How to Evaluate Scan to BIM Companies Before Outsourcing Your Project

1 Introduction
2 Why AEC firms outsource Scan to BIM
3 What a Scan to BIM provider does
4 Factors to consider when choosing a Scan to BIM provider
5 Comparing Scan to BIM quotations
6 Evaluating proposals
7 Contract and delivery requirements
8 Conclusion
9 Related articles on Designing Buildings

[edit] Introduction

Scan to BIM is the process of using captured existing-condition data, such as a registered point cloud, to create a building information model. A point cloud records the measured location of visible surfaces, but does not inherently identify building elements, their function, construction history or design intent. These additional aspects must be interpreted from the available evidence and defined information requirements.

The quality of a Scan to BIM deliverable therefore depends on more than the appearance of the finished model. The survey data, modelling assumptions, required level of information, geometric accuracy, quality assurance procedures and treatment of areas that cannot be observed all need to be considered when selecting an external service provider.

[edit] Why AEC firms outsource Scan to BIM

Existing-condition surveying and modelling can create fluctuating workloads for architects, engineers, contractors and other organisations. Outsourcing can provide additional modelling capacity without requiring an organisation to maintain equivalent levels of staff, software licences and computing resources between projects.

Scan to BIM projects can also require specialist skills in areas such as point-cloud processing, survey registration, BIM authoring, parametric modelling, coordinate management and the interpretation of irregular existing conditions. The appropriate expertise depends on the type of asset and the intended use of the resulting model.

Outsourcing does not, however, transfer responsibility for defining the information requirements of the project. Before appointing a service provider, the client or lead organisation should establish what the model will be used for, what information is required, what accuracy is necessary and which aspects of the existing condition may not be observable.

[edit] What a Scan to BIM provider does

The scope of a Scan to BIM service can vary. A project may provide the service provider with an already registered point cloud, or the provider may also be responsible for survey planning, scanning, control, registration and data preparation. The procurement documents should therefore define clearly where the provider's responsibility begins and ends.

A typical workflow may include:

Input review: Point clouds, survey information, coordinate systems, units, datums and existing drawings are checked for completeness and compatibility before modelling begins.
Point-cloud preparation: Where required, scans are registered, cleaned and indexed so that they can be used efficiently for modelling.
Model creation: Building elements such as walls, slabs, doors, structural elements, ducts and pipes are modelled from the available evidence. The required modelling method and object type should be defined in the project requirements.
Information enrichment: Non-geometric information, such as room names, asset identifiers and system classifications, should be added only where it is supported by reliable information or has been specifically defined as an assumption.
Quality assurance and delivery: The model is checked against the point cloud and other project information before the agreed native and exchange-format files are issued.

A point cloud does not automatically produce a complete or authoritative BIM model. Modellers have to interpret the captured information and make decisions about how to represent irregular geometry, partially observed elements and discrepancies between the point cloud and other available records.

[edit] Factors to consider when choosing a Scan to BIM provider

Relevant experience should be assessed against the proposed project rather than simply the number of years a provider has operated. Experience with similar building types, disciplines, survey conditions, model uses and levels of complexity can be more relevant than general experience.

Team competence is also important. The procurement process can identify the people who will undertake and review the work, their relevant experience and the arrangements for maintaining continuity if key personnel become unavailable.

The intended purpose of the model should be defined before specifying the modelling requirements. Terms such as Level of Development (LOD) describe aspects of the development of model elements, but LOD should not be used as a substitute for a project-specific description of the information and geometric requirements. Designing Buildings describes LOD as relating to the extent to which the geometry, specification and associated information of a model element have been developed.

Accuracy should be specified separately from model development or visual detail. The USIBD Level of Accuracy framework, for example, uses defined accuracy levels specified at a 95% confidence level. Accuracy requirements should be selected according to the intended use of the information rather than assuming that the highest available accuracy is necessary for every element.

The treatment of occluded or inaccessible areas should be explicitly defined. A point cloud records surfaces that have been captured and does not establish the condition of elements that cannot be seen. The model should therefore distinguish between observed information, information derived from other reliable records and assumptions. A gap or assumptions register can be used where appropriate.

The workflow should be documented sufficiently to establish responsibilities, information requirements, milestones, review procedures and change control. A project-specific BIM Execution Plan can provide a framework for defining how the required information will be produced and delivered.

Quality assurance should include an appropriate level of independent checking. This may involve checking model geometry against the point cloud, reviewing model content against the information requirements and recording issues and corrective actions.

Interoperability should also be considered. The required native authoring-software version, exchange formats and model templates should be agreed before production begins. Where IFC or another open exchange format is required, a sample exchange can be used to establish whether the information survives the transfer as intended.

Information security is relevant because point clouds and BIM models can contain detailed information about buildings, access routes, plant and other potentially sensitive features. The contractual and technical arrangements should address matters such as access control, data storage, transmission, retention, deletion, subcontracting and any applicable data residency requirements.

Capacity and communication arrangements should also be established. The project should identify the principal contacts, review and approval procedures, expected response times and arrangements for dealing with changes or additional information.

[edit] Comparing Scan to BIM quotations

Quotations should be based on sufficiently consistent information that the scope and deliverables can be compared. A quotation request can identify the buildings and floors included, point-cloud size and format, disciplines and elements to be modelled, required software versions, information requirements, accuracy requirements, exchange formats, delivery stages and the number and nature of review cycles.

Price alone may not provide a meaningful comparison. Two quotations with apparently similar prices can have substantially different scopes, assumptions, accuracy requirements or levels of checking. The evaluation should therefore consider the complete scope of work, deliverables, exclusions, programme, quality assurance arrangements and any potential additional costs.

A pilot exercise can be useful for complex projects. Where appropriate, the same representative sample can be provided to shortlisted providers and assessed against predetermined acceptance criteria. The sample should include the types of conditions that are likely to present difficulties, such as irregular geometry, occluded areas and congested building services.

The pilot should be treated as a test of the specified requirements rather than simply a visual comparison of models. It can assess geometric accuracy, model content, assumptions, interoperability, file structure and the effectiveness of quality assurance procedures.

[edit] Evaluating proposals

An evaluation framework can help ensure that the same criteria are considered for each proposal. Possible criteria include:

Relevant experience with comparable assets and project requirements.
Competence and experience of the proposed project team.
Understanding of the information requirements and intended model use.
Proposed geometric accuracy and validation methodology.
Treatment of occluded, inaccessible and uncertain information.
Modelling methodology and BIM Execution Plan.
Quality assurance and independent checking arrangements.
Interoperability and required file formats.
Information security and data governance.
Capacity, programme and communication arrangements.
Commercial terms, scope and total cost.

The relative importance of these criteria should reflect the risks and intended use of the project. For example, accuracy and validation may be particularly important where the model will support detailed refurbishment or building-services coordination, while information security may require additional attention for buildings with sensitive operational information.

Evaluation records should identify the evidence supporting conclusions about each proposal. This makes the procurement process more transparent and helps establish which assumptions and requirements formed the basis of the appointment.

[edit] Contract and delivery requirements

The requirements established during procurement should be carried into the contract and project documentation. These can include the model purpose, scope, information requirements, accuracy requirements, coordinate system, assumptions, exclusions, deliverable formats, review procedures, acceptance criteria, programme and responsibilities.

The contract should also establish how changes to scope will be managed. This is particularly important where additional survey information or modelling is required because existing conditions differ from the information available at the beginning of the project.

Ownership, permitted use and responsibility for the point cloud, model and associated information should also be addressed. Where information is exchanged through a common data environment, responsibilities for submitting, reviewing, approving and retaining information should be defined. A common data environment provides a managed source for collecting, managing and disseminating project information.

[edit] Conclusion

Selecting a Scan to BIM provider requires assessment of the complete information workflow rather than simply the appearance or price of the finished model. The intended use of the model should be established first, followed by clear requirements for scope, information content, geometric accuracy, assumptions, interoperability and quality assurance.

A representative pilot can provide additional evidence of a provider's ability to meet those requirements, particularly for projects involving complex existing conditions. The resulting acceptance criteria, assumptions and validation requirements should then be incorporated into the project documentation and contract.

When these requirements are defined clearly, outsourcing can provide additional modelling capacity while maintaining a structured approach to the quality and reliability of the resulting information.