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computeabsorption.py
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computeabsorption.py
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#name: computeAbsorption
#created: July 2017
#by: [email protected]
#description: python module to compute the absorption of sound in seawater, and read a CTD probe CSV file.
import os.path
import struct
import pprint
import time
import datetime
import math
import random
from datetime import datetime
from datetime import timedelta
from statistics import mean
import csv
########################################
def main():
# filename = "F:/Projects/multispectral/DataRev2/V2 - Aug 2017/20170526 - NEWBEX/CTD/025348_2017-05-24_13-17-00Down .csv"
# filename = "F:/Projects/multispectral/DataRev2/V2 - Aug 2017/20170526 - NEWBEX/CTD/025348_2017-05-24_13-17-00Up .csv"
filename = "F:/Projects/multispectral/DataRev2/V2 - Aug 2017/Bedford Basin/20170502 - CTD/CTD 025348_2017-04-30_17-13-05.csv"
with open(filename, 'r') as csvfile:
reader = csv.reader(csvfile, delimiter=',', quotechar='|')
for row in reader:
if len(row) == 0:
continue
if row[0].startswith('2017'):
conductivity = float(row[2]) * 1000
temperature = float(row[3])
depth = float(row[4])
salinity = computesalinity(conductivity, temperature)
absorption100 = computAbsorption(100, temperature, salinity, depth)
absorption200 = computAbsorption(200, temperature, salinity, depth)
absorption400 = computAbsorption(400, temperature, salinity, depth)
print("%.3f,%.3f,%.3f,%.3f,%.3f,%.3f" %(temperature, salinity, depth, absorption100, absorption200, absorption400))
return
#Pressure (Decibar),Depth (Meter),Temperature (Celsius),Conductivity (MicroSiemens per Centimeter),Specific conductance (MicroSiemens per Centimeter),Salinity (Practical Salinity Scale),Sound velocity (Meters per Second),Density (Kilograms per Cubic Meter)
filename = "F:/Projects/multispectral/DataRev2/V2 - Aug 2017/20161130 - Patricia Bay/CTD/CC1345004_20161129_201702.csv"
with open(filename, 'r') as csvfile:
reader = csv.reader(csvfile, delimiter=',', quotechar='|')
for row in reader:
if row[0].startswith('%'):
continue
if row[0].startswith('P'):
continue
temperature = float(row[2])
salinity = float(row[5])
depth = float(row[1])
# print(row)
absorption100 = computAbsorption(100, temperature, salinity, depth)
absorption200 = computAbsorption(200, temperature, salinity, depth)
absorption400 = computAbsorption(400, temperature, salinity, depth)
print("%.3f,%.3f,%.3f,%.3f,%.3f,%.3f" %(temperature, salinity, depth, absorption100, absorption200, absorption400))
########################################
#from: view-source:http:#resource.npl.co.uk/acoustics/techguides/seaabsorption/
def computAbsorption(frequency=1, temperature=8, salinity=35, depth=50, pH=8):
'''compute the absoption of sound in seawater using the AinslieMcColm algortithm'''
# calculation of absorption according to:
# Ainslie & McColm, J. Acoust. Soc. Am., Vol. 103, No. 3, March 1998
# f frequency (kHz)
# T Temperature (degC)
# S Salinity (ppt)
# D Depth (metres)
# pH Acidity
# # Total absorption = Boric Acid Contrib. + Magnesium Sulphate Contrib. + Pure Water Contrib.
Boric = 0 # boric acid contribution
MgSO4 = 0 # magnesium sulphate contribution
H2O = 0 # pure water contribution
Alpha = 0 # total absorption (dB/km)
T_kel = 0 # ambient temperature (Kelvin)
A1 = 0 # (dB/km/kHz)
A2 = 0 # (dB/km/kHz)
A3 = 0 # (dB/km/kHz)
P1 = 0 # pressure correction factor
P2 = 0 #
P3 = 0 #
frequency1 = 0 # (kHz)
frequency2 = 0 # (kHz)
Kelvin = 273.1 # for converting to Kelvin (273.15)
depth = depth / 1000
# Measured ambient temp
T_kel = Kelvin + temperature
# Boric acid contribution
A1 = 0.106 * math.exp((pH - 8)/0.56)
P1 = 1
frequency1 = 0.78 * math.sqrt(salinity / 35) * math.exp(temperature/26)
Boric = (A1 * P1 * frequency1 * frequency**2)/(frequency**2 + frequency1**2)
# MgSO4 contribution
A2 = 0.52 * (salinity / 35) * (1 + temperature/43)
P2 = math.exp(-depth/6)
frequency2 = 42 * math.exp(temperature/17)
MgSO4 = (A2 * P2 * frequency2 * frequency**2)/(frequency**2 + frequency2**2)
# Pure water contribution
A3 = 0.00049*math.exp(-(temperature/27 + depth/17))
P3 = 1
H2O = A3 * P3 * frequency**2
# Total absorption (dB/km)
Alpha = Boric + MgSO4 + H2O
return Alpha
########################################
def computesalinity(conductivity=35000, temperature=10):
'''gives salinity (psu)
as a function of conductivity (micro S/cm)and temperature(C)
rounded to nearest tenth of a psu
code adapted from c-code found at http://www.fivecreeks.org/monitor/sal.html
or see Standard Methods for the Examination of Water and Wastewater
dps - Feb 17, 2003'''
a0=0.008
a1=-0.1692
a2=25.3851
a3=14.0941
a4=-7.0261
a5=2.7081
b0=0.0005
b1=-0.0056
b2=-0.0066
b3=-0.0375
b4=0.0636
b5=-0.0144
c0=0.6766097
c1=0.0200564
c2=0.0001104259
c3=-0.00000069698
c4=0.0000000010031
if (temperature < 0 or 30 < temperature):
return None
if (conductivity <= 0):
sal="Out of range"
r=conductivity/42914
r /= (c0 + temperature * (c1 + temperature * (c2 + temperature * (c3 + temperature * c4))))
r2=math.sqrt(r)
ds=b0+r2*(b1+r2*(b2+r2*(b3+r2*(b4+r2*b5))))
ds*=((temperature-15.0)/(1.0+0.0162*(temperature-15.0)))
salinity=a0+r2*(a1+r2*(a2+r2*(a3+r2*(a4+r2*a5))))+ds
return salinity
########################################
if __name__ == "__main__":
main()