Abstract
Infrared (IR) Aerial Photographs of the Blue Mountains area, acquired with a Kodak multi-lens frame camera, are used to map vegetation communities. The present study is part of the project undertaken by the Blue Mountains City Council to map different types of vegetation accurately using both the conventional and Remote Sensing methods. Classifying the IR photos without any enhancement provides a poor result. An advanced technique using Decorrelation Stretched IR photos, Principal components and band ratios resulted with a much better classified image. The technique is presented in this paper. Subsequent study will evaluate the accuracy of this technique.

Keywords Infrared (IR) Aerial Photographs, Decorrelation Stretch, Principal Component Analysis, Band Ratio, Unsupervised Classification, Vignetting.

1 Introduction
The Blue Mountains is renowned for its unique environmental character. The natural ecosystems of the Blue Mountains that make up this character are recognized for therir outstanding ecological, scientific, recreational and heritage values and are deserving of nomination for world Heritage listing.

The different types of vegetation, (Rain Forest, Tall Open-Forest, Open-Forest, Montane Heath, Cekline Vegetation Escarpment and Rock Outcrop Vegetation, Swamps, Woodland/Low Woodland) that occur throughout the Blue Mountains area are the result of millions of year of evolution. Individual plant species have adapted to cope with the suite of environmental and physical factors that influence species habitats, including local geology, topography, climate and fire regimes. Vegetation communities in the Mountains are the combination of a range of plant species associated with a particular habitat. They are usually characterized by species composition and vegetation structure, and also represent fauna habitats thus providing a means of describing fauna distribution patterns as well as plant patterns.

The Blue Mountains City Council realizes the importance to preserve the native plants and to maintain the natural habitats of the native animals and hence is undertaking a vegetation mapping project. As part of the vegetation communities mapping project of the Blue Mountains City Council, the authors used Infrared Aerial photographs taken by Kodak multi-lens frame camera to map vegetation. Infrared Aerial photographs are used so as to take the advantage of the high Near Infrared reflectance of vegetation and high resolution of the Aerial Photographs (~14 cms resolution) in mapping vegetation.

1.1 Objective of the project
The main objective of the present study is to develop an algorithm that accurately map vegetation communities of the Blue Mountains area and subsequently to produce an accurate vegetation map of the area.

II Previous Studies
The standard methodology for conservation-related vegetation studies involves a process of compiling a plant species and vegetation community inventory for the survey area, mapping of the vegetation communities, and identification of the species and communities of special conservation significance (Smith & Smith 1998). There have been a number of vegetation mapping exercises that have classified vegetation communities in the Blue Mountains including Smith and Smith (1990), smith and smith (1995a-e) and Smith & smith (1998). These have provided valuable vegetation distribution data useful for regional planning purpose and to some extent, for local identification of significant vegetation.

The Smith and Smith (1995a-e) mapped vegetation from aerial photograph interpretation and field checked at a number of sites. The native vegetation types that wee recognized in the study were based on previous studies. The mapping covered urban areas of the Blue Mountains and adjacent lands up to 500m from the study area boundaries. Most parts of the study area were mapped from Qascophoto Cumberland 1:15000 colour photographs taken in April 1992. The northern third of North Katoomba was mapped from CMA 1:13000 colour photographs taken in May 1987.

There are concerns that relate to issues of the possibility that significant flora and fauna habitats have been inaccurately mapped, and the adequacy of protection for other areas of conservation significance which are not identified as significant in previous studies. Hence, the Blue Mountains city Council is undertaking further mapping of the extent of significant flora and fauna habitats in various areas to investigate claims that significant flora and fauna habitats that potentially cover a large number of land parcels have been grossly underestimated.