GIS & Remote Sensing

There are several methods through which height/elevation can be measured using satellite image and aerial photographs . In case of satellite image such as, Cartosat,  ASTER, Worldview I & II and others are used to create height or elevation data in the form of digital elevation model .  Aerial photography, LiDAR mapping are very common for creation of elevation data on higher scale/resolution for detailed study.  In the last article, relief displacement used to measure height of any object on earth surface. Here in this another method will be discussed to measure height of any given object on the earth surface. Parallax for Height Measurement using Aerial Photography Parallax Concept Photogrammetry is capable of measuring elevation of earth surface. Aerial photographs/stereo pair satellite images can be used to measure elevation differences through the use of parallax method.   New launched satellite are providing stereo pair satellite images images such worldview-2 etc.

Satellite image and aerial photographs are very important for mapping and creation of spatial data . As well as these aerial photographs and satellite images can be used to create elevation data.  Different methods employed for height measurement for a single given spot/location and also creation of digital elevation model . Therefore, in this article discuss about displacement in aerial photograph occurred due to relief or height of object on ground. Relief/Height/Elevation is the most significant source of image displacement. When point/object on the photograph is displaced from its datum position because of its elevation, a displacement take place so this displacement is called Relief displacement or displacement due to height of object. This relief displacement process can also help to calculate the height of object. This relief displacement is explained by below figure. In this Figure, ‘O’ is the camera station.  ‘NA' is a flat plain on which stands a tower ‘AB’

Aerial Photographs These photographs captured through balloon, aircraft and in current drones are used very commonly. These photographs represents aerial view of land use and land cover .   Aerial photographs categorized in vertical, low oblique and high oblique depend upon angle from nadir and area covered in aerial photographs.   These photographs are very useful for mapping and monitoring due its high spatial resolution. Such detail information captured through aerial photographs can be used to create spatial data and further analysis in GIS and Remote Sensing . Spatial resolution of satellite images can be represented in the form of scale. This scale defined the quality of information, which can be called information in detail. More details information its mean good spatial resolution. Scale of Aerial Photographs Scale is the relationship between distance on a map or photo and the actual ground distance.   Scale is one of the important parameter for aerial photographs/ Sat