A method of identifying and analysing an aircraft landing site during flight, the method including the steps of using image capture means to capture in-flight images of the ground in the region of a possible landing site, using a database of computer modelled images of possible aircraft landing sites mapped to a global co-ordinate reference frame to compare the in-flight images with a modelled image of the possible landing site and optimising correspondence therebetween to obtain an in-flight image optimally mapped to the global co-ordinate reference frame, and analysing a landing site corresponding to the optimally mapped in-flight image to ascertain the presence of any life-forms thereon, characterised in that the analysis of the landing site for life-forms includes the steps of: analysing the in-flight image to detect the presence of an obstruction; analysing the portion of the in-flight image corresponding to the obstruction to detect the surface area of the obstruction by calculating the convex hull for the obstruction to define multiple polygons in the image domain and back projecting each polygon from the local image coordinate frame to the global world coordinate frame whereby to calculate the actual area of the obstruction and detect area above a threshold value; and determining the presence of life-forms based on the intensity and surface area of the obstruction, wherein determining the presence of life-forms comprises: generating a first statistical distribution of life-form thermal radiances having a mean and variance, and generating a second statistical distribution of life-form surface areas having a mean and variance; and generating a binary mask for the in-flight image by using the statistical distributions to calculate lower and upper thresholds of life-form surface area and thermal radiances, whereby obstructions having a detected surface area between the upper and lower thresholds of the life-form surface area and containing pixels having detected intensity values between the lower and upper thresholds of life-form thermal radiance are identified as being life-forms. analysing the in-flight image to detect the presence of an obstruction; analysing the portion of the in-flight image corresponding to the obstruction to detect the surface area of the obstruction by calculating the convex hull for the obstruction to define multiple polygons in the image domain and back projecting each polygon from the local image coordinate frame to the global world coordinate frame whereby to calculate the actual area of the obstruction and detect area above a threshold value; and determining the presence of life-forms based on the intensity and surface area of the obstruction, wherein determining the presence of life-forms comprises: generating a first statistical distribution of life-form thermal radiances having a mean and variance, and generating a second statistical distribution of life-form surface areas having a mean and variance; and generating a binary mask for the in-flight image by using the statistical distributions to calculate lower and upper thresholds of life-form surface area and thermal radiances, whereby obstructions having a detected surface area between the upper and lower thresholds of the life-form surface area and containing pixels having detected intensity values between the lower and upper thresholds of life-form thermal radiance are identified as being life-forms. generating a first statistical distribution of life-form thermal radiances having a mean and variance, and generating a second statistical distribution of life-form surface areas having a mean and variance; and generating a binary mask for the in-flight image by using the statistical distributions to calculate lower and upper thresholds of life-form surface area and thermal radiances, whereby obstructions having a detected surface area between the upper and lower thresholds of the life-form surface area and containing pixels having detected intensity values between the lower and upper thresholds of life-form thermal radiance are identified as being life-forms.