Bathymetry of Cannikin Lake, Amchitka Island, Alaska, with

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Stage-area-volume relacionships were calculared from the baafc dara. and the water-surface areas for different lake levels were measured using standard planimetric techniques. The manually-drawn map as well as the computer versions were ueed to obtain these relationehips. The two net6 of results are similar; they are shown on figure 3. COMPUTER-MAPPING TECHNIQUES The traverse dara obtained from the bothymetric survey of Cannikin take gave the authors an opportunity to rest the applicabitity of current computer-mapping techniqueu for traverse-type data. Bathymetric maps were produced using two different computer program (WET and Calcomp EPCP) and were compared with a manually-drawn bathymctric map. In addition to the bathjrmetric mpe, part of the WET computer program was used to produce an oblique three-dimeneional projection of the lake bruin, and to calculate the volume of water in the lake at given water lsvsls. There are three distinct uteps in computerized map production: 1. Data Preparation. Entablish an x-y coordinate system whose orientation and acale are compatible with the size and shape of the lake. The x and y coordinate of the data point and the measured -ake-bottom elevation at that point are coded and then key-punched on computer cards. 2. Data Conversion. The data from step L are used as input into a computer program which calculstea lab-bottw altitudes for an array of regularly-spaced points covering the entire area of the lake. 3. Manipulation of Converted Data. This array of x-y coordinates and calculated lake-bottom altitudes is used as input to one ir both of the computer programs. Each of the computer progrme is used to produce planimetric maps of the lake-bottom altitude*. Appropriate parts of the 9
WET computer program ate selecced ro produce oblique three-dirnens;loea1 projections, and to calculate the volume of water in rhe lake at given water levels. The parameters used in 8teps 2 and 3 that influence the quality of contour and oblique projection8 and volumetric calculations are grid size, map scale, contour interval, and tho x, y, and z coordi~tes of obsewarion points used in the production of oblique projections. The values of theee parameter8 are baaed on the type of basic data being inve&t:gated (clustered, sparse, Linear, etc.), the change in the calculared lake-bottom altitude values, specific control required, and directions and areas of interest. The WET Nahl-Evenden-Van Trump) program was written and (or) modified by R. R. Uahl, G. I. Evenden. and George Van Trump, Jr. of the U.S. Geological Survey. The program is designed to calculate surface values at grid intersections of a regularly-.paced grid using surface value. at irregularly- apaced pointo as input. The interpretative portion of this program emplaya a locally-weighted, leaat-square. surface-fitting technique. This program is designed to allow the user the option of using the output tape to produce a bathmetric mpp (fig. 4) or an oblique projection of the surface. The part of the program used to obtain the oblique projections is based on work by Wright (1973) and wan modified for use on the IBM 360-65. The Calcomp GPCP (Calcomp, 1971) program is available ior users of the U.S. Geological Survey IBM 360-65 computer system. This progranl also celculates surface values at grid intersections of a regularly-apaced grid using surface values at irregularly-.paced points &e input. The fnterpreta- tive part differ. from the WET program and consists of two operations. The
Page 2 and 3: . . , . . - . . ted Copj
Page 4 and 5: CONTENTS Page Abstract. . . . . . .
Page 6 and 7: This figure is not available in ele
Page 8 and 9: UNITIDJ STATES Amchitka-41 DEPARTME
Page 10: cavity-radii from the point of the
Page 13 and 14: The average annual precipitation is
Page 15: .> BATHYMETRY The bathymetric map o
Page 19 and 20: .... firer operation determinee the
Page 21 and 22: The middle part of the lake also la
Page 23 and 24: OBLIQUE PROJECTIONS The result of u
Page 25 and 26: Figure 6-- Oblique projection, Conn
Page 27 and 28: REFERENCES CITED Calcomp, 1971, A g
Page 29 and 30: Loa 4lamos Scientific Laboratory, L
Page 31: .- * U.S. Army Corpe of En~ineers,

Bathymetry of Cannikin Lake, Amchitka Island, Alaska, with

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