3 Surveying techniques

Question 1

Definition land surveying

Answer 1

Land surveying is the measuring and recording of the size, shape and contents of any portion of the earth’s surface.

Question 2

What is setting out used for

Answer 2

• A drawing is produced and measurements are translated (from the scale drawing) onto the ground.
• A third element relating to setting out is the calculation of areas and volumes. This is especially relevant where areas of land need to be cut out or filled and the volumes of soil or material need to be known for transportation etc.

Question 3

Definition Setting out

Answer 3

Setting out covers the operations that are necessary to position proposed works on the ground, and to control their dimensions during the construction process.

Basically the opposite of surveying

Question 4

What is land surveying used for?

Answer 4

• to draw up (to a suitable scale) a two dimensional map, plan and /or section.
• As everything is three dimensional, land surveying also includes levelling, which is the determination of the relative heights of different points in the area under survey.
• This information, coupled with the plan, enables a section through the site to be drawn

Question 5

Measuring equipment

Answer 5

• Metric chain
• Measuring tapes
• ranging pole
• arrows
• • Automatic levels – a device mounted on a tripod used to measure levels. Used with a staff.
• Dumpy level – similar to automatic level, slightly different mechanism Wikipedia page.
• Theodolite – a precision instrument for measuring angles in horizontal and vertical planes.
• Electronic distance measurement device (EDM) – a hand tool that accurately measures distance by sending a pulse of light to a surface.

Question 6

Arrows

Answer 6

These are steel pins about 400mm long, used to mark the position of the end of a chain/tape and hold it in position.

Question 7

Tape

Answer 7

Manufactured from steel strands or glassfibre coated
with PVC.
Measurements are more accurate than with a chain 1:2000. However a synthetic tape is not as accurate as a chain, and so should only be used for short measurements.

Question 8

Ranging poles

Answer 8

• These are poles, 2m, 2.5m or 3m long;
• they are painted in bands 200mm or 500mm wide in red and/or black and white, and tipped with a steel point enabling them to be driven into the ground.
• They are used in conjunction with chains or tapes and for marking any points which need to be seen.
• If laid horizontally they are useful for measuring short offsets between chain line and an object.

Question 9

Metric chain

Answer 9

• Available in 20, 25, 30, 50m lengths.
  (20m is the most popular).
• divided into 100 links, and each link is 200mm in length.
• The length of chain is measured from the outside of the handle at one end to the outside of the handle at the other.
• To allow quick observations of fractional parts of the chain, plastic tags (tallies) are attached : either different shapes, or Red at 1m intervals and yellow at 5m intervals.
• Chains are accurate to 1:1000 which is adequate for the majority of chain surveys and setting out.
• Manufactured from steel strands or glassfibre

Question 10

Definition baseline

Answer 10

• A straight line from which I can triangulate or take off sets
• should be easy to refr back to, sometimes a housewall, but not a fence!

Question 11

Running measurements

Answer 11

• recording a series of measurements along a line
• Running measurements are cumulative: if you want to measure 3 points at 500mm intervals you set the tape and measure at 0.5m, 1m, 1.5m; you don’t reset the tape each time for 500mm;
• benefit: reduces accumulated errors

Question 12

Benefits of running measurements

Answer 12

• reduces accumulated errors
• useful along the back of the house. Features such as windows, doors, drains, taps, can be measured directly from this baseline.

Question 13

Offsets

Answer 13

• This is the distance from the chain line/baseline at right angles.
• measurements are taken in a 90 degree angle from baseline to the object, recorde measurement and repeat at regular intervals along the baseline
• • put the zero of the tape at the feature
• Extend the tape across the chain and move it in an arc until the shortest distance is found
• Record the offset length and the distance from the start of the chain line.
• The limit for accuracy is an offset of 8 metres.

Question 14

When is offset needed?

Answer 14

• usefule for measuring curves like windy path, flowerbed, natural pond

Question 15

Triangulation & Trilateration

Answer 15

• triangulation uses angles from fixed points,
• trilateration uses measurements.
• Triangulation involves to keep one line in common between triangles
• • In common practice, the term triangulation is often used for both.
• • The distance from the feature is measured to the chain line in 2 places to create a triangle.
    To ensure accuracy, the sides of the triangle should have approximately equal length sides.

Question 16

When to use Triangulation?

Answer 16

• This is a useful method for plotting boundaries of a site.
• Individual features, such as specimen trees, ramps, steps, gates, archways, water features and statues
• to ‘tie in’ features such as grassed areas, beds, borders, hedges, screens, shrubberies, paths, driveways and rock gardens, by plotting key points, such as corners of the driveway or borders.
• when offset is longer than 8 meters

Question 17

Definition tie line

Answer 17

the survey lines that connect a point to other survey lines - for example when you plot a feature by taking two lines from two fixed points to a feature (i.e. triangulation).

Question 18

Recording a Linear survey

Answer 18

• Identify a baseline - mark a and b point
• make running measurements along the line showing positions of windows, doors if its a house
• Can use offset measurements for any simple 90 degree features closely (up to 8 m)
• use triangulation for many sided or irregular plots

1. make a sketch showing the location of the chosen station and survey lines. Take enough measurements, generally ties from nearby easily recognizable features, and note enough information to enable each station to be relocated if necessary. Pictures will help!
2. Take a bearing of true north from at least one of the lines.

Question 19

Definition Reduced level

Answer 19

Level above or below the datum point.
level on the ground (relative to the datum) at a particular service point

Question 20

Definition levelling

Answer 20

The method of expressing the relative heights of any number of points above or below a plane of reference called the datum.

Question 21

Definition datum

Answer 21

Plane or level surface to which heights are referred

chair example: All measurements are from the floor – this is the level to which all the heights are referred, the datum point

Question 22

Definition official (ordnance) level

Answer 22

Bench mark in ft or m above sea level

Question 23

Definition local datum

Answer 23

Where no Ordnance bench mark is obtainable, a local datum point like a step or wall is given an assumed value, e.g. 50 metres.

Question 24

Definition backsight

Answer 24

First reading taken after the level has been set up; usually taken on a bench mark or local datum point.

In surveying the first reading is always taken onto the Bench Mark and it is called a Back Sight (BS).

Question 25

Definition Foresight

Answer 25

Last reading taken before the level is moved.

The last reading taken before moving the level is called a Foresight (FS)

Question 26

Definition intermediate sight

Answer 26

A reading taken between backsight andforesight.

All readings taken in between are called Intermediate Sights (IS).

Question 27

Definition station

Answer 27

position where readings are taken.

Question 28

Definition change point

Answer 28

a station where two readings are taken during the re-siting of the level. The measuring staff remains in place, and the first reading to it is the foresight. The second reading after the level is moved is to the staff as the backsight.

The staff position whee the levelling instrument is moved

Question 29

Definition line od collimation

Answer 29

The height of the levelling instrument or the line of sight parallel to the horizon, an ‘artificial horizon’.

Question 30

How do you do surveying leveling

Answer 30

done wirh an instrument and a levelling staff

Levelling involves taking pairs of spot heights in order to determine differences in elevation so that profiles can be drawn.
The key point about levelling is that:
• An artificial horizon is set up from which downward measurements are taken.
• The artificial horizon is called the line of collimation.
• Since the readings are taken downwards, higher readings will indicate the ground is lower.

Question 31

Levelling staff

Answer 31

The staff is 3, 4 or 5 m long; metal staffs are usually telescopic and wooden ones folding.
The staff is painted in red and white or red, black and white to make it easier to read.
Readings through the various levels will be upside down, so the calibration of the staff is designed to be read that way – it is inverted.

Question 32

Scale rulers

Answer 32

Scale rulers are used to simplify drawing to scale, although it is equally possible to draw to scale using ordinary rulers and calculating the scale.

scale Measurement drawing
on ground measurement

1: 1 1 meter 1 m
1: 20 5cm
1: 50 2 cm
1: 100 1 cm
1: 500 2 mm

Question 33

Choice of scale

Answer 33

• 1:100 is a useful scale for medium to large gardens. It is also suitable for showing trees in planting plans, or larger specimen shrubs.
• 1:50 is a useful scale for a small garden or for planting plans
• 1:20 would be useful for more detailed drawings, such as hard landscape features and construction details
• Scales such as 1:200 or 1:500 are used for larger landscape sites

Question 34

What does a site plan need to include To enable interpretation

Answer 34

The site plan should include:
• The scale used
• an arrow with the direction of north
• a title block giving details of site and date
• a key or labels to identify features recorded.
* symbols to make sure one knows what is what

Question 35

How is a plan laid out on paper?

Question 36

How can levels be represented on a site plan.

Answer 36

• Contour lines
• xxxxxxxxx fill,in

Question 37

What are sections and elevations used for in a site plan?

Question 38

Designer plan

Answer 38

Designer’s Plans

• Location plan (marking where site is on a map)
• Zone map (shows soil type, microclimate etc)
• Site survey
• Concept plan (shows problems and solutions)

Question 39

Benefits of garden planning

Answer 39

• knowing the space much better and its details (gardens are hardly never straight….j
• Drawing a scale plan helps to create a design that works
• makes it possible to order the correct quantities of materials,
• saving money, time, and inconvenience.
• a lot easier (and cheaper) to change your plans on paper than it is to change a terrace or pathway once it’s built.

Question 40

Client plan

Answer 40

Plans for Client

• Sketch design
• Final design
• Sketches, elevations and perspective drawings

Question 41

Construction plan

Answer 41

Plans for Construction

• Construction details
• Hard works layout plan (BSI graphics, structures and levels)
• Services
• Planting plan
• Setting out plan (dimensions, measurements and offsets)

Question 42

Solutions for measuring an established / overgrown garden

Answer 42

• lot of established plants that make access impossible to measure the boundary, then you will need to improvise.
• There are several things you can do:
  1If the boundary outside the garden is more accessible, e.g. next to a road, it’s much easier to measure the length of the fence from outside your property rather than crawling through bushes inside it.
• 2If there is a plant preventing you measuring to the end of the garden take a long cane or broom handle, push it underneath the plant until it hits the boundary. Then measure how far under it went and add that onto the tape measurement you have so far.
• If you can’t measure the length or width at the boundary because there are plants in the way, take your measurements just in front of the plants. Make note of how far up the garden you are for this measurement
• if only one corner is accessible to take cross measurements from because of shrubs on the one side, then This is OK because if one corner is correctly positioned, it’s often enough to get the rest of the measurements to plot correctly.
• To plot trees and other features onto your plan, Measure the tree or feature from two different locations so that you will be able pinpoint it precisely on the plan. Whenever possible take these two cross-checking measurements from the house because that will be your fixed starting point on the plan.

Question 43

Solutions to measure a complex garden

Answer 43

Do lots of of sets along a baseline

Sometimes it is just not possible to get close enough to the boundaries on each side of the garden to measure accurately. On those occasions you’ll need a different survey method.
Run a tape measure down the length of the garden from the house to the end. Make sure the tape is a 90 degree angle to the house. Over long distances, it will be difficult to do it perfectly at 90 degrees, just do the best you can.

Then with a second tape measure held at 90 degrees (right angle) to the first tape, measure across the garden wherever there are gaps in the plants that allow

Question 44

How to identify north

Answer 44

• with a compass, many phones have an app for this
• can look at the deeds of a ur property. There should be a tiny Ordnance survey plan; this will show you the location of North.
• go online and put your postcode into Google Maps, or Bing, or any other mapping service. Go to the ‘Satellite’ setting so you can identify your property and see where the North arrow is in relation to your house.
• at midday when it’s sunny, see which direction shadows fall – this will be North
• Whist you are gathering this information about your garden, it’s also a good idea to view the garden at different times of the day. Pay particular attention to the times you are most likely to use it. Is the main patio area likely to be in sun or shade when you’ve finished for the day? Perhaps a second seating area may be needed?