guide to basic surveying

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Guide to Basic Surveying


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Contents

2. Introduction, Graphic recording

3. Drawing scales, Publication issues, Drawing materials, Drawing symbols

4. Field survey symbol sheet. Fig. 1

5. Building plan with explanatory captions scale1:100 . Figure 2

6. Methods of survey: Field sketch. Fig. 3.

7. Annotated Field sketch. Fig. 4

8. Methods of survey: Dimensioned sketch

9. A dimensioned sketch. Fig. 5

10. Methods of survey: Tape and offset survey (extended baseline survey) Fig. 6

11. Tape and offset survey in a single building. Fig. 7

12. Methods of survey: Plane table and alidade survey. Fig. 8

13. Plane table and alidade survey carried out to record detail. Fig. 9

14. Methods of survey: Elevations and Sections. Fig. 10

15. Plan and elevation Fig. 11, and section Fig. 12 through a black house

16. Plan of a Perthshire township, drawn with plane tables scale 1:250

17. Plan of a Benbecula farmstead, drawn with plane table and offset scale 1:200

18. An Aberdeenshire farmstead, drawn with plane table scale 1:500

19. A Dumfriesshire settlement, survey and AP transcription scale 1:2500

20. Examples of location maps scales 1:1000 and 1:2500


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2

Introduction

There is a growing interest in our built heritage, the

subject matter ranging rom prehistoric monuments and

historic townships to more modern military or industrial

sites.

Studying a subject can include carrying out

documentary research and looking at extant remains.

The record can include old documentation and maps,a written description, photography and sketches or

measured survey drawings.

This guide is intended to assist in the process o

graphically recording extant remains. It has been

created in the context o the Scotlands Rural Past

project where the range o survey equipment available

to the participants will be limited and describes

traditional survey methods using plane table, alidade

and tape measures. Most o the examples used in

this guide are o post-medieval remains but the same

survey techniques can be used to record all types o

buildings and sites.

Graphic recording

The purpose o graphic recording is to provide a set o

drawn illustrations (e.g Figures 13 -17) to provide a record

a site at a point in time that can be viewed and used or

research by other interested parties.

A graphic record o a building or structure normally

takes the orm o a combination o plan, elevation andsection drawings. Perspective or 3D orthographic

views can also be created as required.

t o graphic recording, oten undervalued,

is the process o surveying itsel.The surveyor is

required to spend time looking at and understanding

the site or building. Drawing, in either sketch or

accurate scale orm, is a subjective process requiring a

clear understanding o what is to be drawn. I a complex

eature is not understood on the ground it is unlikely

that the survey drawing will produce a clear depiction.

It is necessary to make inormed decisions on what thekey elements o a structure are and how to depict them

using lines or symbols. The amount o detail will vary

according to scale.

Understanding the process o generalisation, i.e. using

ewer lines to represent a structure at smaller scales, is

also crucial to the success o the depiction. The smaller

the scale, the more generalisation takes place but

overall shape and orm must not be lost.

A plan, (Figure 11a) in the case o a building, is a horizontal

slice, usuallly above window sill level,to show foor

layout, posi tion o doors, windows, replaces etc.

For an earthwork a plan is a view looking down on to the

eatures rom above.

An elevation, (Figure 11b) is a view looking on to an

upstanding structure or wall to show position and height

o eatures.

A section, (Figure 12) is a vertical slice through a building

or stru cture to show foor levels, ceiling heights andwall thicknesses. For an earthwork a section would show

a ground pro le and the height o banks, etc.

.

.

.


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Drawing scale

A clear understanding o what a survey is trying to

convey is essential in the selection o an appropriate

survey scale. Beore starting the survey time should be

spent walking over the site to determine its extents and

boundaries.

What are you trying to illustrate: the site location,position in the landscape, position relative to other

buildings, size and orm o the structure itsel or a

detailed part o a building?

Too small a scale can make it impossible to depict

important archaeological detail, too large a scale

ort, oten without any

useul gain in inormation. It is better to show the whole

c areas as

required to show more complex detail.

tting the drawing

onto the drawing board. I too large a scale is used,the resulting survey may need to be spread over more

than one sheet. This becomes unwieldy and may cause

problems i the drawings need to be re-sized or use in

a report.

The logical approach is to create a suite o illustrations

that may include:

Individual building or structure

1:50 - 1:100 is used to show the detailed character o

a single building or monument, e.g. a hut-circle, cairn,

replaces, drains,

agstones and stairs can be depicted accurately

without recourse to symbols.

Details or eatures

1:20, 1:10, 1:5 up to 1:1 or enlargements can be usedto illustrate particular eatures, such as carved stones,

les and excavation details, as required.

Publication

Survey drawings or derivatives are oten incorporated

into a publication or report. These reports are normally

A4 or smaller in size, so consideration has to be given

to the size o the original drawings otherwise over

ect the printed quality.

RCAHMS generally works to 50% reduction as astandard.

Drawing materials

RCAHMS survey drawings are intended to provide a

permanent record. To achieve this, Hi-Polymer (eg 6H)

lead penc ils are us ed on a p olyester lm, giving a

waterproo, dimensionally stable archive medium.

Drawing symbols Figure 1

A specic set o conventions and symbols is used to

depict eatures at various scales. A sheet showing the

symbols used by the RCAHMS at various scales is

included on the ollowing page.

The ollowing range o survey scales is used by

RCAHMS:

Location map Figure 17

Should be at an appropriate scale to show the

geographical location o the site.

Topographic or landscape map Figure 16

1:1250 - 1:2500 is used to show eatures within their

topographic setting. The level o detail o man-made

eatures at this scale is limited to outline shapes and

eld

banks, etc. Natural eatures can be illustrated using

hachures or contours.

Site plan Figures 13 -15

1:200 - 1:1000 is used or a site plan to show the

relationship o a group o man-made eatures, such

as a armstead or prehistoric settlement, with related

buildings. This scale allows the illustrator to representsome o the character o the structures, together with

their relative positions also structural elements such as

blockings and straight joints.

A small-scale map to show geographical location.

A larger scale map to show topographic setting o

a building or group e.g. a mill with the mill lade and

river.

A site plan to show the relative positions o a groupo buildings.

A plan and elevation to show the character o an

individual building.

replace.

.

.

.

.

.

Figures 2 & 11


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Figure 1 - RCAHMS Field Survey Drawing Conventions


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Hatching indicates ablocked window

Hatching in thestonework indicates that

replace has beeninserted later

Large ooting stones at the base o the

building have been drawn individually

Wall above sill level

Wall below sill level

Dashed lines indicate that theacing stones o the wall haveallen out and that only wall

core remains

Short triangular hachuresindicate a man-made slope

whichhasbeencuttocreateadrain behind the building

A straight joint indicates that thebuilding has been built in two

phases,thelowercompartmenthaving been added on to the

original building.

Dashed line indicates original lineo wall beore collapse

Cruck slots in wallor roo supporting

timbers

Window opening

Hatching indicateslater addition

Byre drain visibleoor

Door opening

Dashed lines show theposition o the cruck

timber (no longerpresent)

Upstanding walls may be letunshaded at a scale o 1:100

Drain

Figure 2 - 1:100 scale building plan with explanatory captions

Grounded boulders


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Methods of survey

The following pages provide an outline of several survey

methods that can be carried out with simple surveying

equipment:

Field sketch

Dimensioned sketch

Tape and offset survey (extended baseline survey)

Plane table and alidade survey

Each of these methods can provide a very useful record in

its own right. However, often the most effective way to

survey a site is to use a combination of the different

methods.

Field sketch Figure 3 (below)

Undertaking a field sketch provides and extremely

useful way to gain an overview of your site and is an

ideal way to assess the number of buildings and other

structures present, as well as aspects of their construc-

tion, phasing and spatial relationship. A well-drawn field

sketch can provide a very useful record of a site or

building in its own right, or may become the first stage

in the process of producing an accurate scale drawing.

At its simplest, a field sketch need only show building

outlines and orientations (see below). In this example,

building walls standing above sill height are shaded

dark; walls below sill level are stippled; enclosure walls

are shown in outline only. Cruck slots, doorways,

window openings and fireplaces are all shown

and highlighted below.

Always remember to include a north point.

Window

Fireplace

Doorway

Cruck slot

Sub division

Doorway

Figure 3 - Field sketch


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Field sketch. . . . . . annotated Figure 4 (below)

You can increase the value of your sketch by adding notes

and measurements.This will assist your interpretation of

the site when it comes to writing a site description. In this

example, the distance between cruck slots has been

recorded, and the locations of a blocked doorway, window

lintels and a byre drain are all marked.

Equipment required for field sketch:

Paper and pencil

Figure 4


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Dimensioned sketch Figure 5

A dimensioned sketch takes the field sketch one step

further. The aim is to annotate your sketch plan with

accurate measurements to show wall lengths and

thickness. It should include all the necessary dimensions

for someone who has not seen the building to under-

stand it and, if required, construct a scale drawing.

Sketches should be neat, in proportion and large enough

to allow the required dimensions to be clear and legible.

Cumulative measurements, known as running sizes

taken from a single point of origin are preferable to a

series of separate measurements and usually run in a

clockwise direction round a room, or building (see figure

5 opposite for clarification). The origin point for running

sizes should be clearly marked.

Room diagonals and wall thickness measurements should

be included. This method is appropriate for plans, eleva-

tions or details of relatively simple buildings or structures.

Equipment required for sketch survey:

Drawing board, paper and pencil, 30m tape, 5m metal

tape, survey pin, bulldog clips.


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Figure 5 - Example of a dimensioned sketch

Point of origin

Direction of progress


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Tape and offset survey (extended baseline survey)

Tape and offset survey can be used to create accurate,

scaled plans of both small (e.g. a single feature) and larger

areas (e.g. an entire township).

This survey involves establishing a baseline, through, or

parallel to, the features you want to map, and measuring

the distance of the features from this known line (see

figure 6).

To create a baseline, stretch a measuring tape taught

along the ground and hold it in place with pegs.To help

you get a straight line, place survey poles in the ground at

regular intervals so that you can check your line of sight.

The length of your baseline is determined by the size of

the area you want to survey. Once set up on the ground,

plot your baseline though the centre of a sheet of A2

graph paper.

To record points of interest, measure along the tape (or,

baseline), then take a measurement at right angles fromthe tape to the point you wish to record (see figure 5). Plot

these measurements on to your graph paper.The

accuracy of a right angle can easily be checked by basic

triangulation (3-4-5 triangle), or by using a cross-head

ranging pole which allows you to sight a right angle off

your baseline.

Figure 6

Single measurement along an offset is the most

convenient way to plot a point. However, where

the offset is more than 1m, it is more accurate to

use triangulation: measure the distance to the

feature from two separate points on the baseline

and plot where they cross with a compass, or, a

set of dividers (see figure 6 for clarification).

If you are recording large areas, such as a whole

settlement, it is best to set up a series of

baselines across the site.If you are working in a

group,you can rapidly complete a survey in this

way, by dividing the site amongst different

people.

Equipment required for tape-and-offset survey:

Drawing board, graph papers, pencil,compass,

ranging rods (including cross-head), 30m and/or

50m tapes, steel hand tape, land arrows or pegs.

Gridded paper or lm

Primary baseline

Subsidiary baseline

Right angle oset -

subsidiary baseline

3-4-5

Ranging pole

Ranging pole

Cross-site ranging pole

Creating a right angle


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Figure 7 - Example of a tape and offset survey used to capture detail in a single building

Trianglated measurements from

two known points can be plotted

with compass or dividers

baseline

offset

offset


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Methods o survey: plane table and alidade survey Figures 9, 13 -16

This is a method o survey that allows a surveyor to

plot and create an accurate scale drawing on site. The

ts onto the

drawing board.

xed to a

tripod, levelled, and orientated.

An alidade is a sighting device used to observe the

salient points o the site.

Have a good look at the site

Beore you start the survey, time should be taken to

walk round and have a good look at the site or building

that you are going to record. On a building, the obvious

eatures that you would want to record are the corners,

replaces. More subtle

eatures that you would look out or are changes in wall

direction, straight joints, blocked doors or windows,

oorcovering, byre drains.

Select a survey station

Once you have had a good look at the site, you will

select a position or your survey station rom which

you have a line o site to as many o the main points

as possible. It is particularly important to be able to

see corners and places where a eature has a change

in direction. Set up the tripod legs over your selected

survey station.

Prepare the drawing boardlm is taped onto the

drawing board with masking tape.The corners are

lm pulled tight, and then the edges

xed onto the tripod.

Orient the drawing board

When drawing a building you would orientate the long

side o the board so that it is parallel to the long axis

o the building. I possible, or a site plan, you would

oriented the board so that north is up the page. For

all plans it is important to check that the whole site is

t on the board at your chosen scale. A pin

xed point rom

which observations and measurements can be taken.

The pin marks the position o your survey station on

the board. Once the survey has commenced the plane

table should not be moved.

Carry out the survey

The alidade is placed against the pin and used to

observe in turn, selected points. Rays are drawn on

lm and measurements between the pin and the

points taken with the 30m tape. The measurement is

written onto the drawn ray as a record. Subsequently,

each point is plotted along the ray at the selected scale,with a scale rule. Observations and measurements are

taken to as many points as required to allow the shape

to be recorded. These plotted points create an accurate

ramework around which the rest o the plan can be

constructed. This method is most useul or plans o

single buildings or small sites within a radius o 30m

rom the plane table.

Larger sites

For larger sites multiple stations will be required. Thesecond station must be plotted accurately onto the plan

rst station and marked on the ground. It must

rst station (see Figure 13).

Equipment required or a plane table and alidade survey:

Plane table, tripod legs, alidade, spirit level,

30m tape, polyester drating lm, hi-polymer 6H

pencil, masking tape, pin, scale ruler, compass, ranging

rod or sighting, plumb bob.

Figure 8 - A plane table and alidade as supplied by SRP


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Figure 9 - Example o a plane table and alidade survey carried out to record a single building


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Methods o survey: creating an elevation Figure 10 (below) 11 & 12 (opposite)

An elevation is normally created ater a plan o a

building has been completed. An elevation drawn

lm gives a good,

clear representation o a building. In a similar way to a

plan, i the building is not going to be drawn on site, all

measurements can be recorded onto a sketch.

In order to measure elevation heights to add to the

drawing, a datum line must be established across the

ace o the building. The datum is created using a string

xed into position and levelled, using a hanging

string level. This datum line would normally be set at

a height that runs through the middle o the windows

and doors so that tops and bottoms o the eatures can

be measured easily and noted in a clear way. Where

the datum string does not touch the building or it is

cult to take a measurement, a builders spirit level

can be used to transer the datum onto the structure.

A simple chalk line is marked to indicate the datum.

Measuring an elevation is similar to carrying out ax

requires one measurement along the datum line and

one measurement up or down rom the datum line.

I a drawn plan exists, the elevation drawing would be

lm over the plan

the positions o the building corners,

door and window openings or blockings that will be

visible on your elevation. These positions are then

lm on which you are going to draw

your elevation. At these points, where the distance

along the building is known, a 5m steel tape can beused to measure up or down rom the datum line to

obtain the height. The position o the datum line and

o the points are drawn onto your elevation. Once the

detail that has a known plan position has been plotted

onto your drawing, you will have the bare bones o an

elevation.

distance along the datum as well as a height. These

distances and heights can be recorded onto a sketch

survey or a second person can take measurements and

call them out as you draw. Establish a horizontal zero

point on the datum line. In the case o a straight sided

building you might choose the let edge o the building.

I surveying an irregularly shaped building you may

chose a point to the let o any detail that you wish tomeasure in. (A scale rule is marked rom the let so it

is always easier to measure and plot the distances in

the same direction.) A series o points are measured

ne the shape o the building, ground

level, openings, sills, lintels, string courses, chimneys,

roo angles and heights. It is oten easier to get a

measurement or the height o the roo inside the

building.

Once the outlines have been plotted onto the elevation,

it is easier to plot minor detail by measuring rom the

nearest building eature, or example a set o running

sizes can be taken rom the top to the bottom o thewindow to position the joints between the stonework. In

this way all the minor detail that you wish to depict can

be added bit by bit until the elevation is complete.

The section drawing o the Benbecula black house

which was created at the same time as the plan

and elevation has been included to show the kind o

detail that would be recorded on such a drawing. The

methodology or creating a section drawing is not being

dealt with in this guide.

Equipment required or an elevation:

ranging rod, (data board, paper and pencil i doing

a sketch survey),

(plane table, tripod legs, polyester drating lm, hi-

polymer 6H lead pencil, set squares, T square, masking

tape, scale rule, paper and pencil i drawing elevation

on site).

Figure 10 - Example o a sketch survey or an elevation showing some o the sizes which need to measured.

String, line level, chalk, 30m tape, 5m steel tape,

You can now start adding detail or which you need a


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Figure11a Plan and elevation Figure 11b o a Benbecula black house which has been converted to a byre, originally drawnat 1:50 but reproduced here at 1:100

Figure 12 - Section o a Benbecula black house, drawn and reproduced at 1:50

Stone detail may

be completed rom

photography

Thatch

Tur

Rater

Collar

Draininsertedlater

Window converted to a door


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30m

rang

efro

mStatio

n2

30mrange

fromStation1

level

Survey points should be taken on the same side of a feature to avoid confusion.In this case points have been taken on the outside edge of the wall.

,

Cobbling with well defined edge

drawn in on revetted terrace


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Figure 14 - 1:200 scale site plan o a Benbecula armstead drawn with a plane table supplemented with oset measurements.

(The building on the right hand side is also shown in detail at scale 1:100 in Figure 11b on page 15.)


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Figure 15 - 1:500 scale site plan o an Aberdeenshire armstead created using a plane table

Stackstands

Horse-gangplatorm

Upstanding

buildings

Footings o stonebuildings and walls

Buildingvisibleonlyas a slightly raisedbanks o tur

Long dashed hachures areusedtodepictanaturalslope

Quarry

Footings o buildingwith some visibleacing stones

Outcrop

Marsh symbols areused to indicateboggy ground


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Figure 16 - 1:1250 scale landscape map o an 18th century Dumrieshire settlement and eld-system

derived partly rom an Ordnance Survey base plan and rig and urrow added rom vertical aerial photographs.

Stone dyke

Stone walled

buildings

Lines o broad rig & urrows -

added rom aerial photographs

Tur eld banks

Short hachures are used to dep ict

the hollow that denes the trackA series o tur banks anddepressions show an UnenclosedPlatorm Settlement


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guide to basic surveying

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