might need two, three, or four pictures to show the different sides of a building; or you might make a near and a distant view of the pinpoint target—one to show detail and the other to show location. You can also make more than one shot to produce one large, detailed picture of a pinpoint target. In this case, three or four shots  having  a  60-percent  overlap  are  made.  For example, you may need three overlapping exposures to give a large, detailed view of both ends and the middle of a bridge. When the number of overlapped exposures is small, say four or less, either vertical or oblique photographs,  the  total  composition  may  be  called  a pinpoint  aerial  photograph,  but  technically,  it  would  be either a strip or a mosaic. STRIP PHOTOGRAPHY A strip is a series of overlapping exposures matched together to form one long picture. A strip is used when your assignment calls for photographing long, narrow targets, such as railroads, highways, coastlines, rivers, and mountain ridges. You may hold the camera at any angle to make a strip; however, exposures made with the  camera  pointing  straight  down  from  the  aircraft  join together better and have the most consistent scale. A strip   comprised   of   oblique   views   is   called   a PANORAMIC. One  long,  continuous  picture,  made  from  a  number of photographs, requires the images to be matched carefully so one picture ends where the next begins. Because the camera is in a different position for each exposure,  a  perfect  match  is  impossible.  But,  by overlapping exposures and using only the central area of each picture, you can obtain a near-perfect result. Once  a  strip  is  started,  photographing  it  is  a mechanical job because the aircraft flies at a constant speed and at a constant altitude. You should not alter the camera angle while exposing a strip, and you should make the exposures at regular intervals. Thus the longer the strip, the more an automatic camera system is  preferred.  The  camera-to-scene  distance  must  remain constant while you are making the strip. The smallest change in distance changes the image size and makes matching adjacent exposures extremely difficult, if not impossible. MOSAIC PHOTOGRAPHY Large land areas are photographed in strips that overlap sideways. The strips are pieced together to form one large composite picture, called a MOSAIC. When photographing for mosaic purposes, you should keep the camera the same distance from the scene throughout the photographing evolution. Mosaics are usually produced from vertical photographs made by aircraft with an automatic camera system. STEREO  PHOTOGRAPHY Two pictures of the same subject, photographed properly,   can   provide   a   stereoscopic   or   three- dimensional effect. The two pictures are called a STEREO, a STEREOPAIR, or a STEREOGRAM. The word  STEREOGRAM  indicates that the two pictures are mounted and ready for stereo viewing. The primary purpose of stereo aerial photography is to provide measurements, such as height and depth, and detect features that are not visible in a regular photograph.   Photo   interpreters   (Intelligence Specialists) are trained in stereo techniques to detect these fine points. Stereo photographs are produced by making two pictures of the same subject from slightly different positions. When the pictures are made from the same position, the two are identical and there is not a  stereo  effect.  A  very  small  shift  in  the  camera position, between exposures, produces a very shallow stereoscopic depth. As you increase the shift in camera position between exposures, the apparent depth of the stereoscopic view increases. When the stereo effect is exaggerated—so  hills  appear  steeper  and  depressions appear deeper than they really are—the effect is called HYPERSTEREOSCOPY.  The  terms  inverted  stereo, pseudo stereo, and reverse stereo refer to the effect of interchanging  the  position  of  the  pictures,  causing  hills to appear as valleys and valleys to appear as hills. RECONNAISSANCE  PHOTOGRAPHY Another aspect of aerial photography that you should   be   concerned   with   is   reconnaissance photography.   The   Navy   performs   aerial reconnaissance photography of enemy territory to observe enemy defenses, troop concentrations, troop movements,  enemy  strength,  and  so  on.  Aerial reconnaissance  photography  may  also  include  taking images over friendly territory, both ours and our Allies. This is discussed further in the TARPS section of this chapter. CARTOGRAPHIC PHOTOGRAPHY Cartographic photography is accomplished for the purpose of making charts and maps. Usually several strips are flown over known landmarks that are used as reference   points   or   ground-control   points. Cartographic photography always has vertical views 4-6