Glossary
3D Scanning, BIM and Surveying Terms, Explained
Plain-English definitions of the terms you will hear on scanning, layout and survey projects, from point clouds and LOD to RTK and GPR. Written by the team at Datum Tech Solutions, a Leica Geosystems Authorized Service and Distribution Partner.
As-built
Documentation of how a building or site actually exists, as opposed to how it was designed. Laser scanning is the fastest way to produce accurate as-builts.
BIM
Building Information Modeling. A 3D model where each element carries data (type, size, system, material) used for design, coordination, construction and facility management.
Calibration
Checking and adjusting an instrument's errors (such as collimation and tilt axis on a total station) so its measurements stay within the manufacturer's specification.
Construction layout
Transferring design points (gridlines, anchors, sleeves, hangers) from the model to the jobsite, typically with a robotic total station or GPS rover.
3D laser scanning
A laser scanner measures millions of points on every surface around it by timing reflected laser light. The result is a point cloud that records existing conditions far faster and more completely than tape or total station measurements.
Digital twin
A digital replica of a physical asset that is kept current, usually built from scan data and BIM, used to plan changes, operate facilities and preserve history.
GNSS / GPS
Satellite positioning. GNSS covers all constellations: GPS (United States), GLONASS, Galileo and BeiDou. Using more satellites means better coverage near buildings and trees.
GPR (ground penetrating radar)
Sends radar pulses into the ground or concrete and records the reflections to locate buried objects, including non-metallic pipes, voids, rebar and post-tension cables.
LOD (Level of Development)
How much detail and reliability a model element carries. Common levels: LOD 200 (approximate size and location), LOD 300 (specific size, shape and location), LOD 350 (adds connections to other systems), LOD 400 (fabrication detail) and LOD 500 (field verified).
Network RTK
RTK corrections delivered over the internet from a network of permanent reference stations, so you do not have to set up your own base. HxGN SmartNet is the network RTK service from Hexagon, Leica Geosystems' parent company.
Point cloud
The set of 3D points a scanner captures. Each point has X, Y and Z coordinates, usually with intensity or color. Point clouds are the raw material for models, drawings, clash checks and measurements.
Point cloud file formats
E57 is the open, vendor-neutral exchange format. RCP and RCS are Autodesk ReCap formats used by Revit and AutoCAD. LGS and LGSx are Leica formats that open in TruView. LAS is the standard for lidar and drone data. PTS is a simple text format.
Prism
The reflector a total station measures to. Circular prisms are aimed at the instrument. 360 degree prisms can be measured from any direction, which suits robotic work.
Reality capture
The umbrella term for recording physical conditions digitally: terrestrial laser scanning, mobile and handheld scanning, photogrammetry and drone capture.
Registration
Aligning many scan setups into one point cloud. Software matches overlapping geometry (cloud to cloud), scan targets or survey control. In the Leica workflow this happens in Cyclone REGISTER 360.
Relative vs absolute accuracy
Relative accuracy is how well points agree with each other inside the point cloud. Absolute accuracy is how well they match real-world project coordinates, which depends on survey control. Both matter for survey-grade work.
Revit
Autodesk's BIM software and the most common target for scan to BIM. Leica CloudWorx for Revit lets Revit users work with Leica point clouds directly inside Revit.
Robotic total station
A motorized total station that locks onto and follows a prism, so one person can run it from the pole with a controller. Leica's construction line is the iCON robot.
RTK
Real-Time Kinematic positioning. A GNSS rover receives corrections from a base station to get centimeter-level positions in real time, which is what makes GPS useful for layout and survey.
Scan target
A black and white checkerboard or sphere placed in the scene. Targets help register scans together and connect them to survey control.
Scan to BIM
Turning a point cloud of existing conditions into a BIM model, most often in Revit, so designers start from what is actually built instead of old drawings.
SLAM
Simultaneous Localization and Mapping. It lets mobile and handheld scanners such as the Leica BLK2GO track their own position while moving, building the point cloud as you walk.
Survey control
Points with known coordinates, set by a surveyor, used to tie scans or layout to the project coordinate system so everything lines up with the design.
Total station
A survey instrument that measures horizontal angles, vertical angles and distances to calculate the 3D position of a point. Used for surveying, construction layout and as-built checks.
TruView
Leica's free viewer for scan data. Each scan setup opens as a 360 degree panorama backed by the point cloud, so anyone can look around, measure and mark up with no CAD skills.
Utility locator
An electromagnetic tool that finds metallic utilities, or tracer wire, by detecting the signal they carry or one applied by a transmitter. Often used alongside GPR.
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