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Geo-Referencing

What is Geo-Referencing?

It is to define the geographical location of the BIM model, by assigning real-world coordinates to it.

 

According to BCA’s Code of Practice (Ver. 1 2016),

The development and all its elements should be geo-referenced to global coordinates from the Singapore SVY21 coordinate system (EPSG: 3414) for Easting and Northing (x, y) and Singapore Height Datum (SHD) for Height (z).
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A correctly geo-referenced location thus contains the project’s base point and survey points in SVY21 coordinates including dimensions between grids.

The layout of the site model shall be presented in True North or real-world orientation. Elevation levels of the model shall be set up based on the Singapore Height Datum (SHD) of 0.000m.

 

Why is there a need to geo-reference BIM models?

Standardising the geo-referencing of BIM models to the SVY 21 coordinate system and the Singapore Height facilitates geospatial analysis and retrieval of relevant site information and data for Agency regulatory checks.

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How do I geo-reference my BIM model?

Learn more about how to input coordinates to your model in your native BIM software:

Geo-Referencing Revit Files


Revit does not have an in-built global coordinate system, so specifying coordinates and having a geo-referenced linked file with shared coordinates may be needed to set more accurate survey point(s) that provide a real-world context to the Revit model.

Method 1: Specify Coordinates


If you know the SVY21 coordinates that a certain point in the model is supposed to correspond in the real-world:

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Use ‘Specify Coordinates at Point’ tool: Select a reference point in the model and specify the correct [X]-Easting, [Y]-Northing, [Z]-Elevation coordinates and Angle to True North for it. The model’s coordinates and Project Base Point will then be adjusted accordingly to reflect their proximity to the reference point. See here for guide.


Method 2: Linking a CAD/ DWG file and acquiring the coordinates


If you have a CAD/ DWG file of the site which has already been geo-referenced to the real world:

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Via ‘Acquire coordinates’ tool: Link a site DWG file and acquire its coordinates for geo-referencing. See here for guide and here for a tutorial video.
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Geo-Referencing ArchiCAD Files


See full step-by-step guide for ArchiCAD 20 to 24 here. Refer to Section on ‘Storeys, Project Location and Reference Levels’.



Method: Setting up Project Location and True North


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Go to ‘Options’, choose ‘Project References’ and ‘Project Location’’: Input the Latitude, Longitude and Altitude for the model’s [X], [Y] and [Z] coordinates, and specify the angle for Project North.
Note:
  • To convert your project’s Northing and Easting to Latitude and Longitude, you may use reliable web tools (E.g. Montana State University’s Converter).
  • For Altitude, you may enter in SHD form (eg, For SHD 104, enter 4 into Altitude).
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Geo-Referencing OpenBuildings (formerly AECOsim) Files


See step-by-step tutorial here.




1-pic-1Method: Setting Geographic Coordinate System


1Go to ‘Coordinate System’ and select SVY21 under Singapore’s library

2Link all reference files (.dgn) relevant to the project

3Specify the real-world site coordinates for all the reference files in the ‘References’ pop-up window, in the offset X, Y, Z boxes.
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Other Resources

BCA Guidelines

BIM e-submission guide, including geo-referencing requirement. See here (pg 7).

General

Learn more about geodetic systems for geo-referencing. See here.

SVY 21 Coordinate System

Find out more about the SVY 21 coordinate system. See here.

One Map’s API for converting to SVY 21 coordinates. See here.

 

For any feedback or enquiries related to CORENET X, please complete the form here.

 

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