On Monday, 11 July from 3:00 p.m. through Wednesday, 13 July until 5:00 p.m. (USA Mountain Time), NSIDC data distribution, services, and Web site will be unavailable to accommodate a major upgrade to our data center. We apologize for any inconvenience this may cause you. Need to talk to us? You can always contact our friendly User Services Office at firstname.lastname@example.org or + 1 303.492.6199.
Manned Station and Unmanned Buoy Drift Positions Coordinated Eastern Arctic Experiment (CEAREX) Miles G. McPhee McPhee Research Company 450 Clover Springs Road Naches, Washington 98937 USA 1. Description This data set contains a summary of CEAREX manned station and unmanned buoy drift positions. There are 24 ASCII data files, each with one header record followed by "position fix" records with (1) time in decimal days of the year; (2) latitude in decimal degrees; (3) longitude in decimal degrees (east positive); and, for the manned camps, (4) an integer source code described in sections 3.4, 3.5 and 3.6, below. The data were perused, and any obvious outliers were marked with asterisks. In addition, there are hourly listings of position and velocity for the manned camps (PBHOURLY.POS = Polarbjorn drift, OHOURLY.POS = O Camp, AHOURLY.POS = A Camp) from the complex demodulation algorithm as described in the reports distributed at the CEAREX Workshop and Publications Planning Meeting, 8-10 February 1990, Long Beach, Mississippi. (McPhee, M.G., 1988, Analysis and prediction of short term ice drift. Transactions of the ASME, Journal of Offshore Mechanics and Arctic Engineering, vol. 110, p. 94-100.) 2. Complex Demodulation Procedure. Briefly, the complex demodulation procedure moves a 24-hour window through the data at 6 hour intervals, calculating a least-squares fit of 6 complex coefficients, from which position and velocity are derived. If there are not enough fixes (12) in the window, or if there is a gap of more than 6 hours, the complex demodulation is replaced with a linear fit for position. In the hourly files, this causes a step structure in the velocity, since it is constant over the 6 hours. In order to keep the amount of data manageable, results of complex demodulation for the buoys are not included; however, the subdirectory "programs" contains both the required routines and a UNIX session for generating the file `AHOURLY.POS'. [Special Notes About Filenames: Filenames on this CD-ROM are in upper case because the directory structure is based on MS-DOS. Take this into account when transferring files to a Unix environment. See section 4 for an additional note about the programs.] 3. File Contents. 3.1. POLARBJORN Drift, O Camp Drift, A Camp Drift Data Files 3.1.1. Filenames and Headers Data files on this CD-ROM are numbered [4nnn.POS, 6nnn.POS, 7nnn.POS, 8441.POS] or named [PBDRIFT.POS, OCAMP.POS, ACAMP.POS, PBHOURLY.POS (POLARBJORN drift hourly), OHOURLY.POS (O Camp hourly), and AHOURLY.POS (A Camp hourly)]. MS-DOS conventions limit filenames to eight characters. Headers for these files contain information about the file contents: original filename, `0' (zero), year, start time (in decimal days of the year), end time (in decimal days of the year), number of fixes, and PI for data collection. 3.1.2. POLARBJORN Drift, James Morison, PI Filename: PBDRIFT.POS [hourly file: PBHOURLY.POS] Header: 65-character record providing information about the start and end times and the source of the data. This is not a traditional "field" header. pbdrift 0 1988 start 260.37153 end 335.1278 fixes 4776 PI bunch ERIM satnav fixes = code 0 PSC Salargos buoy = code 1 ERIM dead reckoning estimates = code 2 Scripps ADCP satnav fixes = code 3 Flag is `*' to indicate outlying data points. Data records are 65 characters. 3.1.3. O Camp Drift, Miles McPhee, PI Filename: OCAMP.POS [hourly file: OHOURLY.POS] Header: 62-character record providing information about the start and end times and the source of the data. This is not a traditional "field" header. ocamp 0 1989 start 78.4306 end 120.7347 fixes 753 PI McPhee PSC satnav fixes = code 0 PSC Salargos buoy = code 1 MFO log from satellite navigator = code 2 Flag is `*' to indicate outlying data points. Data records are 62 characters. 3.1.4. Alpha Camp Drift, Arthur Baggeroer, PI Filename: ACAMP.POS [hourly file: AHOURLY.POS] Header: 67-character record providing information about the start and end times and the source of the data. This is not a traditional "field" header. alpha 0 1989 start 82.27431 end 110.43775 fixes 680 PI Baggeroer MIT satnav fixes Code is not used because all fixes are from MIT satnav. Flag is `*' to indicate outlying data points. Data records are 67 characters. 3.2. Buoy Data Files 3.2.1. The headers shown below for each of the data files provide information about the file contents: type, filename, year, start date (in decimal days of the year), end date (in decimal days of the year), number of fixes, and PI for data collection. All the filenames beginning with numbers have the same format, although the record size varies. 3.2.2. Robin D. Muench and Arthur Baggeroer Filenames: 4886.POS ==> 4899.POS Header: ptt 4886 1989 start 96.09881 end 107.94616 fixes 67 PI Baggeroer/Muench ptt 4890 1989 start 90.99833 end 109.32020 fixes 207 PI Baggeroer/Muench ptt 4897 1989 start 91.03516 end 109.50545 fixes 361 PI Baggeroer/Muench ptt 4899 1989 start 90.96494 end 103.06101 fixes 232 PI Baggeroer/Muench Data and headers: 74-character records 3.2.3. Jean-Claude Gascard Filenames: 6110.POS ==> 6119.POS Header: ptt 6110 1989 start 91.56365 end 184.83350 fixes 2143 PI Gascard ptt 6111 1989 start 90.50036 end 200.79429 fixes 2421 PI Gascard ptt 6112 1989 start 93.49718 end 296.27713 fixes 1369 PI Gascard ptt 6113 1989 start 95.53391 end 214.66140 fixes 2559 PI Gascard ptt 6114 1989 start 94.68361 end 232.67072 fixes 2966 PI Gascard ptt 6115 1989 start 91.56296 end 198.14800 fixes 2386 PI Gascard ptt 6116 1989 start 88.71596 end 142.05626 fixes 1159 PI Gascard ptt 6117 1989 start 93.63753 end 267.06992 fixes 1875 PI Gascard ptt 6118 1989 start 88.65594 end 214.73418 fixes 2790 PI Gascard ptt 6119 1989 start 90.50072 end 186.94223 fixes 2276 PI Gascard Data and headers: 65-character records. 3.2.4. James Overland Filenames: 7100.POS ==> 7105.POS Header: ptt 7100 1988 start 260.68355 end 324.72720 fixes 1234 PI Overland ptt 7101 1988 start 261.58638 end 486.91866 fixes 4002 PI Overland ptt 7102 1988 start 260.75404 end 425.88196 fixes 3096 PI Overland ptt 7103 1988 start 261.51644 end 425.88208 fixes 3324 PI Overland ptt 7104 1988 start 261.38729 end 407.35451 fixes 2765 PI Overland ptt 7105 1988 start 261.65786 end 425.88211 fixes 3060 PI Overland Data and headers: 66-character records. 4. How to Use the Programs. The programs provided on this CD-ROM were written in the C programming language by M.G. McPhee, for use on a SUN workstation. They are written on the CD-ROM as received from the author, with some minor changes in filenames for MS-DOS compatibility. [See the following paragraph for information on the record size and padding.] Please note that the programs contain references to SUN Unix utilities and assume SUN Unix conventions. Special Notes on Using the Programs on this CD-ROM: The filenames on this CD-ROM all have 3-character extensions, a function of the software used to produce this CD-ROM. Because of this, the C programs in the directory \POSITION\POSPRG have extensions .CXX or .HXX rather than .C or .H as you would expect. You will need to copy the program files to your hard (or floppy) disk with the normal .C or .H extensions before attempting to use the programs. Also note the use of lower case within the programs and upper case in the DOS-compatible filenames on the CD-ROM. The programs are not supported by NSIDC, the distributor of this CD-ROM. Questions concerning the programs should be addressed to M.G. McPhee at the address given at the beginning and end of this file. 4.1 Program File Formats. Each program file is stored on the CD-ROM as 79-character records. The program files were padded with blanks to 79 characters in the cases where the record length was shorter or was variable. 4.2. Steps for using the complex demodulation routines in the subdirectory "PROGRAMS" follow: 4.2.1. Compile the tools modules: dcomplex.c randomio.c tricks.c mrc% cc -c dcomplex.c mrc% cc -c randomio.c mrc% cc -c tricks.c 4.2.2. Compile the "efile" program which makes a data record file from the text files, eliminating lines with asterisks (a) copy the makefile lines from efile.c to Makefile (b) make the object file mrc% make cc -c efile.c cc -o efile efile.o randomio.o tricks.o -lm 4.2.3. Compile the "fitpos" program, which performs the complex demodulation fit (it will also do a polynomial fit) on the data file made by efile (a) copy the makefile lines from fitpos.c to Makefile (b) make the object file mrc% make cc -c fitpos.c cc -c pfit4.c cc -c polyfit4.c cc -c demod4.c cc -o fitpos fitpos.o pfit4.o polyfit4.o demod4.o dcomplex.o randomio.o tricks.o -lm 4.2.4. Copy the "alpha" file from parent directory mrc% cp ../alpha 4.2.5. Run efile: mrc% efile alpha alpha 0 1989 start 82.27431 end 110.43775 fixes 680 PI Baggeroer ignore entries flagged with *? y list? n mrc% -- this produces a second data file named alpha.e that has the same information (less asterisked lines) as alpha 4.2.6. Now do the complex demodulation-- note that the time base for the phasors depends on the start time you specify, so that if you want to compare phasors from one station to another start with the same time-- if no data are present, it will fill with blanks (actually -99.0) mrc% fitpos alpha Data go from 82.274 to 110.438 Input fit start and end times (decimal day): 80 120 Input the time between fits and the fitting period:0.25 1.0 Input 0 for complex demodulation, 1 for polynomial fit: 0 Input nterm: 6 Input max error (km) (0 for no checking): 1.5 Input max time gap for successive data samples (e.g., 0.25): 0.25 Input coord system longitude offset (e.g., 30 for 30E): 0 nfits= 161 size of ff: 27048 istart,npoints: 1, 679, tref 80.000 sample at 91.245 rejected, data: (-12.07,-870.61) fit: (-10.75,-869.81) sample at 105.610 rejected, data: (-16.77,-995.43) fit: (-18.21,-993.90) The output file is named falpha.d, 80.00 to 120.00 rec 1, 80.000 (-99.00,-99.00) (-99.00,-99.00) rms: 0.000 from 0 sam 0 ************ plus output listing *********************** rec 161, 120.000 (-99.00,-99.00) (-99.00,-99.00) rms: 0.000 from 0 sam 0 4.2.7. There now exist two files spawned from the original text file, alpha: alpha.e, falpha.d, which is the file of fit coefficients. 4.2.8. These can be listed to stdout (i.e., can be redirected) with pv_list copy the makefile lines from list_pv.c to Makefile mrc% make cc -c list_pv.c cc -c fitutil.c cc -o list_pv list_pv.o fit_utilities.o dcomplex.o randomio.o tricks.o -lm 4.2.9. And run: mrc% list_pv falpha.d > alpha_hourly 5. References McPhee, M.G. (1988) Analysis and prediction of short term ice drift. Transactions of the ASME, Journal of Offshore Mechanics and Arctic Engineering, vol. 110, p. 94-100. 6. Contact Information Dr. Miles G. McPhee McPhee Research Company 450 Clover Springs Road Naches, WA 98937 USA Telephone: 509-658-2575 Omnet: M.MCPHEE Data files used to compile this data base of manned station and unmanned buoy drift positions were provided to Miles McPhee by the following CEAREX investigators: Dr. Arthur Baggeroer Massachusetts Institute of Technology Ocean Engineering Department, Room 5-204 Cambridge, MA 02139 Dr. Jean-Claude Gascard Laboratoire Oceanographie Physique Museum d'Histoire Naturelle 43 rue Cuvier 75231 Paris CEDEX 05 France Dr. James Morison Polar Science Center University of Washington 1013 NE 40th Street Seattle, WA 98105 Dr. Robin D. Muench Science Applications International Corporation 13400B Northrup Way, Suite 36 Bellevue, WA 98005 Dr. Robert Onstott Environmental Research Institute of Michigan PO Box 8618 Ann Arbor, MI 48017 Dr. James Overland NOAA PMEL 7600 Sand Point Way NE Building 3 Seattle, WA 98115 Dr. Robert Pinkel Scripps Institution of Oceanography A-025 La Jolla, CA 92093 19 October 1990 (revised 4/91)