Lidar has
become an integral part of GIS mapping and analysis. Global
Mapper is well known for its ability to import, analyze, edit and export
Lidar datasets and other 3D point clouds. With Global Mapper Pro, advanced functionality
is leveraged through an easy to use Lidar
Toolbar. New
display options enables users to view points by height above ground to
visualize vegetation and building heights. Access to Global Mapper Pro
tools require a separate license1.
Lidar Data
Light detection and ranging (Lidar) mapping, sometimes called 3D laser scanning, is a method for gathering precise geospatial information on the shape and surface characteristics for a specific collection area. The method for collecting Lidar data produces very dense, large files that can be cumbersome to handle. Global Mapper Pro manages these large files with superior speed and efficiency.
Lidar data
is commonly delivered in two standard file format types: .LAS and .LAZ.
The LAS file format is a public file format for the interchange of 3-dimensional
point cloud, it is a binary file that retains the information specific
to Lidar data (unlike a generic ASCII). The .LAZ file format is a compressed
version of .LAS.
Importing Lidar Data
Importing Lidar data has been made easy in Global Mapper. Global Mapper offers native support for Lidar data. All ASPRS supported file formats (.las, .las, .gz, .laz, .tar, .gz, .tgz, .zip) can be directly imported through the Open Data Files option in the File Menu. There is also support for loading ESRI zLas files. After navigating to the saved file location and clicking open, the user will be presented with the Lidar Load Options dialog box. The Lidar Load Options dialog box enables users to filter and grid a point cloud prior to loading data into Global Mapper.
- ASCII Text
- ASPRS Lidar LAS Files
- BPF (Binary Point File) Lidar Format*
- Custom XYZ Grid
- E57 Lidar Point Cloud Format*
- ESRI Personal Geodatabase Format (MDB) Files
- Esri zLas Lidar
- GeoSLAM
- Global Mapper Package
- GvLF Lidar database format (.gvl)
- LandXML
- Leica PTS Lidar Point Cloud Format*
- Lidar Las (non asprs)
- Lidar LAZ (Compressed LAS) Files
- LizardTech MrSID MG4 Lidar
- PLY (Stanford Polygon Library)
- PTX (Cyclone)
- Recap .rcp / .rcs (Autodesk)
- TerraScan .bin/.ts Format
- XYZI
- ZFS (Z+F) Lidar
* Support for these formats requires Global Mapper Pro.
The formats listed in bold are also supported for export of point clouds.
Analyzing and Classifying Lidar Data
The
.LAS file format is a binary file format that maintains information specific
to a Lidar dataset, without being very complex. Files with
the extension named as LAS should conform to the American Society of Photogrammetry
and Remote Sensing (ASPRS) Lidar data exchange format standard.
Global Mapper has numerous tools for displaying and utilizing ASPRS Lidar classifications, which were created for use with LAS formats 1.1, 1.2, 1.3, and 1.4. Point classification present in a Lidar file can vary by LAS version starting with the Lidar Load Options which allows customized importation of the ASPRS defined point classifications listed below.
- 0 Never classified
- 1 Unassigned
- 2 Ground
- 3 Low Vegetation
- 4 Medium Vegetation
- 5 High Vegetation
- 6 Building
- 7 Low Point (Noise)
- 8 Model Key-point (mass point)
9 Water - 10 Railroad
- 11 Road
- 12 Overlap
- 13 Wire - Guard (Shield)
- 14 Wire - Conductor (Phase)
- 15 Transmission Tower
- 16 Wire-structure Connector
- 17 Bridge
- 18 High Point (Noise)
- 19 Overhead Structure
- 20 Ignored Ground (likely breakpoint proximity)
- 21 Snow
- 22 - 39 Reserved for ASPRS Definition
- 40 Bathymetric Point
- 41 Water Surface
- 42 Derived Water Surface
- 43 Submerged Object
- 44 IHO S-57 Object
- 45 No-Bottom-Found-At Bathy Point
- 46 - 255 Reserved for ASPRS Definition
For information about customizing the class designations, see Lidar Class Properties
Changing Existing Classification Codes
With Global Mapper Pro, you can manually classify Lidar points, in addition to using Lidar auto-classification tools on unclassified Lidar data. These classification tools are available in the Lidar Toolbar, and distributed throughout the application in various editing, load, and export menus.
Lidar data processing can also utilize the multiple return signals from each laser pulse. Intensity is a measure, if the number of Lidar returns generated for a single point. Most topographic Lidar systems record the intensity of the return pulse, measuring the strength of the return. The number of returns will be determined by the composition of the surface object reflecting the return.
The
Intensity values can be used to create an image, and are commonly used
in for identifying and classifying different ground features and can be
used as a substitute for aerial imagery.
Applying Classification Codes to Unclassified Lidar Data
Among the Lidar tools for editing classification, classification display and analysis are; Lidar Display, the Configuration Lidar tab. Additional options for advanced classification, and feature creation and analysis based on LAS elevation and intensity values are activated with Global Mapper Pro.
Feature Extraction from Lidar Points
Global Mapper also allows you to automate the process of locating features on the ground using Lidar data. These automated feature extraction tools are available with Global Mapper Pro activated.
Global Mapper Pro also allows you to do Custom Feature Extraction using perpendicular path profile views.