The package opalsQuality contains various modules and Python sub-scripts for checking the quality of ALS point clouds. The aim of this package is to get a simple and fast overview about the captured terrain data and their quality. Among the features of interest are:

digital surface models (DSM),
point density maps,
maps and histograms of height difference of overlapping flight strip DEMs for checking the relative accuracy,
tables and histograms of point/patch-wise diviations between ALS point clouds and independently measured control-patches to check the absolute accuracy
precision maps to estimate the level measurement noise of the captured data.

The final goal is to provide a professional basis for the checking and documentation of the quality of ALS data and for decision making on further pre-processing like strip adjustment.

Scripts and Modules of Package opalsQuality
Python Scripts	Description
opalsQuality.py	Package script providing a complete processing chain for quality assessment of ALS flight strips.
qltAccuracyPoint.py	Performs absolute accuracy checks for entire flight blocks w.r.t. to single (ground) check points.
qltAccuracyRegion.py	Performs an absolute accuracy check for entire flight blocks w.r.t. to reference regions (on the ground).
qltDSM.py	Derives surface models, shaded relief maps, and color coded hypsometric maps for a set of ALS strips.
qltDensity.py	Derives point density maps (color coded raster maps) for a set of ALS strips.
qltLSM.py	Calculates best fitting 3d-affine transformations between overlapping strip pairs.
qltStripDiff.py	Derives relative strip difference maps (color coded raster maps) for a set of overlapping strip pairs.
utilsImageOverlay.py	Script to combine a height coloring with a hill shading.
Modules	Description
Algebra	Provides a generic raster algebra calculator featuring mathematical, statistical and conditional operators.
Bounds	Derives and stores the 2D boundary polygon of a region covered by the point data of an ODM or the valid pixels of a raster.
Cell	Calculates statistical features of user defined attributes and stores them as raster models or rasterized point clouds.
Colorize
Diff	Calculates a difference grid model based on either two grids or a one grid and a horizontal reference plane.
Export	Exports vector data stored in an OPALS data manager (ODM) in various data formats.
Grid	Derives a 2.5D digital elevation models (DEM) in regular grid structure using simple interpolation techniques.
Histo	Derives histograms and descriptive statistics (min, max, mean, r.m.s, etc.) for ODM or grid/raster data sets and stores the results graphically (SVG) and numerically (XML).
Import	Loads vector and raster data into an ODM for subsequent use in modules dealing with point cloud and line related data.
Info	Extracts and reports information of an ODM, vector or raster file.
LSM	Estimates an affine 3D transformation to align overlapping ALS strip DEMs using Least Squares Matching.
Normals	Estimates local surface normal vectors for each point of a specific point cloud (ODM).
Overlap	Analyses a set of strip boundaries and determines all overlapping strip pairs.
Rasterize	Performs vector-to-raster conversion for all types of simple feature geometries (points, lines, polygons).
Shade	Derives shaded relief raster maps (geo-coded hill shading) of DEM grids.
Translate	Performs format conversion for vector data files with additional read support of GDAL rasters.
Vectorize	Performs raster-to-vector conversion and exports polyline geometries.
View	Provides an interactive 3d viewer for points (including arbitrary attributes) and lines.
ZColor	Derives color coded visualizations of grid models and stores them as geo-coded raster images.
ZonalFit	Fits geometry models to a set of data points for multiple regions-of-interest.