University of Twente Student Theses


Assessing spatial structure of vegetation patches at multi-spatial resolutions and studying effect of scale for analyzing spatial variation

Sharma, Priyanka (2012) Assessing spatial structure of vegetation patches at multi-spatial resolutions and studying effect of scale for analyzing spatial variation.

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Abstract:With objective to explore potential of variogram analysis for analysing spatial structure of vegetation across scales, present study was an attempt to quantify spatial structure of vegetation patches at three different resolutions (LISS IV, LISS III and AWiFS) and to model it using variogram parameters (nugget, sill and range). Initially variogram analysis was carried out on subsets selected from different vegetation types(namely dense forest, open forest, agricultural land and mixed forest) taken from two study areas Dehradun & Haldwani (mainly Sal, Pine and Oak trees) to understand the spatial structure of these subsets at LISS IV resolution. It was found that variogram behaviour was almost similar for dense and open forest but variance was much higher for agricultural land and a patch present in urban areas. Four cases A, B, C and D were constructed to study the information associated with the patch boundary where Case A includes homogeneous vegetation patch, Case B includes non vegetation area present along the boundaries of a vegetation patch, Case C includes binary image having two classes i.e. vegetation (0) and non vegetation (1), and Case D includes the area after excluding a vegetation area (Case A). Variogram analysis across scales of homogeneous patches revealed the spatial structure of vegetation patches at different scales A change was observed in variogram parameters due to seasonal variation. Binary and non binary images have shown different variogram behaviour, smaller range in binary cases as compared to gray images represented in Case B. Also, the binary images had higher variance increasing exponentially as expected as binary cases represented indicator variogramps of presence/absence of vegetation patch. It was observed that homogeneity of a vegetation patch relates to variance and range of a variogram. Different variogram behaviours of simulated and original images reveal that seasonal and temporal factors associated with vegetation have a strong impact on variogram shape thus a change in spatial structure of the vegetation patches. The study helped us to quantify spatial structure of vegetation patches considered and thus provided help to decide appropriate resolution of study for a particular type of vegetation. As spatial structures also indicates texture signature, outcome of this study can further be explored for its potential for a higher level of vegetation classification. KEY WORDS Scale, Resolution, Vegetation Patches, Spatial Structure, Pattern, Shape, Boundary, NDVI, Variogram, Geostatistics, Transition Zones
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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