The principle use of the video data is for geographic gridding of images and identification 

 of cloud-free areas. The coastal oceanographic use of video products is discussed in de- 

 tail in section III of this report. Only the VHR (1/3 n.mi. resolution video) was used in 

 this study, and it is available only for daytime, ascending node passes. During nightime 

 passes, the high sensitivity HR video data can be used for accurate gridding in clear sky 

 conditions, as city lights show up on the dark side of the earth. 



The problems and process of gridding the data are described in the USAF DAPP Users 

 Manual. The film product is essentially a strip chart with the image of the curved earth 

 surface projected on a plane film surface. The display equipment rectifies the data (re- 

 ducing the cylindrical distortion of foreshortening at the edges) and compensates for devia- 

 tions of the spacecraft from normal attitude and altitude. Manual gridding according to 

 instruction in the users manual, can locate land or oceanic features to within about 3 n.mi. 

 along track and about 1 .5 n.mi . across track near the data subpoint. Near the edge of 

 the data the error may increase to as much as 13 n.mi. along track and 8 n.mi. across 

 track due to spacecraft yaw errors that cannot be compensated for in the display. The 

 accuracy can be improved by adjusting the grid using geographical references and clear 

 sky VHR data. However, when there is a yaw error the grid will be accurate at the geo- 

 graphic reference points, and error will Increase away from those points. 



In the following section procedures for coastal oceanographic use of the DAPP system 

 will be specified with examples of the products. Normal meteorological display modes do 

 not reveal the oceanographic information content of the DAPP system data. 



III. PROCEDURES FOR COASTAL OCEANOGRAPHIC USE 



Display of Video Data (VHR) 



The optimum display mode of the visual range data for oceanographic use is low-level 

 enhancement and expansion of the image. Enhancement of low-level reflections brings 

 out the maximum detail in the oceanic and terrestrial regions free of clouds. Expansion of 

 the film products to a scale of 1:7,500,000 versus the normal 1:15,000,000 provides 

 fullest use of resolution capabilities and the most accurate manual gridding. In this way the 

 best presentations of Intricate coastline features In video and complex ocean thermal 

 patterns in Infrared data are obtained. The uses of the video image are as follows: 



• determination of cloud free areas for the most reliable HRIR sea surface temperature 

 data, 



• detection of patterns of reflected light from the oceanic areas, 



• location of land mass features of the region for manual gridding and geographic 

 reference, 



• location of satellite subpoint track with respect to the area of Interest. 



The patterns of reflected light from oceanic regions have not been subject to field 

 checks or positively Identified. Changes In video gain along the track during a pass, 

 significantly alter the amount of visual range reflection apparent from the sea surface. 



