site the plan should have been explained to allinvolved. This is the point where teamwork and communication become very important. If the team are well briefed before work and de-briefed afterwards then the team leader can dealwith problems as they are found.

Any recording forms that have measurements on them should be well looked after. The formsare the primary record of your work and should be kept even after they have been processed.Keeping a notebook with day to day accounts, speculations and ideas about the site is oftenuseful, the notes can be handy later on when the measurements are being processed.

To be efficient the team needs to be well trained and well practised. If any team member needs a refresher then the survey techniques to be used can be practised on dry land

beforehand.


6/11

Processing Measurements:-

In the processing stage the measurements that have been collected are used to calculate the positions of the points or detail we are trying to record. Often this process is done whiledrawing up the site plan if the points are to be plotted by hand.

For some methods distance measurements are corrected for differences in depth. Depthmeasurements should be corrected for changes in the height of tide during recording. At thisstage any mistakes need to be identified and repeat measurements requested.

Drawing Up

With sketches or measurements collected from your site you can start to create the site plan.The plan may be drawn by hand or drawn on a computer. Computer generated plans are moreuseful as printed copies can easily be made, they can be printed at different scales and thelevel of detail shown can vary as the work progresses.

If the site has not been recorded before then the sketches or assessment survey results can beturned into a site plan. In doing this you are likely to find that something has been missed andadditional work is required.

If a recording survey is being done then the first step is to position the control points aroundthe site on the site plan. Measurements may be needed from the control points to a couple of the main features on the site to align previous site plan with the control points. With thecontrol in place the features can then be added to the plan as they are recorded and processed.

Survey Types

Surveys on archaeological sites can be loosely divided into these types:

y Assessmenty R ecordingy Detail and structurey Monitoringy Topographic

The end product of each of these types of survey is the same, the site is recorded to knownlevel of detail and known precision.

Assessment Surveys

An assessment survey is one that aims to get a rough idea of the extents and layout of a site,it's like a sketch with measurements. These surveys are used to provide information for rapidassessments of sites, by necessity they must be done quickly. The aim is to get enoughinformation about the site as quickly as is possible. These surveys are sometimes done inadvance of a pre-disturbance survey to provide information for planning survey work andcontrol point positions.


7/11

Recording Surveys :-

The most typical type of survey is a recording survey, these include pre-disturbance andexcavation surveys. This type of survey requires careful planning, recording and processingso takes time to do correctly. The first step for a recording survey is to set up a set of control

points around and inside the site, these points are used as the framework for the survey. Oncethe control points are in place they can be used to position artefacts or structure or for helpingto record details of the seabed.

The foundation of a survey is the network of control points installed on the site, this is thefoundation on which the other survey work is built. Permanent, fixed points called control

points or control stations are placed around the outside of the site, if the site is large then points may also be installed through the middle as well. The site should be totally coveredwith simplest possible network of high quality measurements between control points, simplenetworks are easier to install and position. A single point is not enough to set up positioncontrol on a site, a minimum of four points is required. It is essential that the control pointnetwork be surveyed accurately, in most cases the control points should be surveyed to

greater accuracy than the detail.

The positions of larger features can be recorded by measuring their positions relative to anumber of control points. If more than one point on the feature is positioned then theorientation of the feature can also be determined. Over short distances where the highestaccuracy is not required offsets and ties can be used, over longer distances or where the highaccuracy or position quality is important then DSM or acoustic positioning is used.

Recording Detail and Structure :-

Where a feature consists of a number of artefacts in a small area then positioning eachseparately becomes more difficult and can become less accurate. To record a small area to ahigh resolution then drawing frames or photography are used

R ecording the remains of ship's hulls or buildings can be difficult. The remains may be toolarge to record using drawing frames but too detailed to record by positioning only a few

points. Offsets can be useful in recording simple shapes but complex shapes can sometimesonly be captured accurately using close-range photogrammetry. R ecording the remains of harbours and civil engineering works can be difficult because of the size of the task,techniques used for recording topography are sometimes the most useful.

Monitoring Surveys :-

Monitoring surveys are a special kind of recording survey where only selected parts of a siteare recorded, these surveys are done to monitor changes in the site over time. Not all the siteneed be re-surveyed each time, only small parts thought most likely to indicate change. Atypical example would be to monitor the position, attitude and remains of a stern post on anexposed site or the depth of burial of a site under mud.


8/11

Recording Topography :-

A topographic survey aims to record the shape of the seabed and usually involves recordingthe seabed type. The same principles are used for recording topography as for other types of survey, what makes this type different is the need to record over a wide area. R ecording theshape of the seabed usually involves recording the depth or height of the seabed at known

positions. If the measurements are made at regular intervals over the site then a plan can be produced showing the depths as contours.

Techniques : Underwater Survey Techniques:-

There are a number of techniques that can be used underwater for recording sites. Thetechniques vary in accuracy, complexity and cost so not all techniques are applicable for allrecording tasks :

Method Assessment Setting upsurveycontrol

Positioningartefacts

Recordingdetail

Recordingstructure

RecordingTopography

Sketching

Radial

Offsets & ties

3D Trilateration

Drawing frames

Photogrammetry

Photomosaics

Acousticpositioningsystems


9/11

Sketching It is essential to study the site before starting any further survey work and generating a sketch is a good way to do this.

Radial Surveys For a radial survey a diver records the position of features on a site usinga distance and bearing back to a single control point. This technique isvery simple, quick and can be done by a single diver. The technique isnot accurate enough for pre-disturbance or excavation surveys but givesa good enough idea of the site for an assessment.

Offsets and Ties Offsets and ties are used to position features relative to a baselinerunning through the site. An offset measurement positions a featureusing a single measured distance at right angles to the baseline from aknown point, a tie uses two or more measurements from known pointson the baseline to position the feature.

3D Trilateration Three-dimensional trilateration or Direct Survey Method (DSM) usesdistance and depth measurements to position features on a site. Thetechnique is similar to 2D trilateration with the exception that distances

are measured directly to features and the processing deals with anydifference in depth.

Drawing Frames Drawing frames are used to record very small areas of the site in detail.A frame is placed over the area to be recorded and the diver drawsvisible features on a scale drawing or directly on to the drawing frame.

Close-RangePhotogrammetry

Close-range three-dimensional photogrammetry is a very accurate wayof recording complex structures. A number of photographs are taken of the structure from different viewpoints and processed in a computer

program. The program then constructs a three-dimensional model of thestructure to scale.

Photomosaics If a series of overlapping photographs are taken of a site then they can be joined together to form a single large photograph. The photographs can be of the seabed taken vertically downwards or of the side of a structure.Since the tools to do this have become more widely available thistechnique is being used more often. Sufficiently good results can beobtained with a digital camera and the graphics processing softwareavailable found on most computers.

Like close-range photogrammetry and drawing frames, this technique iseffective for small areas but must be used in conjunction with a control

point network.

AcousticPositioningSystems (APS)

Acoustic positioning systems are widely used for survey work in theoffshore industry. These systems effectively replace the tape measuresand dive computers used for DSM with distances measured with sound

pulses. A diver fitted with suitable hardware can be positioned within anarray of acoustic beacons, on the surface the archaeologists can then seewhere the diver is.


10/11

Measurements:-

Distance measurements Distance measurements, tape measures andrecommendations for use

Depth measurements Depth measurements, depth gauges and recommendations

for use

Measurement errors Measurement errors, types of errors, mistakes andadjustments

B uilding surveying:-

B uilding surveying emerged in the 1970s as a profession in the United Kingdom by a groupof technically minded General Practice Surveyors.Building surveying is a recognized

profession in Britain and Australia. In Australia in particular, due to risk mitigation andlimitation factors, the employment of surveyors at all levels of the construction industry iswidespread. There are still many countries where it is not widely recognized as a profession.

Services that building surveyors undertake are broad but can include:

y Construction design and building worksy Project management and monitoringy Property Legislation advicey Insurance assessment and claims assistancey Defect investigation and maintenance advicey Building surveys and measured surveysy H andling planning applicationsy Building inspection to ensure compliance with building regulationsy Pre-acquisition surveysy Negotiating dilapidations claims.

Building surveyors also advise on many aspects of construction including:

y designy maintenancey repair y refurbishmenty restoration

Clients of a building surveyor can be the government agencies, businesses and individuals.

Surveyors work closely with architects, planners, homeowners and tenants groups. Buildingsurveyors may also be called to act as an expert witnesses. It is usual for building surveyorsto earn a college degree before undertaking structured training to become a member of a

professional organisation.

With the enlargement of the European community, the profession of the building surveyor is becoming more widely known in other European states, particularly France, where manyEnglish-speaking people buy second homes.


11/11

Surveying equipment:-

A German engineer surveying during the First World War, 1918

As late as the 1990s, the basic tools used in planar surveying were a tape measure for determining shorter distances, a level to determine height or elevation differences, and atheodolite, set on a tripod, to measure angles (horizontal and vertical), combined with the

process of triangulation. Starting from a position with known location and elevation, thedistance and angles to the unknown point are measured.

A more modern instrument is a total station, which is a theodolite with an electronic distancemeasurement device (EDM). A total station can also be used for leveling when set to thehorizontal plane. Since their introduction, total stations have made the technological shiftfrom being optical-mechanical devices to being fully electronic with an onboard computer and software.

Modern top-of-the-line total stations no longer require a reflector or prism (used to return thelight pulses used for distancing) to return distance measurements, are fully robotic, and caneven e-mail point data to the office computer and connect to satellite positioning systems,

such as a Global Positioning System (GPS). Though real-time kinematic GPS systems haveincreased the speed of surveying, they are still horizontally accurate to only about 20 mm andvertically accurate to about 3040 m.

Total stations are still used widely, along with other types of surveying instruments.H owever, GPS systems do not work well in areas with dense tree cover or constructions.One-person robotic-guided total stations allow surveyors to gather precise measurementswithout extra workers to look through and turn the telescope or record data. A faster butexpensive way to measure large areas (not details, and no obstacles) is with a helicopter,equipped with a laser scanner, combined with a GPS to determine the position and elevationof the helicopter. To increase precision, beacons are placed on the ground (about 20 kmapart). This method reaches precisions between 540 cm (depending on flight height).

basic survey principles

Documents