Developing a spectral library for weed species in alpine vegetation communities to monitor their distribution using remote sensing

Authors: Kerrie Tomkins, Michael Chang – Department of Environmental Sciences, Macquarie University (Author for correspondence: and

Summary: This project examines the potential to use remote sensing for monitoring of the distribution of several weed species in the alpine region of NSW, specifically targeting Orange Hawkweed, Mouse-ear Hawkweed and Ox-eye Daisy, as requested by NPWS. The project is based on the premise that plants absorb and reflect different amounts of different wavelengths of light in the visible and near infrared spectra, which can be plotted as spectral reflectance profiles. We aimed to determine whether the spectral profiles of the weeds were separable from the spectral profiles of other common co-occurring native plants, and if so, determine whether it was possible to detect the weeds using spectral sensors attached to a drone, and/or using high-resolution satellite imagery.

The PSR+ Spectroradiometer was one of the instruments used during this study:

• Fast, full-spectrum UV-VIS-NIR measurements (350 – 2,500 nm)
• High Resolution Field Portable Spectroradiometer with 512 element Si array and two 256 element extended InGaAs arrays
• Various optics ranging from 1° to 25° for reflectance, radiance and irradiance measurements

Field-based operation:
• The PSR+ spectroradiometer is powered by batteries and connected to a rugged tablet which provides GPS, photo tagging, and voice notes
• Our self-developed software allows in-field mineral identification and classification
• Usage of handheld contact probe allows field measurements on outcrops or mapping open pits even at cloudy conditions

Laboratory operation:
• Best signal-to-noise ratio for improved reflectance values by using full range tungsten lamps
• Detailed analysis of field samples in order to build Arctic spectral libraries from natural covers

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