Multispectral Remote Sensing from Unmanned Aircraft: Image Processing Workflows and Applications for Rangeland Environments

Abstract

Using unmanned aircraft systems (UAS) as remote sensing platforms offers the unique ability for repeated deployment for acquisition of high temporal resolution data at very high spatial resolution. Multispectral remote sensing applications from UAS are reported in the literature less commonly than applications using visible bands, although light-weight multispectral sensors for UAS are being used increasingly. . In this paper, we describe challenges and solutions associated with efficient processing of multispectral imagery to obtain orthorectified, radiometrically calibrated image mosaics for the purpose of rangeland vegetation classification. We developed automated batch processing methods for file conversion, band-to-band registration, radiometric correction, and orthorectification. An object-based image analysis approach was used to derive a species-level vegetation classification for the image mosaic with an overall accuracy of 87%. We obtained good correlations between: (1) ground and airborne spectral reflectance (R 2 = 0.92); and (2) spectral reflectance derived from airborne and WorldView-2 satellite data for selected vegetation and soil targets. UAS-acquired multispectral imagery provides quality high resolution information for rangeland applications with the potential for upscaling the data to larger areas using high resolution satellite imagery.

On the Use of Unmanned Aerial Systems for Environmental Monitoring

“…For instance, lightweight hyperspectral sensors for UAS are now available from different vendors (e.g., SPECIM; HYSPEX; HeadWall; see Appendix A), offering more defined and discrete spectral responses compared to the modified RGB or multiband cameras. Multispectral cameras commonly employ multiple lenses, which introduce band-to-band offsets that need to be adequately corrected in order to avoid artefacts introduced into the combined multiband product [48,49]. Both multispectral and hyperspectral cameras require radiometric calibration and atmospheric corrections to convert the recorded digital numbers (DN) to surface reflectance values to enable reliable assessment of ground features, comparison of repeated measurements, and reliable determination of spectral indices [50].…”

Low Power Greenhouse Gas Sensors for Unmanned Aerial Vehicles

“…Several UAV platforms have been used in environmental applications primarily focused on geographic surveying and high-resolution temporal and spatial imaging to complement LIDAR and satellite measurements [4,5]. However, there remains a significant technology gap in the development of high-performance, high-sensitivity trace gas sensors for the more common, less expensive, and smaller UAVs that have payloads on the order of 1 kg.…”

Photogrammetric mapping using unmanned aerial vehicle

“…The obtained results showed that UAV technologies have great potential to acquire such products. Other studies of a less common use of UAVs on remote sensing are presented by Laliberte et al, 2011, Turner et al, 2012and Khan et al, 2012 This paper shows a study of an UAV system used to acquire aerial images to generate orthoimages of a rural area, containing a small town. The main phases of work were subdivided into Photogrammetric flight mission, control and check points surveying, aerial triangulation, Digital Terrain Model (DTM) and orthoimage generation.…”