The Stereo Pair 3D Measurement process allows you to select a common point from two stereo images and calculate an elevation value for that point.There are three steps in creating a DEM that are crucial to generating acceptable results: epipolar image creation, image matching, and DEM geocoding.
Epipolar Image Creation - The creation of epipolar images is an essential processing step in DEM extraction. Epipolar geometry describes the geometrical constraint between two frame images of a stereo pair. It represents the fact that a ground point and the two optical centers lie on the same plane. This means that for a given point in one image, its conjugate point in the other image must lie on a known line in the second image. By creating epipolar images, the search space for finding corresponding image points in automatic image matching is reduced. For information about building epipolar images for the use with DEM Extraction Wizard, see Building Epipolar Images.
Image Matching - Image matching finds the conjugate points on both the left and right images which correspond to the same ground feature. The output of the image matching procedure is called a parallax image, in which the x-coordinate difference (along epipolar lines) between the left and right image is stored and is used to build the DEM. Thus, the quality of image matching largely determines the quality of the output DEM.
DEM Geocoding - DEM geocoding re-projects the DEM from the epipolar projection to the user-specified output map projection and units. This step involves the filling of failed pixels and the resampling to a pixel spacing specified by the user. When GCPs are provided, the absolute orientation of the computed terrain model is performed in this step.
Volgograd Arena (45,000 spectators): An emotional World Cup venue. On the bank of the Volga, the new stadium was built against the backdrop of the war memorial "Mother's Homeland Calls". During construction, bones were found by soldiers of the Second World War.
Group matches: Tunisia - England (June 18); Nigeria - Iceland (22 June); Saudi Arabia - Egypt (25 June); Japan - Poland (June 28)
Mordovia Arena (45,000 spectators): On the outskirts of Saransk, the new building was launched in 2010, the 1000th anniversary of the unification of the Mordovian and Russian population. After the World Cup there will be a dismantling for tennis and volleyball fields.
Group matches: Peru - Denmark (16 June); Colombia - Japan (19 June); Iran - Portugal (25 June); Panama - Tunisia (June 28)
Samara Arena (45,000 spectators): The ambitious construction project in the forest just outside the city lagged behind the schedule for a long time.
Group matches: Costa Rica - Serbia (17 June); Denmark - Australia (21 June); Uruguay - Russia (25 June); Senegal - Colombia (June 28)
A knockout round, a quarter-finals | Source: REUTERS
Rostov on the Don-Arena (45,000 spectators): Right on the banks of the Don is the new arena. The roof of the new building should symbolize the course of the river. FK Rostov, who beat the Bavarians in the Champions League, is playing here after the World Cup.
Group matches: Brazil - Switzerland (17 June); Uruguay - Saudi Arabia (June 20); South Korea - Mexico (23 June); Iceland - Croatia (June 26th)
A knockout round | Source: REUTERS