6 research outputs found
Mapping relict arctic-alpine tundra vegetation from multitemporal LiDAR data
Práce se zabĂ˝vá parametry vertikálnĂ struktury vegetace odvozenĂ˝mi z UAV LiDARovĂ˝ch dat a jejich vyuĹľitĂm k multitemporálnĂ klasifikaci vybranĂ˝ch druhĹŻ arkto-alpinskĂ© tundry Krkonoš. Na základÄ› rešerše literatury se zaměřenĂm na nĂzkĂ© a keĹ™ovitĂ© porosty jsou vytipovány strukturnĂ parametry. Jejich vhodnost k rozlišenĂ tundrovitĂ© vegetace je hodnocena algoritmem Random Forest a metodou urÄŤenĂ dĹŻleĹľitosti prediktorĹŻ pomocĂ permutace out-of bag pozorovánĂ, vynechánĂm prediktoru a individuálnĂ vĂ˝konnostĂ prediktoru. NáslednÄ› je provedena fĂşze s multispektrálnĂmi daty a urÄŤen vliv LiDAR odvozenĂ˝ch strukturnĂch parametrĹŻ na zpĹ™esnÄ›nĂ vĂ˝sledkĹŻ klasifikace. Zkoumány jsou takĂ© strukturnĂ parametry vegetace odvozenĂ© z digitálnĂho modelu povrchu zĂskanĂ©ho obrazovou korelacĂ multispektrálnĂch dat. Pro odlišenĂ vegetaÄŤnĂch tĹ™Ăd byl jako nejvhodnÄ›jšà urÄŤen parametr maximálnĂ výšky, následován minimálnĂ výškou, relativnĂm pomÄ›rem povrchu vegetace a koeficientem variace, kterĂ© dosáhly celkovĂ© klasifikaÄŤnĂ pĹ™esnosti 67,3 % pro BĂlou louku a 62,3 % pro ĂšpskĂ© rašeliništÄ›. FĂşze s multispektrálnĂmi daty vedla k zpĹ™esnÄ›nĂ klasifikace do 2 %. V pĹ™ĂpadÄ› struktury vegetace odvozenĂ© z digitálnĂho modelu povrchu bylo dosaĹľeno stejnĂ©ho vĂ˝sledku s vĂ˝jimkou vyššĂch porostĹŻ. LiDARová data se neukázala jako pĹ™Ănosná k odlišenĂ...The thesis focuses on metrics of vertical structure of vegetation derived from UAV LiDAR data and their use for multitemporal classification of selected species of arctic-alpine tundra in the Krkonoše Mountains. The metrics are selected based on a literature search focusing on low and shrubby stands. Random Forest algorithm and permutation feature importance, drop column importance and individual predictor performance is used to determine the suitability of metrics for distinguishing tundra vegetation. Subsequently, a fusion with multispectral data is performed and influence of the LiDAR derived variables on the refinement of classification results is determined. The use of metrics derived from a digital surface model obtained by image correlation of multispectral data is also examined. Maximum height followed by minimum height, canopy relief ratio and coefficient of variation yielded the best results, they achieved an overall classification accuracy of 67.3% for BĂlá louka meadow and 62.3% for ĂšpskĂ© rašeliništÄ› bog. Fusion with multispectral data led to an increase in overall accuracy up to 2 %. In case of vegetation structure derived from the digital surface model, similar results were achieved apart from higher stands. LiDAR data did not prove to be beneficial in distinguishing grass communities...Department of Applied Geoinformatics and CartographyKatedra aplikovanĂ© geoinformatiky a kartografieFaculty of SciencePĹ™ĂrodovÄ›decká fakult
The utility of new generation multispectral sensors in assessing aboveground biomass of Phragmites australis in wetlands areas in the City of Tshwane Metropolitan Municipality; South Africa.
Master of Science in Environmental Science. University of KwaZulu-Natal. Pietermaritzburg, 2017.Abstract available in PDF file
The impact of land use and land cover changes on wetland productivity and hydrological systems in the Limpopo transboundary river basin, South Africa
Philosophiae Doctor - PhDWetlands are highly productive systems that act as habitats for a variety of flora and fauna. Despite their ecohydrological significance, wetland ecosystems are under severe threat as a result of environmental changes (e.g. the changing temperature and rainfall), as well as pressure from anthropogenic land use activities (e.g. agriculture, rural-urban development and dam construction). Such changes result in severe disturbances in the hydrology, plant species composition, spatial distribution, productivity and diversity of wetlands, as well as their ability to offer critical ecosystem goods and services. However, wetland degradation varies considerably from place to place, with severe degradation occurring particularly in developing regions, such as sub-Saharan Africa, where Land Use and Land Cover changes impact on wetland ecosystems by affecting the diversity of plant species, productivity, as well as the wetland hydrology