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Abstract<br />

This study sets out an algorithm for the automatic analysis of controlled (flattened)<br />

aerial photography using ordnance survey vector data. It uses the vector to clip the<br />

aerial image into a set of small area polygons which are then analyzed for the<br />

spectral properties and classified according to the result. The study tests sections<br />

of aerial photography from a sample area in County Galway for specific spectral<br />

properties. This was to identify the type of ground cover and was achieved using<br />

an image key of spectral properties which was developed during the study. This is<br />

called training the image key. A testing section shows that it is possible to derive<br />

information about the land use type from these areas based on the range of values<br />

returned from a pixel count of spectral properties within a small area polygon.<br />

The study uses several open source software frameworks to complete the<br />

experiment, most notably the MATLAB based Mirone application, but can be<br />

extended to any software capable of handling irregular polygons in a projection<br />

system. The body of the study is set out in three chapters, the first detailing the<br />

process, the second detailing the sampling for unique values and the third details<br />

the testing which took place. Chapters 3 and 4 are sub divided into sections<br />

describing the research on specific land use types and their spectral signatures.<br />

Chopping an aerial image into a mosaic of (relatively) homogenous values, e.g.<br />

pasture, forestry, marsh etc., increases the accuracy of automated analysis. This is<br />

the first time that a spectral analysis has been attempted using ordnance survey<br />

Ireland small area polygons to clip the image. It is of interest to researchers,<br />

planners, developers etc., looking to simplify and automate this type of search<br />

over a large region.<br />

Note: Contact brian.sexton@osi.ie for a set of sample files for training the image<br />

key.<br />

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