Specification
Land and Trackwork Surveys
SECTION 22
Survey control
generally
LAND AND TRACKWORK SURVEYS
1
Survey control shall be established by the Contractor at a density
sufficient to achieve the specified accuracy.
All surveys shall be in SI metric units, and shall be co-ordinated by
northings and eastings referenced to Ordnance Survey National
Grid.
(22.001)
Permanent ground
markers
2
Permanent ground markers (P.G.M.) intended for survey control
shall be constructed at all control stations and primary and
subsidiary traverse stations and shall be placed in stable and
protected locations out of trafficked areas and suitable for frequent
access and possible use for future setting out. Where practicable,
P.G.M.s shall not be located within 3.0 metres of any rail. P.G.M.s
may also be used as bench marks.
Where a preferred marker location is away from the main survey
area, or outside the Railtrack boundary in private lands, the
Contractor shall agree the marker location with the land owner
before such markers are installed.
For string line survey pegs, the taping offset dimension shall not
exceed 5.0 metres without triangulation to the pegs, and string line
pegs shall be placed not more than 2.0 metres from the nearest rail.
Unmarked pegs shall not be left so as to constitute a tripping
hazard.
Where possible ground markers shall be positioned at a density of
at least two stations per hectare in open ground, and at
approximately 100 metres intervals for longitudinal trackwork
surveys. The distance between permanent ground markers may be
increased in open locations, but the interval used shall allow for
survey closure to the specified accuracy utilising the survey
equipment proposed by the Contractor.
New instrument stations shall be established either by conventional
traversing or by GPS baselines between adjacent stations. Each
instrument station shall be visible from and connected to at least
two other survey stations.
New instrument stations shall be established to better than ± (3
mm + one part in 30,000) horizontally and ± (3 mm + 3 mm /km)
vertically relative to the nearest P.G.M.
Domed brass rivets of suitable design shall be placed in permanent
structures by drilling and fixing with an epoxy resin compound or
internal clamping device. Earth anchors and ground markers shall be
used in open ground. Other designs for survey stations may be
used subject to prior agreement by the Employer’s Representative.
Specification
Land and Trackwork Surveys
The grid to which the site survey shall be related shall be
(INSERT).
The accuracy to which the survey grid shall be fixed to the
Ordnance Survey National Grid shall be /±20 mm. /±150 mm. /
(22.002)
Accuracy
3
A closed ground control network shall be established prior to
linking individual survey detail elements.
The survey method shall be appropriate to the required accuracy.
Adequate checks such as equipment calibration, survey closure
methods and calculations shall be carried out for all survey
techniques used to maintain the specified accuracy.
Unless specified otherwise in the relevant Clause, the maximum
error between permanent survey control stations shall not exceed
1 in 20,000. For distances between adjacent survey control stations
of less than 200 metres, the maximum error shall not be greater
than ± 10 mm.
Unless specified otherwise in the relevant Clause, the height
difference between any two points used as permanent bench marks
½
shall not be in error by more than ± (12k ) mm, where k is the
distance in kilometres between the two points being considered, or
± 5 mm, whichever is the greater, except for river to lake bed levels
which shall be measured to ± 50 mm.
The accuracy achieved in longitudinal distance, and height shall be
quoted on all survey plans.
(22.003)
Schedule of survey
control stations
4
A series of individual indexed diagrams shall be prepared by the
Contractor detailing for each permanent survey control station:
(i)
general location,
(ii)
description of marker type,
(iii)
control station designations,
(iv)
survey grid co-ordinates,
(v)
reduced level to scheme datum,
(vi)
tie dimensions to at least three easily recognisable and
durable features located within, if possible, 50 metres of
the control station.
A copy of the schedule of permanent ground markers shall be
provided to the Employer's Representative.
(22.004)
Control diagrams
for survey markers
5
A control network diagram defining the horizontal and vertical
interrelationship between permanent survey control stations,
including designation, distance, angles, reduced level, type etc shall
be prepared by the Contractor.
(22.005)
Specification
Land and Trackwork Surveys
Level datum
6
All levels shall be related to Ordnance Datum Newlyn height datum
except for isolated surveys where a level datum proposed by the
Contractor may be used with the agreement of the Employer’s
Representative.
The value of the datum bench mark to which the survey is related
shall be confirmed by check levelling out and back to at least one
other existing permanent bench mark.
The location, designation and value of the datum bench marks used
shall be quoted on each survey plan.
(22.006)
Site bench marks
7
A minimum of three site bench marks shall be established on
existing stable features at, where possible a minimum density of one
per map sheet.
A diagram shall be prepared for each site bench mark showing its
location dimensioned to at least three easily recognisable and
durable points located, if possible within 5.0 metres of the site
bench mark.
A simple plan shall be provided to the Employer’s Representative
showing the vertical control network and the inter-relationships
between bench marks.
(22.007)
Site details to be
surveyed generally
8
The planimetric features to be surveyed shall be:
(i)
control points,
(ii)
buildings and structures,
(iii)
boundary features,
(iv)
roads, tracks and footpaths,
(v)
street furniture and visible service features,
(vi)
water, drainage and coastal features,
(vii)
slopes and earthworks,
(viii)
woods, trees and recreational areas,
(ix)
industrial features,
(x)
trackwork, bridges, structures, train operating equipment.
The absolute plan position of any well defined point of detail shall be
correct to within ± 0.3 mm root mean squared equivalent at the
plan scale checked from the nearest survey control station.
Co-ordinates and levels shall be obtained by direct measurement of
each point except as follows:
(i)
where the ground surface is obscured by thick vegetation,
Specification
Land and Trackwork Surveys
(ii)
where there are expanses of water, the water level at the
time of the survey shall be used, unless soundings have
been specified,
When height points are to be interpolated from a surveyed
framework of levels, details of the Contractor's proposed
method shall be submitted with the Tender. The method
used shall define the ground surface to the same accuracy
as direct measurement.
Mature trees shall be identified by species and girths and spreads
plotted. Overall extent of the canopy shall be shown where it is not
possible to identify individual trees.
Features which cannot be surveyed to the specified accuracy
without extensive site clearance shall either be surveyed
approximately and annotated accordingly or where specified in the
Contract, arrangements shall be made to clear the Site to enable the
survey to the specified accuracy to be undertaken.
(22.008)
Height
information
9
Sufficient spot levels shall be surveyed such that true ground
configuration is accurately represented on the plans.
The maximum distance between adjacent spot levels shall be
(INSERT).
Ground survey spot levels on hard surfaces shall be correct to
± 10 mm r.m.s.e. except on ploughed or otherwise broken surfaces.
Where specified, contours shall be shown at vertical intervals of
1.0 metre.
At least 90% of all contours shall be correct to within one half of
the specified contour interval. Any contour which can be brought
within this vertical tolerance by moving its plotted position in any
direction by an amount equal to 0.1 of the horizontal distance
between contours, or 0.5 mm at plan scale, whichever is the
greater, shall be considered as correct.
Contours which cannot be surveyed to the specified accuracy
without extensive site clearance shall be surveyed approximately
and annotated accordingly on the plan.
In flat areas where the horizontal distance between contours
exceeds 50 mm at plan scale, supplementary spot levels shall be
surveyed at intervals not exceeding 50 mm at plan scale, parallel to
the contours.
(22.009)
Specification
Land and Trackwork Surveys
Underground
services generally
10
For the services specified in Clause 22.011, underground service
information may be taken from statutory authorities' or other
service owners' record drawings and plotted to agree as closely as
possible with surveyed surface features.
For the services specified in Clause 22.011, accessible manhole
covers and inspection chambers shall be lifted where permissible
and a direct visual survey carried out. The number of underground
access points and where possible the type of services, with numbers
of cables or drains shall be identified.
Routes of buried services between access points may be taken from
record drawings and plotted to agree as close as practical with
surveyed surface features. Railtrack personnel and other on site
personnel with local knowledge shall be consulted, where available,
to assist in identifying routes of buried services and utilities.
The ends of inaccessible service routes shall be investigated initially
by visual survey and for the services specified in Clause 22.011,
supplementary surveyed by electronic or other tracing methods.
For the services specified in Clause 22.011, verification by
excavation shall be carried out. Excavation and backfilling shall be in
accordance with Sections 50 and 51: Excavations.
(22.010)
Services to be
surveyed
11
The schedule of services in the form of a tick list to be surveyed are
listed in Table 22/1.
Table 22/1
Service
Specify service if
applicable and insert
where applicable
!C!
Records
Direct
Visual
Electronic
Excavation
tracing
Surface water drainage
Foul drainage
Water
Gas
Electricity
Telecommunication
Other services
Other underground
utility features
RT signalling cables
RT power cables
The following data shall be recorded for each underground
chamber, catchpit, manhole and the like:
(i)
shape of unit with principal plan dimensions together with
sidewall and centre depths,
Specification
Land and Trackwork Surveys
(ii)
width and levels of all channels and pipes. Levels shall be
taken at regular intervals and in any event at not more than
5.0 metres centres,
(iii)
invert level, material, location and diameter of all pipes,
bellmouths and valves together with direction of flow,
(iv)
top and bottom water levels of all underground structures.
Where information is derived from statutory authorities' or other
Service owners' record drawings, a schedule shall be provided giving
full details such as record office location, drawing number, scale etc.
(22.011)
Measured
structure and
building survey
12
The absolute plan position of any well defined detail shall be
accurate to ± 0.3 mm r.m.s.e. at the specified plan scale, when
checked from the nearest survey control station.
Directly measured dimensions within building surveys shall be
quoted to the nearest 10 mm.
The following data shall be recorded for each bridge, retaining wall
and the like:
(i)
vertical and horizontal clearances from rails,
(ii)
heights of parapets, soffit levels etc,
(iii)
alignment of track,
(iv)
dimensions of main structural members,
(v)
materials of construction,
(vi)
elevations.
The following information shall be recorded for each building.
(i)
building outline,
(ii)
floor plans,
(iii)
roof plans,
(iv)
sections,
(v)
elevations.
Further to Clause 22.003, the level of accuracy required is
(INSERT).
(22.012)
Specification
Land and Trackwork Surveys
Accuracy for
trackwork survey
13
All points shall be recorded to an accuracy of ± (5 mm + one part
in 30,000) horizontally and ± (5 mm + 3 mm /km) vertically relative
to the nearest P.G.M. Adjacent features within 10 metres shall be
recorded to a tolerance not more than 5 mm.
Lateral and vertical clearances to the track or road at bridges,
tunnels, canopies or platform faces etc, shall be recorded to an
accuracy of ± 3 mm. Directly measured fixed infrastructure
dimensions more than 10 metres from the track may be quoted to
the nearest 100 mm.
(22.013)
Survey interval for
trackwork
14
The survey interval for trackwork shall be as follows:
(i)
On straight track, the running edge of the rails shall be
surveyed at 10 metres intervals,
(ii)
On curved track, both rails shall be surveyed at 10 metre
intervals for a radius greater than 500 metres, and at
5 metre intervals for a radius less than 500 metres.
Where a Hallade type curve survey is specified, the curve survey
half chords shall be marked out and used as the survey reference
points on the curve.
Chord points shall be related to mile posts or chainage mark, with
chord point numbering starting at the top of the ramp London end
of any station, with decreasing numbers towards London.
(22.014)
Information to be
shown on drawings
of trackwork
survey
15
The following information and details shall be surveyed and provided
on the trackwork survey plans:
(i)
running edges of railway tracks and check rails to curves,
(ii)
wing and check rails to S&C, location of switch tips and
crossing noses of points, knuckles of diamonds, switch
types and angle of crossings
(iii)
positions of rail welds, insulated and non insulated rail
joints, adjustment switches, and twist rails,
(iv)
position of electrified conductor rails including feeder
cabling, hook switches with numbers and end ramps,
(v)
all cable ducting, cables and lineside equipment. (The
ownership and/or type shall be noted) eg posts, poles,
lightning columns, cable markers,
(vi)
signal gantries, posts and bases, and ground signals together
with signal numbers,
(vii)
a.c. electrification overhead line equipment gantries, masts,
stays and bases), together with structure numbers,
(viii)
track drains, manholes, culverts, ducts etc including invert
levels,
Specification
Land and Trackwork Surveys
(ix)
buildings, cabins, concrete or brick bases etc together with
an indication of any overhangs, canopies etc,
(x)
buffer stops,
(xi)
platform coper edge and any non moveable platform
furniture,
(xii)
overbridges - abutments, pier positions and numbers,
(xiii)
underbridges - parapets, centre girders (including heights
are to be clearly stated on the plot) wheel timbers, and
numbers,
(xiv)
both top and bottom of retaining walls,
(xv)
spot levels on areas of hard open ground at intervals not
more than 10 metres,
(xvi)
signalling equipment, point machines, pump
disconnection boxes, equipment cupboards,
manifolds, pressure vessels, valves,
(xvii)
switch heater units, including type, (gas, electric, strip,
cartridge, or pad) as applicable and controls,
(xviii)
any two levelling schemes within switch and crossing to be
noted.
units,
pipes,
Where structures are numbered, the structure number shall be
included on drawings of the trackwork survey.
Where datum plates are attached to structures, the location of the
datum plates, and the information shown on the datum plates shall
be included on drawings of the trackwork survey.
Further detail shall be surveyed to an accuracy of ± 75 mm
horizontally relative to adjacent features and ± (30 mm + 5 mm
/km) vertically relative to the nearest P.G.M.
(i)
level crossing surfacing system, cattle-cum trespass guards
and cattle grids,
(ii)
level crossing barriers or gates and operating equipment,
associated road traffic lights, signs and telephones,
(iii)
start and finish of transitions,
(iv)
mile, half mile, and quarter mile posts and gradient boards
with value,
(v)
approximate position of overhead power lines, telephone
cables etc and warning boards,
(vi)
top and bottom of earthwork slopes together with any
obvious change of slope and ballast profiles,
Specification
Land and Trackwork Surveys
(vii)
mature trees and areas of substantial vegetation,
(viii)
spot levels in areas of soft open ground, at intervals of not
more than 20 metres,
(ix)
Railtrack Zone boundary, fence lines, stiles, gates etc
together annotation of type where this is within 5 metres
from the nearest rail of any running line. Where the
boundary fence is more than 5 metres, the survey width
may be limited to that distance unless important or
relevant features, including the bottom of any
embankments, occur between the 5 metre distance and the
boundary fence in which case the survey shall be extended
to include such features,
(x)
footpaths.
The existing track type, eg C.W.R, jointed, flat bottom, bull head,
including type of fastening and sleepers shall be shown with the
extent indicated by arrows.
Names or roads, streets, railway buildings and structures, and
stations shall be shown.
(22.015)
Extent of
trackwork survey
16
All lines having independent alignments or which may be affected by
the proposed design shall be surveyed. Surveys shall extend a
minimum 50 metres and where practicable 100 metres longitudinally
outside the proposed track work sites shown on the Contract
Drawings. The survey shall extend out a minimum 3.0 metres
parallel to the nearest track.
Sufficient survey detail shall be taken to prove any reasonably
practical design scheme. Track cant, track intervals and clearances,
together with structure clearances shall be measured.
The baseline for tape surveys shall be located so that its alignment
can easily be replicated. Measured offsets exceeding 5.0 metres
shall be triangulated from survey pegs.
Surveys which would otherwise end within curving tracks shall be
extended clear of any transition curves. Curve survey information
shall be extended a minimum of the equivalent of two half chord
lengths into the adjacent straight.
Hallade schemes shall be tied into theodolite straights established as
part of the survey.
Where the limits of the proposed trackwork scheme is specified,
the existing rail depth shall be taken at the proposed rail break
points.
(22.016)
Specification
Land and Trackwork Surveys
Structures,
including bridges,
retaining walls etc
17
The survey shall note details of structure type, construction
materials and general condition, of the structure, parapets, roads
and footpaths and dimensions of main structural members. High
level detail shall be separately identified from the lower detail and
underground information. The survey interval for vertical and
horizontal clearances from rail to adjacent structures up to
20 metres along the tracks in both directions from the structure
shall be noted.
Clearances of the bridge girders, abutments and associated retaining
wing walls to bridges shall be physically checked by direct
measurement.
At high level the survey shall include road or track levels
information (centre and kerbs) cess or footpath levels (kerb and
parapet), kerb heights, details of utilities, parapets, pilasters, newels
and string courses.
At low levels the survey shall include abutments, wing walls,
buttresses, springing and soffit levels, (profile for arches), offset
distance of tracks and cable routes.
Surveys of bridges shall include six taped check dimensions to
abutment corners at road or rail level as applicable, and at springing
level or underside of bed course to the bridge deck as applicable.
The verticality of the abutment faces shall be recorded.
(22.017)
Trackwork and
trackside train
operating
equipment
18
The inter-relationship, including alignment of all trackwork and
adjacent infrastructure for a 50 metre distance from the structure
shall be surveyed. Sufficient detail shall be measured to enable full
cross sections at critical points to be drawn.
The location of all signalling and power supply equipment, cable
routes and ducting shall be surveyed and the position of a.c.
electrification overhead equipment and associated supports defined.
The survey shall be extended to the Railtrack boundary and include
platform detail, platform and bridge clearances, track formation
information and record the level of any adjacent water course.
(22.018)
Roads and
associated
information
19
The survey shall be sufficiently detailed to give accurate road profiles
and cross-sections along the route approaching and crossing the
railway and clearances to the fixed infrastructure. The distance to
be surveyed along the road shall be 40 metres on each side
approaching the Railway.
The survey shall record the following information:
(i)
road layout including kerb alignment, junctions, footpaths,
outline of buildings and fencing, and where applicable
entrances to adjacent properties,
(ii)
location of street lights, traffic lights, signs and other street
furniture,
Specification
Land and Trackwork Surveys
(iii)
manholes, gullies, stop cocks, vent pipes etc,
(iv)
utilities and overhead lines,
(v)
levels of roads at centre and kerbs, top of kerb, footpaths,
and centre of road and edge of footpaths across level
crossings,
(vi)
level crossing gates and operating equipment,
(vii)
earthworks, including embankment slopes,
(viii)
tree types and size within 3 metres of route, or as defined.
(22.019)
Trial holes for
undertrack survey
20
Where specified, trial holes shall be dug in accordance with
Section 215: Maintenance of Permanent Way to give under track
survey information or clearance dimensions between trackwork and
buried footings. The interval for the survey trial holes shall be at a
nominal 10 metre intervals along each track. The size of trial holes
shall be kept to a minimum to avoid any possibility of track
alignment distortion following excavation work.
(22.020)
Platforms and
underbridges to be
gauged
21
All platforms and underbridges with parapets or centre girders
above 100 mm from top of rail shall be physically gauged by direct
measurement in accordance with Railway Group Standard
GC/RC5504.
A Hallade scheme shall be undertaken with half chord points at
5 metre half chord intervals marked out and used as the datum
points during the survey.
Gauging of the platforms and underbridges shall be undertaken at
the half chord points and at bottom and top of platform ramps and
ends of bridge girders.
The location, extent and values of clearances of platforms and
underbridges below Standard as defined in Railway Group Standard
GC/RT5204 shall be recorded.
The type of construction and the overhang of the platform edge to
the platform wall shall be recorded.
The data shall be recorded in accordance with Railway Group
Standard GC/RT5204.
(22.021)