CHAPTER 12: OS MAPS AND AERIAL PHOTOS 12.3 Aerial photo skills
Photographs taken at different altitudes and angles can give us more up-to-date information than even the most recent of OS maps. Using maps and photos together helps us to build a better picture of an area. Aerial photographs are taken from an aeroplane or
helicopter. They show the present, but can also indicate features from the past that are invisible from the ground, e.g. ancient crop marks, overgrown/ demolished ancient settlements.
Aerial photos can be of two types: vertical and oblique. ~ A vertical photograph is taken when the camera points directly down over the subject matter of the photograph. The scale on this type of photo is the same across the image (i.e. true to scale). Use compass points to find the location.
~An oblique photograph is taken when the camera is pointing at an angle to the ground. It gives a side view of objects so they have depth, making them easier to identify. Oblique photographs can be low oblique (no horizon visible) or high oblique (horizon is visible). Use left, right, foreground, centreground and background notation to find location.
Fig. 36 Example of high oblique photo – Ballymun, Dublin
Fig. 37 Example of low oblique photo – Blanchardstown roundabout, Dublin