reconnaissance and ice report 

 dissemination. Finally, the environmental 

 and logistical challenges estimating where 

 appropriate iceberg targets might be on a 

 particular day, extremely variable and 

 frequently inhospitable weather and sea 

 conditions, as well as airframe 

 serviceability and aircraft radar operation 

 imposed nearly insurmountable obstacles 

 in this study. We requested RADARSAT 

 scenes on 25 July 97 (SCN), 28 July 97 

 (W-2), 25 April 98 (W-2) and 28 April 98 

 (W-2). All scenes were affected by either 

 aircraft or weather logistics or by 

 unfavorable iceberg distribution, except for 

 one of the 28 July 97 W-2 images. This 

 image was obtained at approximately 

 09:44 UTC, descending pass, centered on 

 50°49'N 52°10'W, with a pixel spacing of 

 12.5 meters. 



Image Processing and Visual 

 Reconnaissance 



This image was processed using a 

 range equalization function and a speckle 

 suppression routine consisting of two 

 consecutive Lee-Sigma filters with 3x3 

 windows. These processing functions 

 were found in the ERDAS Imagine (a 

 commercially available image processing 

 program) v8.3 interface. Though not 

 cutting-edge techniques, these 

 corrections allowed us to easily 

 eliminate much of the speckle and 

 range variation found in the 

 image. Fortunately, the image 

 was completely over ocean and 

 contained no terrestrial 



illumination. The processing 

 produced an array of 16 bit pixels 

 yielding digital numbers (DN) in 

 the range to 65536. By 

 individual comparison of the point 

 targets in the scene, as indicated 

 by "bright splotches", we were 

 able to characterize targets as 

 grouped pixels collectively brighter 



than approximately 5500. The areas of 

 interest containing brightness values for 

 identified targets were extracted from 

 RADARSAT scenes as ASCII text arrays 

 and imported into Microsoft Excel 

 worksheets for graphing and manipulation. 

 As a secondary measure, the scene was 

 run through the Canadian Centre for 

 Remote Sensing's 



(CCRS) Ocean Monitoring Workstation 

 (OMW). Initial arguments used were: 

 minimum targets size of 3 pixels, target 

 separation of 500m, maximum target size 

 of 550m and a land mask of 1500m. Ten 

 certain targets resulted with target sizes 

 ranging from 64 pixels to 3 pixels (Table 1). 



A typical International Ice Patrol 

 reconnaissance flight track was flown over 

 the area of the 28 JUL 98 RADARSAT 

 scene, consisting of a "ladder search" with 

 150-nautical mile (275km), north-south 

 oriented legs and cross legs of 30 nautical 

 miles (55 km) (Figure 2). These flights are 

 usually flown at an altitude of 8000 ft (2.4 

 km) but for visual reconnaissance and 

 pictures, the icebergs were observed at 

 400 ft (730 m). The airplane, CG-1503, 

 departed St. John's Airport at 10:00 UTC 

 and the crew detected the final contact 

 within the footprint area at 13:23 UTC. The 

 weather conditions were excellent: 20 



58 



