APPENDIX D 



PHYSICAL PROPERTIES OF ICEBERGS 

 TOTAL MASS DETERMINATION 



R. Quincy Robe 



and 

 L. Dennis Farmer 



U.S. Coast Guard Research and Development Center 



Analysis of stereo pairs of twenty-two icebergs, 

 in the region of Davis Straits, reveals that a 

 reasonable estimate, of total iceberg mass, in 

 metric tons, can be arrived at by multiplying the 

 gross dimensions of the iceberg (height x width 

 x length) together and the multiplying this 

 product by a factor of 3.01. This factor accounts 

 for the density difference between seawater and 

 fresh water ice; it also accounts for the average 

 shape and mass distribution of icebergs. 



Introduction 



Before a model for the deterioration of icebergs 

 can be constructed and verified, it is necessary 

 that actual observations be made of icebergs 

 melting and calving. A prerequisite for deteriora- 

 tion observations is a simple technique for the 

 determination of iceberg mass. KOLLMEYER 

 (1966) determined the mass of icebergs by con- 

 structing a contour map of the berg using hori- 

 zontal photographs taken at intervals of every 

 30° of arc around the berg. This technique was 

 very laborious, not very accurate, and could not 

 be used to cover many bergs. We felt that a 

 more practical approach was to use aerial pho- 

 tography and construct a topographic type map 

 of the bergs from stereo pairs. Since we lacked 

 any vertical control points, such as exist on land, 

 horizontal and oblique photographs were taken 

 to provide a measure of vertical scale. 



In order to obtain the necessary photography 

 the CGC EDISTO was used for a platform for 

 two HH52 helicopters. The EDISTO was as- 

 signed to this project from approximately 16 



July 1974 until 4 August 1974. The first icebergs 

 photographed were just north of Goosebay, 

 Labrador. From there the EDISTO proceeded 

 north, until just north of the Arctic Circle, work- 

 ing icebergs as we went. From the Davis Straits 

 area just north of the Arctic Circle we proceed 

 south and then east in order to pick up icebergs 

 off the west coast of Greenland. 



Data Collection 



Thirty-two icebergs were photographed. Of 

 these, twenty-one were of high enough quality to 

 determine the above water volume. Hydro- 

 graphic stations taken near each iceberg measured 

 the average density of the seawater in the area. 



Aerial photography was acquired from USCG 

 HH52 helicopters, using 500 EL Hasselblad 70 

 mm format cameras with 100 mm f3.5 lenses. 

 These cameras were installed in a lightweight 

 aerodynamic camera mount designed at the CG 

 R&D Center. The mount is a lightweight (85 

 pounds with four cameras) multi-purpose unit 

 which requires no airframe modification for in- 

 stallation. Design limits are air speeds 140 knots 

 or less and unpressurized flight altitudes. The 

 practical limiting altitude is 6,000 feet. The 

 mount is designed to fit all Coast Guard aircraft 

 capable of meeting these limits. 



Parallax measurements used in determining 

 heights of points on the iceberg were made on 

 stereographic photographs with the model 121 

 GE stereo comparagraph. Sea level cross- 

 sectional area was measured with the B&L photo 

 data quantitizer. 



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