orientation to the radar transmission, its contrast (to 

 the radar), etc. In addition, requirements vary greatly 

 from application to application. A 20 x 20 m, 4-looks 

 spatial resolution was established as optimal in that this 

 is probably the maximum resolution that can be expected of 

 satellite SAR systems by 1990. A spatial resolution of 25 

 X 25 m, 4 looks, identical to Seasat performance, is 

 acceptable; 30 x 50 m, 4 looks is marginal. 



5. Geometric Positioning 



Requirements for positioning or registration in latitude and 

 longitude stated by applications teams are summarized as follows: 



a. Renewable Land Resources 



A value of 25 m was established by personal communication 

 with team members. All figures apply to position accuracy 

 in an image which has been geometrically corrected to 

 ground control points. 



b. Nonrenewable Land Resources 



The Nonrenewable Land Resources Team is concerned that 

 geometric positioning be sufficiently accurate to permit 

 coregistration with other digital data sets. Although 

 they recognize that in SAR imagery accuracies will vary 

 considerably as the distance from ground control points 

 increases, they feel that a considerable effort should be 

 made to achieve absolute accuracies of 40 m. Accuracies 

 of up to 150 m will still permit extraction of useful 

 imagery and are acceptable. 



c. Ice 



A great deal of the ice information will be acquired over 

 water or ice precluding the use of ground control points 

 to facilitate geometric correction. A figure of 100 m is 

 sufficiently accurate to meet most rapid turnaround 

 requirements. 



d. Oceans 



The Oceans Team has not discussed a need for specific 

 geometric position accuracy. It is assumed that the 100 m 

 suggested by the Ice Team will meet their requirement. 



5-13 



