Appendix 14. Remote Sensing

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1. Introduction

Remote sensing is the process of collecting data from a long distance using sensors and cameras mounted to aircraft and satellites. The spatial scale of the data makes it a powerful tool for catchment, national and global-scale assessments. Recent advances in the resolution of remotely sensed data has made it valuable in smaller scale assessments as well. Aerial photography such as Google Earth and Bing Maps are well-known examples of remotely sensed data.

2. Aerial Photography and Satellite Imagery

Both aerial photographs and satellite images are useful tools to look at original land features such as paleo-channels. Viewing a catchment from above also gives an idea of the drainage network and shows important features such as landuse and the extent of urbanisation within the catchment. It can also be used to show the development of a river following a signifcant event such as a restoration project.

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3. LiDAR

LiDAR (Light Detection And Ranging) is an optical remote sensing technology that measures properties of scattered light to find range and/or other information of a distant target. The prevalent method to determine distance to an object or surface is to use laser pulses. Like the similar radar technology, which uses radio waves, the distance to an object is determined by measuring the time delay between transmission of a pulse and detection of the reflected signal. LiDAR therefore gives you an idea of the height of the ground surface above a given datum. This can then be plotted (see Figure A12.1) and can show old meander channel and other palaeo-features.

Figure A12.1 : Example of LiDAR Data

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