What are LAS classification codes?

Numbers stored with each point in a LAS or LAZ file that say what the point is: 2 ground, 3–5 low, medium and high vegetation, 6 building, 7 low noise, 9 water, 17 bridge deck, 18 high noise and so on. They are defined by the ASPRS LAS specification; LAS 1.4 standardises codes 0 to 18.

What is the difference between class 0 and class 1?

Class 0 means the point was never run through a classifier. Class 1 means a classifier looked at it and could not place it in any other class. A scan that has never been processed usually has every point in class 0 or 1, so class filters have nothing to work with.

Can I filter a point cloud by class without desktop software?

Yes. IFC Viewer Online reads LAS, LAZ and COPC files in the browser and lets you show or hide classes 0 to 15, colour by class, and apply one-click recipes such as terrain (ground only, with contours) or removing vegetation and noise.

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Digital twins · 2026-10-03 · 9 min

LAS Point Cloud Classification Codes Explained (ASPRS 0–18)

Every point in a LAS or LAZ file can carry a class: ground, building, vegetation, water, noise. Those numbers decide what you can do with a scan — terrain models, scan-vs-BIM, clearance checks. Here is the full ASPRS table, what each code is for, and how to use them without desktop software.

LAS Point Cloud Classification Codes Explained (ASPRS 0–18) — IFC Viewer Online article cover

A raw point cloud is millions of points with a position and maybe a colour. A classified point cloud is millions of points that also know what they are. That one extra number per point is the difference between a pretty picture and something you can measure, model and check against.

The numbers are standardised by ASPRS in the LAS specification, and they are the same whether the file came from an airborne survey, a mobile mapping car or a terrestrial scanner that was later processed.

Table of ASPRS LAS 1.4 point cloud classification codes 0 to 18 with colour swatches: ground, low, medium and high vegetation, building, noise, water, rail, road, wires, tower, bridge deck — The ASPRS LAS 1.4 standard classes. Codes 19–63 are reserved; 64–255 are free for project-specific use.

Try it: a LAS scan next to its IFC

A LAS site scan of the Poblenou plot loaded with the pavilion model. Open the point cloud panel to colour it by class and toggle classes on and off.

LAS point cloud of a site loaded next to an IFC model in IFC Viewer Online — Scan and model ready

Key takeaways

Classification is one number per point, standardised by ASPRS: 2 is ground, 6 is building, 3–5 are vegetation, 7 and 18 are noise.
Class 0 means never classified; class 1 means classified as "none of the above". An unprocessed scan is all 0s and 1s.
Most useful operations on a scan — terrain, scan-vs-BIM, clearance — start by keeping some classes and hiding the rest.

The classes that matter most

Code	Class	Typical use
2	Ground	Terrain models, contours, cut-and-fill
3 / 4 / 5	Low / medium / high vegetation	Tree surveys; usually hidden for everything else
6	Building	Scan-vs-BIM, façade checks, massing
7 / 18	Low / high noise	Thrown away — reflections, birds, multipath
9	Water	Shorelines, drainage
10 / 11	Rail / road surface	Infrastructure surveys
13–16	Wires, towers, connectors	Power-line corridors and clearance
17	Bridge deck	Bridge inspection

Unclassified scans: the 0 and 1 problem

Terrestrial laser scans of buildings are very often not classified at all. Every point sits in class 0 or 1, and any filter by class either shows everything or nothing. That is not a fault of the viewer; the information is simply not in the file.

For building work you can often do without classes: a horizontal slice gives you a plan, a band over a slab gives you flatness, a section gives you a profile. Those operations use height, not class — and they work on any scan.

How those height-based analyses work is in floor plans, slab flatness and contours from a point cloud.

Using classes in the browser

Open the scan LAS, LAZ or COPC — together with the IFC, if you want to compare. Large clouds are streamed by level of detail, so you can start working before the whole file is loaded.
Colour by class The fastest way to see whether a file is classified at all: one colour everywhere means it is not.
Show or hide classes Classes 0 to 15 are individual toggles. Hide vegetation and noise, and the building and ground are left.
Or use a recipe Terrain keeps ground and draws contours at a sensible interval. Vegetation removes classes 3, 4, 5 and 7 in one click.

Putting the classified scan next to the model is covered in IFC and point clouds in the browser.

LAS Point Cloud Classification Codes Explained (ASPRS 0–18)