BIM Survey of a Heritage site

To scan or not to scan, and what actually is a BIM survey?

To scan or not to scan, and what actually is a BIM survey?
Recently we have been getting enquiries for 3D / point ‘cloud surveys’, ‘BIM surveys’ or ‘Revit Surveys’, with many customers needing us to help them clarify what they are actually looking to purchase.

To help you with this, I think the following may be useful:

All about Point Cloud Surveys
A kind of laser scanning technique, the point cloud survey price will differ depending on the building. A large empty warehouse, elevation or empty floor of a building can be collected very quickly via a point cloud with a minimal number of set-ups due to lack of obstructions. Conversely, a relatively small area of ‘active’ space such as a shop, office building or hospital could be very time intensive due to the number of rooms and items blocking the scanner ‘seeing’ into every corner.

Our experience has been that a good surveyor can be much quicker than a point cloud scanner in collecting enough information for the creation of a ‘traditional’ 2D floor plan. whereas a point cloud would be quicker on a complex building facade or on open areas. So it is important to gauge the reason for the survey and most cost-effective method of collection prior to commissioning a project.

Revit or BIM surveys
“Revit” or “BIM” surveys are difficult terms to quantify. As I’ve stated in previous blogs, Revit is an authoring tool and BIM a process, so these are really incorrect terms to use as survey types. Revit is a suite of products combining Architectural, Structural and MEP (mechanical / electrical / plant) flavours.

Each flavour of Revit creates a single discipline model (SDM) which combine to create a multi-discipline model or MDM. Therefore, to build a ‘proper’ MDM Revit model means collecting survey data (either traditional captured or via a point cloud) and understanding / recording which class of Revit library would apply to the data.

There is also the issue of hidden items such as HVAC and clad steelwork. To create a true Revit Model really requires an intrusive survey and ideally access to original plans if for instance, cable ducts/ HVAC/ steelwork are not visible to a surveyor (please see attached sample images illustrating different BIM survey levels possible).

There are many survey companies claiming to undertake BIM surveys who are just building 3D faces inside Revit to create an accurate ‘box’ – this is not a true BIM survey and is really no more useful than a traditional 2D survey containing height combined with a full set of photographs.

Below is our graphical representation of the different levels of BIM surveys

Graphical representation of BIM Surveys at level 1
Graphical representation of BIM surveys level 2
Graphical representation of BIM Surveys level 3