Every proposed building or structure should be properly set out by survey in accordance with the design plans, hopefully provided in digital format. If instructing firstly have a look at those links relating to Survey Fees, Terms of Contract and Survey Methology. A request to Dial Before you Dig should also be made.
SETOUT SURVEYS: What is required by the Surveyor for efficient and cost effective setting out?
In this digital world most requests to setout design structures involve digital data.
THE IDEAL SITUATION IS FOR THE ARCHITECT, BUILDER OR INSTRUCTOR TO PROVIDE A 'LAYER', PLAN OR SKETCH of ONLY those lines that are to be setout and offsets to boundaries. This saves an incredible amount of office time.
The Surveyor is usually the first one on the ‘scene’ of a proposed new development, whether it be a subdivision, major road works, bridges or simply a house, the surveyor is asked to undertake a Detail or Feature Survey to provide the Engineers or Architects with a ‘map’ of the location and those physical features that need to be considered when designing the new structure.
Sometimes, an architect becomes involved with a site after a development has taken place and has access to Design Engineering Plans. In relation to the physical features of the site, one should NEVER, EVER, EVER USE SUCH information to undertake design work (it may well be of use in relation to the Building Design but not Civil Engineering matters); One should ALWAYS SEEK an actual As Constructed Survey (a fresh Detail Survey) of the site to be developed. Earthworks and roads rarely reflect the design intent.
Invariably the surveyor will undertake this survey on Australian Height Datum (AHD) and Map Grid of Australia (MGA). In some rare cases in the past (pre GPS days) the survey could be on an Arbitrary Datum due to lack of availability of Survey Control (available State Marks that provide AHD & MGA). This should no longer be the case and the instructor should demand AHD/MGA.
Whatever the Datum adopted by the Surveyor, there is a preference that this data not be ROTATED, RE-SCALED or 'SHIFTED' by others who follow in the design process.
A reasonable proportion of the Engineering profession in Tasmania stick to this concept, as like surveyors they work in metres and not mm as do Architects. Quite often Architectural Plans are shifted, rescaled and rotated.
The desirability of not shifting the data is that it is subsequently used to setout works, whether by a surveyor or contractors using gps or other new technology. Whilst it is possible for the setout person to Re-rotate, Shift and Scale, this defeats a lot of the advantages of digital data usage and creates additional costs and introduces a further source of error.
If possible data should not be relocated or shifted away from the original survey datum, as nearly always it is a requirement that all drawing files are to be positioned in the correct location by multiple consultancies such as architects, building designers and engineers. The setting out position should remain constant throughout the project. If the external contractor or consultant moves the survey data from its original insertion/origin point (datum) to undertake their work, then these shifts should be reversed at the time of production of final documentation for setout or coordination purposes.
To avoid problems with overlaying information the drawing rotation in CAD 'model space' must never be altered.
Upon receipt of the Architects or Engineers site layouts the surveyor will overlay this information onto the original Detail Survey datum to check for general continuity. If it is necessary to Re-ROTATE, RE-SCALE or 'SHIFT' to refit over the original Survey datum additional costs will be incurred contrary to the clients interests. As it is an understanding that sometimes data must be at the least re-scaled, we would think the inclusion of a Grid in the Survey Data that is carried through to the final Architectual Setout Plan is a big step towards assisting with this issue. Architectual feedback to this web page seems to indicate that if data is X-referenced by the Architect then this issue should not arise.
Detail & Feature Surveys produced by this office carry a note advising
*** ATTENTION CAD USERS ***
ENGINEERS, ARCHITECTS, DRAFTSMAN
If your design is to be the subject of a setout
you generate additional costs for our mutual client
at setout if you
ROTATE, RE-SCALE or 'SHIFT'
this digital data.
If you must do any of the above, ENSURE
that the GRID shown on the data is
carried forward in all of your digital data & if
'turned off', forms part of any setout digital data
you may issue. If not digital, ensure the
setout is connected to the grid by dimensions
POINTS TO CONSIDER:
These are listed so that a better understanding of the next section, 'WHAT IS IDEAL FOR THE CLIENT AND SURVEYOR AT SETOUT', is gained
- It is my understanding that those using ‘AutoCAD’ type software (or software that outputs in dwg’s, as a standard output) can deal with the re-scale, shift and rotate issue "by X-referencing. Only in the older versions of this type of software is it an issue to be forced to ‘stay with’ the surveyor’s datum".
- Additional data or changes to designs are a nightmare for the setout surveyor if they have been produced on shifted datum. Instead of being a simple integration of new data with the old, a two minute process, they become a convoluted process fraught with error possibilities.
- All Survey Data consists of a set of points of known X, Y & Z co-ordinates (or in layman’s terms longitude, latitude and height). These points are joined by lines, often called strings (points can exist by themselves with no strings attached!). So the data set consist of points and strings of known X, Y & Z co-ordinates. These items are known collectivly as 'objects' with 'Attributes' (X,Y & Z, a description, colour etc). Usually, the Engineers or Architects CAD data is not in 'points & strings' format, but in ‘plines’, lines without points with attributes at each end. Engineers or Architects CAD data is therefore in plines & blocks and can include reference files (we will not go here today!).
- Survey data does not usually include ‘Blocks’, a ‘picture’ of a feature that is one single object and not a group or set of plines; a bit like an emoji on one’s iPhone. Architectural & engineering plans quite often use blocks for features that are repeated, such as a Side Entry Pits (SEP), beds, cars etc. If a feature is shown as a Block it is not possible to ‘pick’ a corner or centre of it or use it for calculation of setout points unless it is ‘exploded’ into its elements (bits & pieces); the exploded Block remains as plines.
- Survey Cad packages allow for the conversion of plines to points and strings. However, Blocks need exploding first before conversion. Upon conversion, an exploded block can produce many many points & lines, especially around curves (a car or SEP for example will end up as many points & lines). For the Surveyor doing calcs for a Setout this again can be a nightmare of data points often with his required setout point in amongst the numerous points (SEP's are quite often needed for setout of kerbs).
- Detail or Feature Surveys advise on the source & degree of accuracy of any boundary lines compiled into the survey information. If setouts are a required distance off a boundary or on a boundary, then an ‘official’ re-establishment of that boundary is required. A Boundary Remark Survey may be required. This quite often can be the biggest cost of a setout survey.
- Be aware what a “Sketch By Way of Illustration” title is. The title dimensions SHOULD NOT be relied upon. Read what this means in terms of Strata Development and Boundary Entitlements
- A lot of set outs now involve shapes and structures that are very hard to check against a ‘Paper Plan’. Digital data is the only way to set them out. However, the Surveyor will or should advise the instructor that:
“Interpretation of Architectural Plans falls outside a Surveyors area of expertise.
It is the instructor’s responsibility to check those dimensions shown on this plan
or request Digital Information and check same by Digital Overlay. If the setout
is derived from Digital Data supplied by the design draftsperson via email, the instructor
should confirm this setout with the design draftsperson by digital overlay”
The biggest source of error with instructions to Setout is the difference between what an instructor BELIEVES is being setout as compared to the Surveyors interpretation of what he has setout or is going to setout. (ie the surveyors understanding of instructions given). It is essential that the instructor understands that HE the instructor (not the surveyor) is taking responsibility for what actual points are setout. The Surveyor takes responsibility for setting out these points or lines in accordance with their relationship to each other as shown on the Setout Plan produced by the surveyor, not interpreting architectural plans drawn by others. It is not enough for the instructor to 'leave it to the surveyor to sort out'. Once the instructor has clearly identified what points and lines he requires, the surveyor can produce setout data reflecting his interpretation of these items for the instructor to confirm.
WHAT IS IDEAL FOR THE CLIENT AND SURVEYOR AT SETOUT.
Do not ROTATE, RE-SCALE or 'SHIFT' survey data unless it is X-referenced
For Setout, provide a DWG drawing on survey datum
A single setout LAYER produced by the designer showing those points to be setout.
Preferably as points and strings with LEVELS on the points (usually a centreline of a road or road edge, but can apply to design of a house)
IMPERATIVE that reference points created by the surveyor in his Detail Survey are carried forward into the design drawings. Carry through to setout any Grid provided on the survey data.
IMPERATIVE that the horizontal and vertical datum are advised on the setout data.
Preferably with dimensions and offsets to boundaries.
DISCLAIMERS THAT MAY BE USED WITH DETAIL, FEATURE, CONTOUR OR SETOUT SURVEYS
WHILST REASONABLE EFFORT HAS BEEN MADE TO
LOCATE ALL VISIBLE ABOVE GROUND SERVICES,
THERE MAY BE OTHER SERVICES WHICH WERE NOT
LOCATED DURING SURVEY.
PRIOR TO ANY DEMOLITION, EXCAVATION OR
CONSTRUCTION ON THE SITE, THE RELEVANT
AUTHORITY SHOULD BE CONTACTED FOR POSSIBLE
LOCATION OF FURTHER UNDERGROUND SERVICES
AND DETAILED LOCATIONS OF ALL SERVICES.
THIS NOTE IS AN INTEGRAL PART OF THIS
THE INSTRUCTOR SHOULD SATISFY HIMSELF
CONCERNING UNDERGROUND SERVICES. HE
SHOULD CONSULT WITH SERVICE PROVIDERS
INCLUDING BUT NOT RESTRICTED TO AURORA,
THE WATERBOARD, TELSTRA & THE LOCAL
AUTHORITY TO ENSURE THAT THERE ARE NO
ADDITIONAL UNDERGROUND SERVICES OR
SERVICES NOT REFLECTED BY REGISTERED
EASEMENTS. NOT ALL SERVICES HAVE EASEMENTS
REGISTRATION OF THE BOUNDARY
DEFINITION UNDERTAKEN RELATING
TO THIS SITE IS RECOMMENDED TO
ENSURE THAT 'OTHERS' GIVE DUE
CONSIDERATION TO THE BOUNDARY
DEFINITION ADOPTED AND THE REASONS
FOR SUCH ADOPTION. YOU SHOULD
MAKE YOUR ARCHITECT, ENGINEER &
BUILDER AWARE OF THIS RECOMMENDATION.
IF BUILDINGS ARE TO BE BUILT ON OR NEAR
A BOUNDARY, THEN SUCH REGISTRATION IS
HIGHLY RECOMMENDED & FURTHER
SUCH BUILDINGS SHOULD BE SETOUT
BY A REGISTERED SURVEYOR. STRATA
BUILDINGS OVER BOUNDARIES MUST BE
DEMOLISHED OR ADDITIONAL LAND
Whilst reasonable effort has been made to locate all
visible above ground services, there may be other services
which were not located during survey. This survey does not
include a 'Dial Before you Dig' enquiry. This survey is
a General Detail Survey undertaken to 'Detail' accuracy. If detail is
required to an accuracy greater than General Detail Surveys
then the instructor should advise accordingly. For example, if wall
or building locations are to be utilised for construction purposes,
we should be advised accordingly.
The title boundaries shown on this General Detail Plan were
not marked at the time of survey and have been determined by
existing title plan dimensions & occupation (where available) only
and not by field survey. As a result they are considered
approximate only. This plan should not be used for building to
boundary or to prescribed set-backs without further survey.
If Strata Subdivision over this site is contemplated all buildings
existing or resulting from the development must be within the
title boundaries. A registered Remark Survey is recommended
at this time. Services shown have been located where possible
by field survey. Prior to any demolition, excavation or construction
on the site, the relevant authority should be contacted for
possible location of further underground services
and detailed locations of all services.
This plan may not be copied unless this note is included.
THIS PLAN HAS BEEN PREPARED
FROM COMPILED INFORMATION
HELD WITHIN THIS OFFICE AND
IS NOT THE RESULT OF A NEW
FIELD SURVEY. IT IS PRODUCED
UPON REQUEST WITH THE
RECIPIANT BEING AWARE THAT
TITLE AND FIELD INFORMATION
SHOULD BE RATIFIED.
THIS PLAN MAY NOT BE
COPIED UNLESS THIS
NOTE IS INCLUDED.
INTERPRETATION OF ENGINEERING DIGITAL PLANS FALLS
OUTSIDE A SURVEYORS AREA OF EXPERTISE.
CERTAIN ASSUMPTIONS HAVE BEEN MADE IN DETERMINING
THE IDENTITY OF ENGINEERING DIGITAL LAYERS.
IT IS THE INSTRUCTORS RESPONSIBILITY TO
ENSURE THAT THE DIGITAL DATA WITHIN THIS SETOUT PLAN
REFLECTS THOSE POINTS THAT HE WISHES SETOUT. IT MAY
BE NECESSARY FOR THE INSTRUCTOR TO FORWARD THIS DATA
TO HIS CONSULTING ENGINEER FOR CHECKING OF THE SETOUT.
I ...................................CONFIRM I HAVE CHECKED THIS SETOUT
DATA AND IT REFLECTS MY WISHES & INSTRUCTIONS.