International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B2. Istanbul 2004 
difference, intensity and color information at several resolutions 
in a data pyramid. 
LasTools manages subblocks invisibly to the user, who may 
select any area (rectangular, polygonial or linear) within a block 
for display and processing and may pan and zoom the display 
freely over the entire block without having to work with 
subblocks or even encountering their traces in the displayed 
data. 
2.2 Workflow 
LasTools handles all steps of the lidar data processing workflow 
from project setup to output of products and provides guidance 
and support to the user on required steps, production progress, 
quality control, and report generation. 
The first step in the workflow is project preparation. It involves 
= setting up a project by defining its location in a computer 
environment, and creating the required directory structures 
(which happens automatically); a new project may be 
created from scratch or as a copy of an existing project if 
some of the parameters used in the old project also apply 
to the new project, 
= importing project-defining data (perimeters, target 
coordinate system(s) and projections, flight plans, 
products, output formats and tiling requirements, accuracy 
requirements, tie-points and control surface information, 
geoid, etc.), 
=» definition of the processing steps and timeline for 
processing milestones. 
In the second step the data to be processed is imported: 
= import of pre-processed trajectory data 
= import of raw or pre-processed lidar along with sensor 
description and calibration files — the import process 
includes geocoding of raw lidar data, generation of track 
outlines, conversion and storage of lidar data in the meta- 
data subblock files, 
= import of digital camera images and associated exposure 
location and calibration information. 
The next step covers lidar and image processing: 
" calibration — if not available from an earlier project 
LasTools assists in deriving sensor calibration parameters 
(sensor-specific parameters, boresighting, range- and 
angular offsets) for both lidar and simultaneously acquired 
digital camera data from a calibration flight pattern over an 
airfield, 
* strip adjustment using data from cross-track intersections 
and overlap of adjacent strips; adjustment of roll- and 
scanangle-scalefactor deviations is done using trajectory 
data, or if not available by an approximate reconstruction 
of the trajectory from strip data. The availability of track 
numbers as an attribute to each lidar point is, however, 
required. 
= verification of internal geometrical accuracy at strip 
overlap and intersection areas, 
=» classification of lidar points into classes ground/bare-earth, 
vegetation, buildings/artificial structures, etc., 
= control of classification quality by statistical analyses and 
visualization, 
* transformation into target system, 
= geometrical adjustment on the model level using reference 
surfaces, tie-points, and geoid data, 
= verification of absolute geometrical accuracy, 
834 
= generation of digital elevation models and lidar data 
imagery (IR intensity images, RGB/CIR images), 
"  Orthorectification of digital imagery using lidar DSM, 
mosaiking and tone balancing. 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
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data products report 
Figure 3. Workflow (gray=optional inputs) 
In the final step data products are output: 
= tiling, output conversion, and export in the required output 
formats (e.g. ASCII, LAS, Terrascan, Shape, GeoTIFF, 
JPG2000, etc.) 
= generation of a processing report, including documentation 
of performed processing steps, used parameters, input and 
output data files, time, and manpower, computing capacity 
spent to reach milestones and checkpoints, statistics and 
results of quality checks. 
2.3 Project Management 
The project management features of LasTools cover the 
following aspects: 
= user guidance, 
=" workflow and production status monitoring, 
" resource management 
= quality control. 
User guidance assists the user by indicating which actions are 
necessary for the production process to proceed, and ensures 
project integrity. This is especially valuable for a novice user 
who is advised which parameters need to be set (and what they 
mean), which files need to be imported and in which sequence 
processing should be done to achieve the desired results most 
efficiently. This is implemented in form of an advanced 
“project wizard”. Context sensitive online help functionality 
further assists users of all experience levels, ranging from brief 
“tool-tips” through more detailled item explanations to fully 
indexed user manuals and tutorials. 
Workflow control ensures that processing steps are performed 
in the required sequence and are completed before proceeding. 
The project administrator may define a sequence of processing 
steps and set certain conditions/milestones that must be met 
before subsequent steps can be initiated. It also controls access 
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