Point cloud file formats

[edit] Point Cloud File Formats

[edit] Introduction

The capture of existing building conditions through laser scanning for building design and construction or photogrammetry results in the generation of vast datasets. A point cloud is a linked set of millions of laser-scanned points that are purely geometric. These points map the physical location of surfaces but do not inherently possess semantic intelligence; a raw point cloud cannot distinguish whether a surface represents a wall, a duct, or a structural column.

To utilise this spatial data within a Scan to BIM workflow, the raw scan data must be exported, converted, and managed through specific file formats. The format delivered by a scanning provider dictates whether the data can be imported directly into authoring software, such as Revit, or if it requires an intermediate conversion and indexing step.

[edit] Primary Point Cloud Formats: Purposes, Pros, and Cons

The architectural, engineering, and construction (AEC) industry relies on several distinct file formats to store and transfer laser scan data. These can be broadly categorised into open standards, proprietary software formats, and legacy scanner-native outputs.

[edit] RCP and RCS (Autodesk ReCap)

RCP (ReCap Project) and RCS (ReCap Scan) are proprietary formats output by Autodesk ReCap. In practice, an RCP project file acts as an overarching directory that points to and links several individual RCS scan files together.

• Purpose: These are the default formats used when a project operates within the Autodesk ecosystem or when a surveying provider delivers native ReCap files.
• Pros: They offer the highest level of performance for direct linking into BIM software. Because ReCap spatially indexes the points within these files, they allow for a much smoother visual display when navigating heavy datasets.
• Cons: They are locked into a specific proprietary ecosystem. Maintaining data transfer efficiency often requires keeping individual RCS files under 5 GB or archiving the dataset into a zipped folder.

[edit] E57

E57 is an open-standard format officially designated as ASTM E2807.

• Purpose: It functions as the common interchange format generated by the majority of modern laser scanners.
• Pros: As an open standard, it ensures vendor-neutral data transfer between different stakeholders and surveying teams.
• Cons: The primary disadvantage is that it cannot be directly linked into certain authoring platforms like Revit. It necessitates an intermediate processing step where it must be indexed into an RCP/RCS format before it can be integrated into a BIM environment.

[edit] LAS/LAZ, PTS/PTX, FLS, and ZFS

These extensions represent a mix of scanner-native and legacy formats.

• Purpose: These formats are encountered when a surveying provider delivers the raw, unindexed output directly from the laser scanning hardware.
• Pros: They contain the unfiltered, raw data directly from the field, which can be useful for archival purposes or bespoke data processing workflows.
• Cons: None of these raw formats can be read or linked directly by standard BIM authoring software. They strictly require conversion and spatial indexing via software such as ReCap Pro to be transformed into RCP/RCS formats before any modelling can commence.

[edit] Data Conversion and Preparation Before BIM Integration

Before any file format can be integrated into a BIM environment, the raw data must undergo a rigorous preparation and conversion protocol. If the data is provided in E57, LAS, PTS, PTX, FLS, or ZFS formats, the following pre-BIM steps are mandatory:

1. Registration: Every individual scan position must be mathematically stitched together to form a single, unified coordinate system. If raw, separated scans are delivered, they must first be processed through registration software.
2. Cleaning: The raw file format will contain 'noise'—temporary objects such as people, vehicles, or equipment that moved during the capture process. This noise must be filtered out.
3. Indexing: The cleaned file is run through an indexing engine to convert it into a supported format (such as RCP/RCS), which spatially organises the data for efficient rendering.
4. Quality Verification: An intake check must be performed to identify duplicate points, misaligned scan patches, or areas lacking data coverage. Issues identified at this stage must be returned to the scanning provider for resolution before any elements are modelled.

[edit] Importing the Formats into BIM Software

Once the data is converted into a compatible format, it is integrated into the BIM environment following strict operational protocols.

[edit] Linking vs. Embedding

Data formats should be linked as external references rather than imported or embedded directly into the model. By linking the file, the central project model remains small and stable, while the heavy spatial data lives externally on the disk. In collaborative worksharing setups, linking a massive point cloud over a local network can cause severe latency; to mitigate this, it is standard practice to keep a copy of the cloud file on each individual user's local drive using a uniform relative file path.

[edit] Positioning Methodologies

The coordinate setup established during the linking phase becomes the permanent reference for all subsequent disciplines. Common positioning methods include:

• Auto – Origin to Origin: The standard default for scans utilising a local coordinate system. It places the origin of the point cloud file directly at the internal origin of the BIM project. Caution is required if the scans carry large surveyor coordinates, which can push the data far from the usable workspace.
• Auto – By Shared Coordinates: Utilised for georeferenced data formats that possess established survey control points.
• Auto – Center to Center: A method used strictly for quick visual assessments. It aligns bounding-box centres but lacks coordinate accuracy, necessitating manual repositioning later.
• Auto – Origin to Last Placed: Used when stacking multiple files from the same site to ensure consistency across separate data deliveries.

[edit] Scale and Coordinate Verification

Immediately after linking a formatted file, the position and scale must be verified in a 3D view. The cloud must sit correctly relative to the project geometry and origin. Scale is confirmed by measuring a known physical dimension captured in the scan—such as a window opening or column spacing—using internal measurement tools. If the scale or position is incorrect, the format must be adjusted, moved, rotated, or remapped within the link management settings before any drafting occurs.

[edit] References

• Point Cloud to Revit Model: How to Import, Model, and Convert Scan Data