Mapping Pure Mangrove Patches in Small Corridors and Sandbanks Using Airborne Hyperspectral Imagery

Taijiang National Park (TNP) of Taiwan is the northernmost geographical position of mangrove habitats in the Northern Hemisphere. Instead of occupying a vast region with a single species, the mangroves in TNP are usually mingled with other plants in a narrow corridor along the water or in groups on a small sandbank. The multi-spectral images acquired from the spaceborne platforms are therefore limited in mapping the abundance and distribution of the mangrove species in TNP. We report the work of mapping pure mangrove patches in small corridors and sandbanks in TNP using airborne Compact Airborne Spectrographic Imager (CASI) hyperspectral imagery. Bu considering the similarity of spectral reflectance among three species of mangrove and other plants, we followed the concept of supervised classification to select a few training areas with known mangrove trees, where the training areas are determined from the detailed map of mangrove distribution derived from the field investigation. The Hourglass hyperspectral analysis technique was employed to identify the endmembers of pure mangrove in the training areas. The results are consistent with the current distribution of mangrove trees, and the remarkable feature of a “mangrove desert” highlights a fact that biodiversity can be easily and quickly destroyed if no protection is provided. Some remnant patches located by this research are very important to the management of mangrove trees.

Estimación de variables biofísicas del pastizal en un ecosistema de dehesa a partir de espectro-radiometría de campo e imágenes hiperespectrales aeroportadas

<p>The aim of this paper is the estimation of biophysical vegetation parameters from its optical properties. The variables Fuel Moisture Content (<em>FMC</em>), Canopy Water Content (<em>CWC</em>), Leaf Area Index (<em>LAI</em>), dry matter (Cm) and AboveGround Biomass (AGB) were estimated in the laboratory from vegetation samples collected simultaneously with the acquisition of spectral data from the Compact Airborne Spectrographic Imager (CASI) sensor and the field spectroradiometer ASD FieldSpec® 3. Spectral vegetation indices found in the literature were computed from hyperspectral data. Their linear relationships with the biophysical variables measured in the field were analysed. Results show consistent relationships between analysed biophysical parameters and spectral indices, mainly those using SWIR and red-egde bands which reveal the importance of these spectral regions for the estimation of biophysical variables in herbaceous covers. Determination coefficients (<em>R²</em>) above 0.91 and <em>RRMSE</em> of 21.4% have been obtained for the spectral indexes calculated whit ASD data, and 0.91 <em>R²</em>and <em>RRMSE</em> of 15.5% for the spectral indexes calculated whit CASI data.</p>

Análisis espectral del arrecife coralino de Cayos Arcas, Campeche, México

La utilización de sensores remotos aerotransportados con alta resolución espectral o hiperespectrales, ha venido incrementándose, paulatinamente, en estudios de elementos sobre la superficie terrestre. En particular, el estudio de cuerpos de agua mediante estos instrumentos ha recibido un gran impulso en los últimos años, en diversos campos de investigación. El objetivo de este trabajo es mostrar una caracterización espacial del arrecife coralino de Cayos Arcas utilizando el sensor hiperespectral aerotransportado CASI (Compact Airborne Spectrographic Imager). Los resultados obtenidos mediante el procesamiento de imágenes muestran que es posible la detección de sedimento (distribución y patrones de transporte), la batimetría y las características fisiográficas de la región entre los aspectos más importantes.