Quality Control of Lidar Data, Version 1.0.

Abstract

An important driver for the Regional Coastal Monitoring Programmes is that all data collected and made freely available should be quality-controlled in a thorough and consistent manner, to ensure that the data meets the Specification, with the result that the data can be used subsequently with confidence for a wide variety of coastal engineering and management tasks. This document describes the procedures used by the National Network of Regional Coastal Monitoring Programmes to quality-control lidar data, and can be used at three different levels: - A summary of QC tests, for those users who just want a brief overview of the generic quality control - Details of the quality control process including: o Workflow process i.e. the checks to be made and the most suitable order in which they are carried out. This section includes mandatory checks plus some optional checks depending on the landscape captured e.g. high cliffs, or on the deliverables in the Brief. o The methods used to carry out the checks, including the thresholds used. This section includes clear examples of what is and what is not acceptable. - Sample procedures for undertaking the checks. Those undertaking quality control may use any software or methods they wish, providing the QC standards are met. However, since most of the data quality control tests are expected to be done in a GIS, an example of a suitable procedure using ArcGIS (Standard licence, Spatial Analyst and 3D Analyst extensions) is given (Appendix B). The methods given here should also work in other GIS software1. Appendix A is a diagram summarising the quality control workflow Appendix B provides a procedure for ArcMap which can be used to complete the QC checks Appendix C provides a sample template to record the QC process Summary of QC tests The quality control tests fall broadly into two categories: - Data quality o Reached required depth at seaward limit o Water removal o Gaps o No striping/pocking o Removal of spikes e.g. flocks of birds, pylon cables o Polygon coverage o Structures included in DSM, excluded in DTM o Vertical accuracy o Flight lines (optional) o Point density (optional) o Profiles (optional) o Point density (optional) o Profiles (optional)