Surveying

Co tents Introduction Basic principles Plane Table Surveying Chain Surveying levelling Tables

page 1

3 8 11

'9 33

EQUIPMENT

BOAT LEVEL

ALlDADE

o PIN

TRIPOD PLUMB

BOB

Fig 1

PLANE TABLE SURVEY RADIATION METHOD

Factory

------

,,\ MARTINS LANE

A PLAN OF A TYPICAL SITE

Fig 2

ID

CHAIN SURVEYING Chain Surveying has long been established as the easiest an basic form of land mea$urement and is still in common use. 3ased on triangulation and consisting of carrying out the survey in the field and plotting the survey to scale in the drawing office from recorded measurements in the field book. ~t is a job for two people the surveyor and his assistant. There are several possible inaccuracies which may occur '.'hen carrying out a chain survey and great care should be ~aken to avoid the,. The most common being confusing the -~llies, miscounting the links, the chain having knots in ink joints, bent links, the chain not being laid out in a straight line between stations, incorrect bookings, miscalled ·i ensions and booking offsets at wrong points. Practice in ~he field will highlight some of these problems as there is ~o substitute for experience in the use of a chain.

EQUIPMENT The basic equipment for chain surveying is the metric chain 20metres in length with 100 links each .20metres in _e. th. Every tenth link is marked by a brass tag or teller '-i t:-t intermediate tags for every link. The chain is made of E eel wire and great care should be taken when folding so as ~o avoid entanglement and bending the links. When the chain is to be used and laid out it is done by grasping both :a~dles of the chain and throwing it out in one operation and ~ .en straightened out ensuring all links and joints are outst ret ched properly. There are two other chains used these being the Gunter Chain which is 66 feet in total length with 100 links of 7.92 inches, and the Engineers Chain 100 feet in length and :.~E_00 links each a foot long and marked at 10 foot i:r:tervalsv:ith tallies accord.i ng Ly ,

Tapes These are made of steel being the most accurate and being r-e I'e r-r-e d to linen tapes. They are c ornmon.l y in lengths of 10,

20 and 30 metres and are used to measure offsets to the main chci.n line.

11

EQUIPMENT

90 THE METRIC CHAIN

TAPE CHAIN

ARROWS

((

"g 3

RANGING POLES POLE SUPPORT /

.,.

e' 12

ArmlWS .-.•.

0

':c are used to mark the end of each chain line and are

JOOmm to 450rmTl in length and carr-y a red cloth so that they can be easily spotted on the ground.

poles :~ese ere usually 2 metres in length of wood or metal . :n bands alternately in red, white and black.

book _

:::"e_d oak approximately 100mm x 200mm with entries at the back continuing to the front so that the ._:~~c are recorded in the same direction as the Surveyor c.::' -:':::F' along the chain. -C~~~::.~ C.re entered in the book such as hedge"', fence8, ~~~ coundaries, buildings, trees, manholes and poles etc. e afore mentioned are illustrated in Fig.J.

orocedure iE to make a reconnaisance of the site the f,ener~l shape and layout and any other o be surveyed. Then decide on the framework of -.::.----a ion and drive in station pegs A. B. C. as shown in . . :~€ stations to be fixed by taking two tic lines to : ~o that it can be re-located if a return visit is C"~:.~S> If the distance between the stations exceed a ::'e:::-th line in with an intermediate ranging pole as ·f.5. Then by p~oceeding up the chain line from .easure with 90 offsets, features as before u~til you have reached the end of the line A-B, • ::. ";;0" n all the relevant information. This is then 0 -E' ~or B-C and C-A. If the 90 offsets exceed 9 metres -~~.t en an Optical square can be used to give greater r.=-'''''-:'_'''''''~:' or the J:4: 5 Triangle rule employed using a tape. ractical nature of the survey has been carried - ~r_e::ullv checking that all the information required has . ':"noted and loeged the Eurvey can be drawn to scale :!f:..'.'.in[; office.

13

RECONNAISSANCE & SETTING OUT STATIONS

The S· e _.ClllJjAP

,.(~~.

_

Fig 4 14

CHAIN

SURVEYING

intermediate pole

SETTING UP CHAIN LINE

ranging

Fig 5 15

CLINOMETER ~ strument is used for measuring slopes of 3' or is simply illustrated below. By firstly viewing ~nstrument on the horizontal plane the instrument and focussed onto the ranging pole up the ope with the counterweight in the vertical position - ~ ~_evation can be read on the dial, in this case 300• strument is hand held and is most useful for slopes quickly and easily giving instant readings _~s

16

CHAIN

SURVEY

SLOPING SITES To measure "Leg" slopes greater than o 3 , measure convenient horizontal distances, plumb down to ground level to fix point from which to take next measurement.

A

B ~e of slope with CLIlWJ·::ETER ''0(11 Trigonometry AB=AC Cose{.

....---- >--

CLES

--- ---

- -- --- --------- ---

measure slope

c

- - --

---- RANGING ---

OVER HILLS

and B. AssiEtant ~ith pole 2t D lines in surveyor "t C on line AD. Surveyor linef'in pole at D on line sequence ~ith four poles in line.

ft

17

d

b

e

E

B

cain line through A.B.C. set out equal offsets to a.b.c. i~ d.e.Set offsets of length as before to fix D & E. ~~ continuation of main line through F.G. etc.

1Il:dll"\IIWl

G ACROSS A RIVER

'~------~------~------~------~D -----

__

-!:

~_------=rtIVER -

:es at A & B on chain line. AD at Rt. 1s to AB. Pole C na t AC=CD. DE at Rt. 1s to AD, wi t h E.C.B. on straight ::"en AB =DE.

EY OF LAKE OR WOOD - - ~ fraJework of chain lines _= area and triangulate - _ -ies across the corners _:'e'; C:- IN TRAVERSING.

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I TRODUCTION This book has been set out to illustrate the fundamental basis of land measurement and procedures to adopt when surveying areas of land. The actual practice of carrying out surveys has not changed much over the years with only perhaps the refinement and advanced equipment now in use. Wost of the procedures detailed in this publication are in corr~on practice and will give a good grounding to Architectural, Surveying and Building students. It is emphasised t.at only practice in the field will give a good and thorough understandinG of the methods outlined here and the key being accuracy in performance.

1

LEVELLING

___ ~asic instrument for levelling is the surveyors e '!hichis an adaption of Keplers telescope ernp loyang - __ -ex Lenses which produce a real image and line of _ line of collimation (i.e. principal axis) and will -seus sed in more detail later. The other piece of _~-~~- used in conjunction with the level is the _ ~~-_~c _evelling stave in 4 metre and 5 metre heights. -~ :s are taken using the sight line throueh the telescope -_ '= ::"e'.-el onto the staff wlri ch is collimated in metres and Readings of course will be inverted, this will be ater.

.••-:;,_