LiDAR integration in SURE

Introduction


Since version 3.0, SURE offers the possibility to use LiDAR data to improve the results both in the 2.5D workflow (DSM, True Ortho, DSM Mesh), as well as in the 3D workflow (3D Mesh). The use of LiDAR data is optional and the Dense Image Matching is completely independent from their provision. The LiDAR point clouds are meant as a complement to the Image data and prove to be particularly useful in situations where the geometry of the surface is difficult to reconstruct from images only, due to photogrammetric constraints (i.e. a Photogrammetry 3D point requires at least 2 lines of sight with no redundancy, while a LiDAR 3D point only requires 1 line of sight).

SURE remains a Surface Reconstruction software based on Dense Image Matching (DIM), making use of the advantages of this data source. Furthermore, there is the possibility of improving the results by adding LiDAR data.

Input / Formats / Requirements

Currently supported formats:

DataFormatIf LiDAR enabled, data is required in the processing steps
LiDAR point cloud filesup to LAS version 1.3 (LAZ supported as well)DSM and 3D Mesh
LiDAR trajectory fileSBET (.out)3D Mesh


LiDAR point clouds

SURE will use the first return points (first echo) of the LiDAR point clouds, in the idea that it stays consistent with an Image-based Surface Reconstruction product.

If the LiDAR point clouds have the noise points classified as such, then SURE will ignore those points. Otherwise, it is not necessary that the LiDAR input clouds are classified into other classes such as Ground, Vegetation, etc.


SBET Format

The SBET format (Smoothed Best Estimation of Trajectory) is a binary format describing the trajectory of the LiDAR data acquisition platform. Among others, it usually contains the positional information in the form Latitude, Longitude, Altitude in the WGS84 reference frame. Additionally, each data point contains the Time field, which is stored in week seconds. For more information, please consult the following source. 

Requirements


RequirementExplanation / Additional remarksRequired for the processing steps
The same coordinate system for LiDAR point clouds and DIM data
  • No adjustment or transformation operation is performed on the two data sources
  • Surface described by the LiDAR point clouds should "fit" well with the surface reconstructed from DIM
  • Inconsistencies of the surface features between LiDAR and DIM (e.g. like a building being represented only in one of the two sources) could lead to unwanted effects in those areas in the results.
  • DSM
  • 3D Mesh
Time information and Meta Time information contained in the LiDAR point clouds
  • Time Information: when the observation was taken for each of the points
  • Meta Time Information: bit field for GPS time set correctly according to the LAS format specification:
    • 0 for GPS Week Seconds
    • 1 for Adjusted Standard GPS Time
  • 3D Mesh
Specification of the correct Coordinate System of the DIM data
  • Necessary to bring the data from the LiDAR trajectory file into the same reference frame as the LiDAR point clouds
  • Can be provided indirectly through the orientation file (*.prj / *.gori), or directly by supplying the coordinate system *.wkt file during project setup
  • More info at Coordinate System article
  • 3D Mesh

Influence of LiDAR data


Data based only on DIMData based on DIM and LiDAR

Source: Leica - Bordeaux Oblique dataset (DSM)

Source: IGI - Betzdorf Nadir dataset (3D Mesh)

Source: Melk Nadir dataset (3D Mesh)

Key Features

Related topics:

Using LiDAR in SURE

Las format definition

Project Setup

Coordinate System

Project Area


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