Geotechnical Investigations Using QGIS Software

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Geotechnical practitioners typically use a variety of software tools during investigations, including Geographical Information Systems (GIS). While the value that GIS brings to the investigation is generally accepted, many practitioners do not know how to use this technology themselves. The fully subscribed GIS for Geotechs courses run by myself over the last 4 years, proves there is strong interest amongst our community in Australia and NZ to improve this situation. The GIS course I run uses an open-source product called QGIS (or Quantum GIS), that has an advantage for the registrant of not needing to purchase a license and which can be installed on private (or corporate) computers, running natively on 3 major operating systems. QGIS has become very popular world-wide for a variety of applications, has excellent online resources and the pace of development is staggering! In the last few years, I have increasingly used QGIS for my routine work. The purpose of this presentation is to demonstrate workflows I developed to solve particular problems using QGIS. Besides the use of GIS software, these workflows also include other tools such as spreadsheets, databases, drillhole software, structure from motion software, digital stereoscopes, etc. For those wishing to improve their generic GIS skills or just spectators, I am hoping my webinar will demonstrate what is possible with these tools. For those already expert in GIS (regardless of what software solution you use), I am hoping the examples will be of interest, as every project poses a unique set of challenges to overcome, and there can be many ways to solve these. The examples I present will be based around three recent projects I have been heavily involved in:

  • regional landslide susceptibility mapping for planning applications
  • linear risk-assessment along a tourist railway
  • site specific investigation and remediation of an active landslide

Key aspects under discussion will include;

  • the importance of thematic-based data models and authority tables
  • using symbology compatible with local standards (e.g. AS1726:2017 Geotechnical Site Investigations)
  • cartographic tools for detailed map presentation
  • accessing global data through web services
  • georeferencing plans and orthorectification of historic aerial photographs to understand site history
  • working with digital terrain models to understand and model landscapes
  • raster modelling using published (open-source) algorithms and bespoke python scripts to develop geotechnical models

About the Presenter Colin Mazengarb completed a MSc in geology from the University of Auckland and spent the following 20 years working as a regional geologist with the NZ Geological Survey and successor organisations. He migrated to Tasmania in 2003 to work as an engineering-geologist with the Tasmanian State Government, primarily undertaking landslide zoning. He was an early adopter of desktop GIS and the skills he has developed has been of great advantage throughout his career. Colin and his partner Janet have 3 children and one grandchild, all living in Hobart.