Airborne Data Processing Software AddOn

RiHYDROfor commercial hydrographic and bathymetric surveying• Automatic classification of watersurface points• Generation of a water surface
model (WSM) based on classified
water surface points• Refraction correction of points
below the water surface model(WSM)• Support of different import andexport formats for classification
purposes• Use point clouds from different
scanners to identify water surfacepoints• Import externally generated WSM• Processes a large number of files
for unattended operation in batchmode• Smoothly integrated into RiPROCESSFor smooth processing of scan data acquired with RIEGL
Hydrography Laser Scanners the Airborne Data Processing
Software AddOn RiHYDRO is offered as supplement to RiPROCESS.
When processing bathymetric laser data, additional processing
steps have to be applied since both, the laser beam’s refraction at the air-water interface and the lower propagation speed
within the water column must be taken into account in orderto obtain a geometrically correct point cloud. Those specificprocessing steps – usually called “refraction correction” – haveto be carried out for each flight strip right after the standard ALS
processing workflow.
Refraction correction of the points below the air-water interface(i.e. both points on the water bed and within the water column)
requires a geometric Water Surface Model (WSM). WSMs canbe generated from the laser data by one of the tools offeredwith RiHYDRO. An alternative option is to import already existingwater surface models. In the first case, the water surface points
must be classified before. For this task, a specific point classification tool in RiHYDRO is provided, which allows classifying thepoints on horizontal water surfaces automatically.
The user can specify the index of refraction of the water andalso a depth bias value to be taken into account duringrefraction correction.

visit our website www.riegl.com

RIEGL Software

Data SheetRefraction Correction - Typical Workflow using RiHYDRO Tools
Classification of Water Surface Points
Profile view of classified water surface points

A tool for the automatic classification of water surface points is provided. Classification is based on identification of areas with layers of water
surface points and subaqueous points. From such areas the classification of water surface points is extended to the entire water body.
Classification can be checked and modified manually in critical areasprior to the generation of a water surface model. Classification by thirdparty software is supported.

Generation of Water Surface Model (WSM)
Maritime WSM visualized as normal vector field

Riverine WSM visualized as normal vector field

Based on the classified water surface points, a geometric water surface
model (WSM) is generated for each flight strip. For this task, a tool isavailable that allows the generation of a grid-based WSM containing
height (and – optionally – normal vector) for each cell. This tool may
be run in different modes, depending on whether standing water (sea,lakes) or riverine surfaces have to be handled.
Alternatively, already existing WSMs (i.e. generated by third-party software and given in a well-defined exchange format) may be imported
by another tool.

Shift of Targets Below Water Surface
to Correct Positions
Finally, the underwater targets have to be shifted to their correct positions according to refraction (beam bending and waveform compression). Therefore, a tool is available that is applied to each flight strip.
Based on the underlying WSM, for each relevant ray, a representative
plane is estimated and used to calculate the correction vector.
Optionally, all points, whose coordinates have been changed during thisstep, may be classified by this tool.
Refraction correction of targets below water surface

RIEGL
Laser Measurement Systems GmbH
Riedenburgstraße 48
3580 Horn, Austria
Phone: +43 2982 4211
office@riegl.co.at | www.riegl.com

Copyright RIEGL Laser Measurement Systems GmbH © 2020 – All rights reserved.
Use of this data sheet other than for personal purposes requires RIEGL’s written consent.
This data sheet is compiled with care. However, errors cannot be fully excluded and alternations might be necessary.

RIEGL USA Inc. | info@rieglusa.com | www.rieglusa.com
RIEGL Japan Ltd. | info@riegl-japan.co.jp | www.riegl-japan.co.jp
RIEGL China Ltd. | info@riegl.cn | www.riegl.cn
RIEGL Australia Pty Ltd. | info@riegl.com.au | www.riegl.com

www.riegl.com
Data Sheet, RiHYDRO, 2020-07-27