Spatial Analysis of Oblique Photo-point Images for Quantifying Spatio-temporal Changes in Plant Communities

Applied Vegetation Science, Volume 13, Issue 2, pages 173–182, April 2010

P. Michel, R. Mathieu, and A.F. Mark

Question: Can spatial analytical techniques be used to extract quantitative measurements of vegetation communities from ground-based permanent photo-point images?

Location: Mount Aspiring National Park, south-western South Island, New Zealand.

Methods: Sets of ground-based photographs representing two contrasting vegetation types were selected to test two spatial analytical techniques. In the grid technique, a grid was superimposed onto the photographs and the frequency of species presence in each grid-square was calculated to estimate species abundance/cover over the defined area. In the object-oriented technique, the photographs were segmented into meaningful objects, based on the colour of the pixels and the textural patterns of the images, and the area occupied by an object in the image was used to derive species abundance/cover over the area.

Results: Both techniques allow quick and easy classification of digital elements into ecologically relevant categories of vegetation components. The grid technique appeared more robust, being quick and efficient, accommodating all image types and providing presence/absence matrices for multivariate analysis. Fewer classes were identified using the object-oriented technique, in particular for the forest interior site and for small individual plants such as Astelia spp.

Conclusions: Both techniques showed potential for the objective quantitative analysis of long-term vegetation monitoring of cover and changes of several component species, using repeat ground-based photographs more specifically for grassland habitats. However, both rely to various degrees on manual classification. Corrective factors and strict protocols for taking the photographs are necessary to account for variation in view angles and to compute values more representative of absolute species abundance.”

Spatial Analysis of the 2008 Influenza Outbreak of Hong Kong

Lecture Notes in Computer Science, 2010, Volume 6016/2010, 374-388

Poh-chin Lai and Kim-hung Kwong

“The deaths of three children amid a series of recent influenza outbreaks in early March 2008 resulted in the immediate shut down of all kindergartens and primary schools in Hong Kong. While many parents welcome the decision, others queried the judgment given that citizens lack sufficient information to evaluate whether there is an outbreak and must follow actions prescribed by the government. We demonstrated in this paper various techniques to visualize disease distribution and present outbreak data for public consumption. Our analyses made use of affected (case) and non-affected (control) schools with influenza cases in March 2008. A series of maps were created to show disease spread and concentration by means of standard deviational ellipses, grid-based spatial autocorrelation, and kernel density. The generalized data did not permit statistical analysis other than the nearest neighbor distance. We also made suggestions about requirements of additional data and possible directions of disease analysis. ”