This documents the deep sonar files archived to JOSS in October 1999. The files in this folder are 3 hour averages of ice/water relative velocity. The velocities are in centimeters per second. They were taken using two sonar systems - a 140 Khz sonar (pre-spring 1998), and a 161 Khz sonar (after-spring 1998). All data that was not noise or contaminated by CTD hits is included here. The data is in Matlab format. Data in each file was saved with the variable name x. There is another set of files that are ascii files submitted as part of this archive, and can be requested if the user does not have access to Matlab. Two depth axis files are included, one for each sonar. Depth axis in meters. The 140 had 229 bins, of 2.13 meters width, and the 161 had 205 bins, also of 2.13 meters width. The relative velocity files therefore have a different number of rows, depending on the system. The depth axis for the 140 Khz sonar may be found in the file depth140.mat, while the depth axis for the 161Khz sonar may be found in depth161.mat The relative velocities are not true north/south velocities, but are relative to magnetic north. The North magnetic pole is assumed to be the y axis. Therefore, the current direction measured clockwise from magnetic north would be: direction=atan(xvel/yvel); See the caution at the end of this file regarding the heading. The file naming convention is as follows: mrel_averaging time_sonartype_1997yearday.mat For example, one of the sonar files is: mrel_3hr_140_330.mat The list of files, and the amount of time each covers, are listed below: mrel_3hr_140_330.mat - 12.625 days mrel_3hr_140_343.mat - 18.875 days mrel_3hr_140_364.mat - 0.5 days mrel_3hr_140_367.mat - 3.375 days mrel_3hr_140_371.mat - 10.25 days mrel_3hr_140_385.mat - 3.25 days mrel_3hr_140_390.mat - 11.375 days mrel_3hr_161_458.mat - 4 days mrel_3hr_161_518.mat - 3.25 days mrel_3hr_161_522.mat - 27 days mrel_3hr_161_605.mat - 9.875 days mrel_3hr_161_586.mat - 6.625 days mrel_3hr_161_625.mat - 1.875 days mrel_3hr_161_627.mat - 13.75 days mrel_3hr_161_615.mat - 9.25 days The bin width for each sonar was 2.13 meters. Each sonar had a different number of bins. The depth axis for the 140 Khz sonar may be found in the file depth140.mat, while the depth axis for the 161Khz sonar may be found in depth161.mat . Each depth in the files is the center of its particular bin. The axes were saved with the variable name depthaxis. Each column of the velocity file consists of number of rows which include a header, the east/west velocity at each depth, and then the north/south veocity at each depth. The header consists of 4 lines: 1. timestamp - yearday 1997 - Jan 1., 1997, noon Greenwich = yearday 1.5 2. latitude - degrees north 3. longitude - degrees west 4. declination predicted by math model. Declination measurement: The declination is from the geomagnetic models - the one I used was the Canadian Geomagnetic Reference Field Model - which can be found on the web at http://www.geolab.nrcan.gc.ca/geomag/e_cgrf.html . The other models (IGRF, etc.) all gave results within a couple of degrees of this one. Based on the above model, I derived the following approximation for the declination: // dec=(-0.7638*lon)+(1.1734*(lat-75.58))+146.3895 // // It is generally accurate to within a degree of the values predicted by the math model. // // Latitude specified in degrees north here, longitude in degrees west. There are four primary cautions one should use when looking at this data. 1. Bottom hits: Care should be taken when examining the velocity records in shallow water. Examples of aliased bottom hits may be seen (for example, near 300 meters on day 524, and near 130 meters on day 541.6 - both of these in file mrel_3hr_161_522.mat). 2. Do not use the first few bins: The first few depth bins (roughly 5) should not be trusted. The transducer is still ringing from the sound transmission. This can be seen by overlaying the relative velocities at each depth as a function of time on the same plot. 3. Extremely deep data bins should not be trusted: Data bins near the end of the depth axis are noisy. This "noise floor" fluctuates throughout the drift, and is usually apparent upon examination of the data. For example, data below roughly 350 meters in the file mrel_3hr_161_343.mat starts to exhibit signs of noise. 4. The current heading may be off by 10 degrees with the 140, and up to 15 degrees with the 161. This became evident when comparing our data with Miles McPhee's turbulence mast data. The issue is unresolved, but one "quick fix" that gets them to match is to subtract 10 degrees from the 140 current directions, and subtract 15 degrees from the 161 current directions. Clockwise is defined as positive for this operation. the following matlab script may be helpful to access the data: ******* function [timeout,latout,lonout,decout,xrel,yrel]=loadrvelfile(filein); % % [timeout,latout,lonout,decout,xrel,yrel]=loadrvelfile(filein); % % will load a 3 hour JOSS file and return the time, latitude, longitude, declination, % relative x velocities, and relative y velocities to the user. % % filein should be in single quotes % headsize=4; % % do it all at once % trow=1; latrow=2; lonrow=3; decrow=4; % eval(['load ',filein]); % timeout=x(trow,:); latout=x(latrow,:); lonout=x(lonrow,:); decout=x(decrow,:); % [mx,nx]=size(x); numbins=(mx-headsize)/2; % xrel=x(headsize+1:headsize+numbins,:); yrel=x(headsize+numbins+1:mx,:); % % routine is ended % ************* Questions?? Contact information: (1) Rob Pinkel phone: (619) 534-2056 email: rpinkel@ucsd.edu (2) Chris Halle phone: (619) 534-6966 email: challe@opg1.ucsd.edu Contents of file depth140.txt follow----------------------------------------- 1.0650000e+00 3.1950000e+00 5.3250000e+00 7.4550000e+00 9.5850000e+00 1.1715000e+01 1.3845000e+01 1.5975000e+01 1.8105000e+01 2.0235000e+01 2.2365000e+01 2.4495000e+01 2.6625000e+01 2.8755000e+01 3.0885000e+01 3.3015000e+01 3.5145000e+01 3.7275000e+01 3.9405000e+01 4.1535000e+01 4.3665000e+01 4.5795000e+01 4.7925000e+01 5.0055000e+01 5.2185000e+01 5.4315000e+01 5.6445000e+01 5.8575000e+01 6.0705000e+01 6.2835000e+01 6.4965000e+01 6.7095000e+01 6.9225000e+01 7.1355000e+01 7.3485000e+01 7.5615000e+01 7.7745000e+01 7.9875000e+01 8.2005000e+01 8.4135000e+01 8.6265000e+01 8.8395000e+01 9.0525000e+01 9.2655000e+01 9.4785000e+01 9.6915000e+01 9.9045000e+01 1.0117500e+02 1.0330500e+02 1.0543500e+02 1.0756500e+02 1.0969500e+02 1.1182500e+02 1.1395500e+02 1.1608500e+02 1.1821500e+02 1.2034500e+02 1.2247500e+02 1.2460500e+02 1.2673500e+02 1.2886500e+02 1.3099500e+02 1.3312500e+02 1.3525500e+02 1.3738500e+02 1.3951500e+02 1.4164500e+02 1.4377500e+02 1.4590500e+02 1.4803500e+02 1.5016500e+02 1.5229500e+02 1.5442500e+02 1.5655500e+02 1.5868500e+02 1.6081500e+02 1.6294500e+02 1.6507500e+02 1.6720500e+02 1.6933500e+02 1.7146500e+02 1.7359500e+02 1.7572500e+02 1.7785500e+02 1.7998500e+02 1.8211500e+02 1.8424500e+02 1.8637500e+02 1.8850500e+02 1.9063500e+02 1.9276500e+02 1.9489500e+02 1.9702500e+02 1.9915500e+02 2.0128500e+02 2.0341500e+02 2.0554500e+02 2.0767500e+02 2.0980500e+02 2.1193500e+02 2.1406500e+02 2.1619500e+02 2.1832500e+02 2.2045500e+02 2.2258500e+02 2.2471500e+02 2.2684500e+02 2.2897500e+02 2.3110500e+02 2.3323500e+02 2.3536500e+02 2.3749500e+02 2.3962500e+02 2.4175500e+02 2.4388500e+02 2.4601500e+02 2.4814500e+02 2.5027500e+02 2.5240500e+02 2.5453500e+02 2.5666500e+02 2.5879500e+02 2.6092500e+02 2.6305500e+02 2.6518500e+02 2.6731500e+02 2.6944500e+02 2.7157500e+02 2.7370500e+02 2.7583500e+02 2.7796500e+02 2.8009500e+02 2.8222500e+02 2.8435500e+02 2.8648500e+02 2.8861500e+02 2.9074500e+02 2.9287500e+02 2.9500500e+02 2.9713500e+02 2.9926500e+02 3.0139500e+02 3.0352500e+02 3.0565500e+02 3.0778500e+02 3.0991500e+02 3.1204500e+02 3.1417500e+02 3.1630500e+02 3.1843500e+02 3.2056500e+02 3.2269500e+02 3.2482500e+02 3.2695500e+02 3.2908500e+02 3.3121500e+02 3.3334500e+02 3.3547500e+02 3.3760500e+02 3.3973500e+02 3.4186500e+02 3.4399500e+02 3.4612500e+02 3.4825500e+02 3.5038500e+02 3.5251500e+02 3.5464500e+02 3.5677500e+02 3.5890500e+02 3.6103500e+02 3.6316500e+02 3.6529500e+02 3.6742500e+02 3.6955500e+02 3.7168500e+02 3.7381500e+02 3.7594500e+02 3.7807500e+02 3.8020500e+02 3.8233500e+02 3.8446500e+02 3.8659500e+02 3.8872500e+02 3.9085500e+02 3.9298500e+02 3.9511500e+02 3.9724500e+02 3.9937500e+02 4.0150500e+02 4.0363500e+02 4.0576500e+02 4.0789500e+02 4.1002500e+02 4.1215500e+02 4.1428500e+02 4.1641500e+02 4.1854500e+02 4.2067500e+02 4.2280500e+02 4.2493500e+02 4.2706500e+02 4.2919500e+02 4.3132500e+02 4.3345500e+02 4.3558500e+02 4.3771500e+02 4.3984500e+02 4.4197500e+02 4.4410500e+02 4.4623500e+02 4.4836500e+02 4.5049500e+02 4.5262500e+02 4.5475500e+02 4.5688500e+02 4.5901500e+02 4.6114500e+02 4.6327500e+02 4.6540500e+02 4.6753500e+02 4.6966500e+02 4.7179500e+02 4.7392500e+02 4.7605500e+02 4.7818500e+02 4.8031500e+02 4.8244500e+02 4.8457500e+02 4.8670500e+02 End of file depth140.txt-------------------------------------------------------- Contents of file depth161.txt follow-------------------------------------------- 1.0650000e+00 3.1950000e+00 5.3250000e+00 7.4550000e+00 9.5850000e+00 1.1715000e+01 1.3845000e+01 1.5975000e+01 1.8105000e+01 2.0235000e+01 2.2365000e+01 2.4495000e+01 2.6625000e+01 2.8755000e+01 3.0885000e+01 3.3015000e+01 3.5145000e+01 3.7275000e+01 3.9405000e+01 4.1535000e+01 4.3665000e+01 4.5795000e+01 4.7925000e+01 5.0055000e+01 5.2185000e+01 5.4315000e+01 5.6445000e+01 5.8575000e+01 6.0705000e+01 6.2835000e+01 6.4965000e+01 6.7095000e+01 6.9225000e+01 7.1355000e+01 7.3485000e+01 7.5615000e+01 7.7745000e+01 7.9875000e+01 8.2005000e+01 8.4135000e+01 8.6265000e+01 8.8395000e+01 9.0525000e+01 9.2655000e+01 9.4785000e+01 9.6915000e+01 9.9045000e+01 1.0117500e+02 1.0330500e+02 1.0543500e+02 1.0756500e+02 1.0969500e+02 1.1182500e+02 1.1395500e+02 1.1608500e+02 1.1821500e+02 1.2034500e+02 1.2247500e+02 1.2460500e+02 1.2673500e+02 1.2886500e+02 1.3099500e+02 1.3312500e+02 1.3525500e+02 1.3738500e+02 1.3951500e+02 1.4164500e+02 1.4377500e+02 1.4590500e+02 1.4803500e+02 1.5016500e+02 1.5229500e+02 1.5442500e+02 1.5655500e+02 1.5868500e+02 1.6081500e+02 1.6294500e+02 1.6507500e+02 1.6720500e+02 1.6933500e+02 1.7146500e+02 1.7359500e+02 1.7572500e+02 1.7785500e+02 1.7998500e+02 1.8211500e+02 1.8424500e+02 1.8637500e+02 1.8850500e+02 1.9063500e+02 1.9276500e+02 1.9489500e+02 1.9702500e+02 1.9915500e+02 2.0128500e+02 2.0341500e+02 2.0554500e+02 2.0767500e+02 2.0980500e+02 2.1193500e+02 2.1406500e+02 2.1619500e+02 2.1832500e+02 2.2045500e+02 2.2258500e+02 2.2471500e+02 2.2684500e+02 2.2897500e+02 2.3110500e+02 2.3323500e+02 2.3536500e+02 2.3749500e+02 2.3962500e+02 2.4175500e+02 2.4388500e+02 2.4601500e+02 2.4814500e+02 2.5027500e+02 2.5240500e+02 2.5453500e+02 2.5666500e+02 2.5879500e+02 2.6092500e+02 2.6305500e+02 2.6518500e+02 2.6731500e+02 2.6944500e+02 2.7157500e+02 2.7370500e+02 2.7583500e+02 2.7796500e+02 2.8009500e+02 2.8222500e+02 2.8435500e+02 2.8648500e+02 2.8861500e+02 2.9074500e+02 2.9287500e+02 2.9500500e+02 2.9713500e+02 2.9926500e+02 3.0139500e+02 3.0352500e+02 3.0565500e+02 3.0778500e+02 3.0991500e+02 3.1204500e+02 3.1417500e+02 3.1630500e+02 3.1843500e+02 3.2056500e+02 3.2269500e+02 3.2482500e+02 3.2695500e+02 3.2908500e+02 3.3121500e+02 3.3334500e+02 3.3547500e+02 3.3760500e+02 3.3973500e+02 3.4186500e+02 3.4399500e+02 3.4612500e+02 3.4825500e+02 3.5038500e+02 3.5251500e+02 3.5464500e+02 3.5677500e+02 3.5890500e+02 3.6103500e+02 3.6316500e+02 3.6529500e+02 3.6742500e+02 3.6955500e+02 3.7168500e+02 3.7381500e+02 3.7594500e+02 3.7807500e+02 3.8020500e+02 3.8233500e+02 3.8446500e+02 3.8659500e+02 3.8872500e+02 3.9085500e+02 3.9298500e+02 3.9511500e+02 3.9724500e+02 3.9937500e+02 4.0150500e+02 4.0363500e+02 4.0576500e+02 4.0789500e+02 4.1002500e+02 4.1215500e+02 4.1428500e+02 4.1641500e+02 4.1854500e+02 4.2067500e+02 4.2280500e+02 4.2493500e+02 4.2706500e+02 4.2919500e+02 4.3132500e+02 4.3345500e+02 4.3558500e+02 End of file depth161.txt--------------------------------------------------------