Integrating Airborne Laser Scanning with Data from Global Navigation Satellite Systems and Optical Sensors

Abstract

Most forestry applications of airborne laser scanning (ALS) require simultaneous use of various data sources. This chapter covers a number of common issues that practitioners face when dealing with data fusion schemes. The first subsection points out the objectives that may be pursued when integrating different data sources, and the benefits that can be obtained from using diverse remote sensors onboard differing platforms. The next subsections are devoted to the two data sources that usually pose most problems in their spatial co-registration with ALS datasets: field inventory and aerial photographs. All data sources ultimately rely on global navigation satellite systems (GNSS) which are especially error-prone when operating under forest canopies. Positioning methods and spatial accuracy assessment applied to forest plot and individual tree surveying are presented, also including terrestrial laser scanning (TLS). Furthermore, procedures for digital elevation model (DEM) generation are reviewed in the context of their use in orthorectification, which is the most widespread method for fusion of ALS with optical sensors. Drawbacks of using orthophotos are identified, therefore suggesting alternatives: true-orthorectification, back-projecting ALS and image matching.