ArcGIS supports lidar data provided as LAS (or ASCII) files. There are three different formats (datasets) that can be used to manage and work with your lidar data in ArcGIS depending on your needs, which include the LAS dataset, terrain dataset, and mosaic dataset.
ArcGIS datasets that support lidar data
| LAS dataset | Mosaic dataset | Terrain dataset | |
|---|---|---|---|
| ArcGIS applications | ArcCatalog, ArcScene, ArcMap | ArcCatalog, ArcGlobe, ArcMap | ArcCatalog, ArcGlobe, ArcMap |
| Storage locations | File system | Geodatabase | Geodatabase |
| Relationship to LAS source files | Points to | Points to | None |
| Size limitation | Limited by space on disk | Limited by size allowed by geodatabase | Limited by size allowed by geodatabase |
| Surface constraints | Supported | Not supported directly(supported if present in LAS dataset or terrain dataset) | Supported |
| Lidar inputs | LAS files | LAS files, terrain datasets, LAS datasets | Multipoint feature class |
| Types of lidar | Airborne and terrestrial | Airborne | Airborne |
| Rendering | Points, triangulated surface viewed in 2D and 3D | Raster | Triangulated surface |
| Analysis | Tools that can ingest point clouds or TINs Use with 3D Analyst tools Use with LAS dataset tools Learn about analysis using LAS datasets | Use with tools that can ingest raster data Use with Spatial Analyst tools and other raster dataset tools Learn about analysis using raster data | Tools that can ingest TINs or raster datasets Use with 3D Analyst tools Use with Spatial Analyst tools and other raster dataset tools Learn about analysis using terrain dataset |
| Display | Thinned points Can change display by choosing different class types or data types Display is modified using the LAS dataset toolbar or the layer properties dialog box | Uses cache for faster display Can change display by choosing different class types or data types Display is modified using the layer properties dialog box or the Image Analysis window | Thinned points based on pyramids Can change display by choosing different class types or data types Display is modified using the layer properties dialog box |
| Editing points | Can edit the points residing in the LAS files | Cannot edit points | Can edit the LAS points as multipoints referenced by the terrain dataset |
| Combining with data | Supports LAS files, feature classes, and shapefiles | Supports LAS files, LAS datasets, terrain datasets, and other raster formats | Supports LAS and feature classes |
Using lidar as a LAS dataset
The LAS dataset provides fast access to large volumes of lidar and surface data without the need for data conversion or importing. It makes it easy to work with several thousand LAS files covering an entire administrative area or perhaps just a few LAS files for a specific study area. It allows you to examine LAS files quickly, providing detailed statistics and area coverage of the lidar data in the LAS files.
A LAS dataset can be:
- Used in ArcGIS in both 2D and 3D using ArcMap and ArcScene.
- Displayed as either points using elevation or point attribute renderers based on certain lidar filters applied to the point cloud.
- Rendered as a triangulated surface model.
- Visualized using elevation, slope, aspect, or contour lines based on certain lidar filters.
- Used to make updates to the source LAS files.
Many tools for the LAS dataset were designed for airborne lidar where surfaces are commonly interpreted from the point cloud. For example, with airborne lidar it makes sense to toggle on TIN based surface views or to interpolate raster DEMs. Terrestrial lidar, on the other hand, tends to be more immersive and is often only valid to view and use as a point cloud. ArcGIS doesn't know what kind of lidar you have so it's up to you to use it appropriately. For the most part, terrestrial lidar should just be used and viewed in ArcScene as points. The points can be used as a backdrop for digitizing measurements and features and be displayed in an integrated fashion with other GIS layers.
Learn about airborne and terrestrially collected lidar
Using lidar with the LAS dataset 3D View
Viewing LAS datasets using a 3D perspective is a great way to better visualize and understand the lidar data referenced by the LAS dataset. The LAS dataset 3D View window allows you to view your LAS dataset as points or as a surface in a 3D environment in ArcMap. The 3D view is only available from the LAS Dataset toolbar in ArcMap. 3D perspectives may make it easier to recognize particular features captured from lidar data, such as surface valleys, mountain peaks, buildings, vegetation types, forest canopy, road corridors, river/stream corridors, mines, construction sites, towers, and even power lines. Drawing these features in 3D allows you to validate your lidar data in GIS and enables you to make informed analytic decisions.
Using lidar with the LAS Dataset 2D Profile Viewer
A common way to visualize, analyze, and edit lidar data is to use a 2D cross-sectional view. A selected set of lidar points from a LAS dataset can be displayed and edited using the LAS dataset Profile Viewwindow accessed from the LAS Dataset toolbar in ArcMap. Visualizing cross sections of lidar data allows you to analyze collections of points from a unique perspective. 2D profile perspectives may make it easier to recognize particular features captured from lidar data, such as surface valleys, mountain peaks, buildings, vegetation types, forest canopy, road corridors, river/stream corridors, mines, construction sites, towers, and even power lines. Drawing cross sections of these features allows you to validate your lidar data in GIS and enables you to make informed analytic decisions.
Using the Profile View window, you can do the following:
- Measure distances and heights between points.
- Manually edit and update LAS classification codes.
- Manually edit LAS point-bit field flags.
- Display full-resolution lidar point sets.
- Select the LAS dataset 3D View
window to visualize the selected LAS dataset point set in 3D.
Editing LAS files
LAS datasets can be edited to make updates to the source LAS files or the lidar points in the source LAS files. LAS datasets can be edited to fix problems, make improvements, and increase or decrease the data area extent.
The list below includes common examples of how you can benefit from editing LAS datasets:
- Manually fix errors in class codes.
- Visually compare the lidar points against existing GIS data for data validation, such as building data.
- Classify lidar points using GIS features.
- Reclassify lidar points manually selecting one or many lidar points.
- Change entire classification codes currently in the LAS dataset.
- Add or remove LAS files from a LAS dataset to increase or decrease the data area extent.
- Add or remove other GIS surface features, known as surface constraints, to/from the LAS dataset.
- Interactively measure 3D distances between visible features, such as power lines and trees.
- Use the lidar points as backdrop data to digitize in new GIS features, such as street furniture.
- Assign a spatial reference to a project if necessary.
Using lidar as a terrain dataset
A terrain dataset is a TIN-based dataset that uses geodatabase feature classes as data sources. A triangulated irregular network (TIN) is a data structure used to model surfaces—such as elevation—as a connected network of triangles.
To add lidar (LAS files) to a terrain dataset, they are imported into a multipoint feature class in a geodatabase feature dataset. The terrain dataset is then generated within this feature dataset and can encompass much more than just the lidar data.
Terrain datasets will help you with the following:
- Represent and model the terrain of study areas by integrating 3D-based mass point observations with other data sources such as 3D features captured using stereophotogrammetry.
- Perform many types of 3D spatial analysis in your GIS using the ArcGIS 3D Analyst extension.
- Derive raster-based digital elevation models for use in modeling and analysis systems such as the ArcGIS Spatial Analyst extension.
Using lidar in a mosaic dataset
By adding your lidar data to a mosaic dataset, it can be used and rendered as a raster. This allows you to
- Use tools such as Viewshed, Contour, and Profile.
- Estimate volumes.
- Use it as a DEM.
- Use it to orthorectify imagery.
- Use it in applications that support rasters but not LAS files or LAS datasets.
The mosaic dataset is similar to the LAS dataset, in that it stores a pointer to the original dataset and does not move all the points from one format into another, therefore, being quick to create, small in file size, and easy to update with additional LAS files. Alternatively, you can convert your LAS files or LAS dataset to a raster dataset.
You can also use a mosaic dataset to catalog all your lidar data.