Book Image

QGIS By Example

By : Alexander Bruy, Daria Svidzinska
Book Image

QGIS By Example

By: Alexander Bruy, Daria Svidzinska

Overview of this book

Table of Contents (17 chapters)
QGIS By Example
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

The basics of visibility analysis


The aim of visibility analysis is to produce a coverage of an area that can be seen from a specified location. This coverage is called a viewshed, which is why the terms visibility analysis and viewshed analysis are used interchangeably. To perform a simple visibility analysis, you need to define at least two components:

  • Observation point: A point that represents an observer's position and for which visibility is being analyzed

  • DEM: This represents irregularities in the earth's surface and is used to examine visibility along the line of sight

The idea underlying the process of this analysis is to compare the height of the observation point against the height of earth's surface point along the given line of sight. If the height of the surface point is less than that of the observation point, then it will be seen from the current position; if it is higher, the visibility line will be blocked. Similarly, all points within a certain radius are compared against...