-
Notifications
You must be signed in to change notification settings - Fork 40
/
raw2temp.R
95 lines (80 loc) · 5.55 KB
/
raw2temp.R
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
#' @export
#'
raw2temp <-function(raw,E=1,OD=1,RTemp=20,ATemp=RTemp,IRWTemp=RTemp,IRT=1,RH=50,
PR1=21106.77,PB=1501,PF=1,PO=-7340,PR2=0.012545258,
ATA1=0.006569, ATA2=0.01262, ATB1=-0.002276, ATB2=-0.00667, ATX=1.9)
{
# how to call this function:
# raw2temp(raw,E,OD,RTemp,ATemp,IRWTemp,IRT,RH,PR1,PB,PF,PO,PR2)
# Example with all settings at default/blackbody levels
# raw2temp(18109,1,0,20,20,20,1,50,PR1,PB,PF,PO,PR2)
# example with emissivity=0.95, distance=1m, window transmission=0.96, all temperatures=20C,
# 50% relative humidity
# raw2temp(18109,0.95,1,20,20,20,0.96,50)
# default calibration constants for my FLIR camera will be used if you leave out the
# calibration data
# raw: A/D bit signal from FLIR file
# FLIR .seq files and .fcf files store data in a 16-bit encoded value.
# This means it can range from 0 up to 65535. This is referred to as the raw value.
# The raw value isactually what the sensor detects which is related to the radiance hitting
# the sensor.
# At the factory, each sensor has been calibrated against a blackbody radiation source so
# calibration values to conver the raw signal into the expected temperature of a blackbody
# radiator are provided.
# Since the sensors do not pick up all wavelengths of light, the calibration can be estimated
# using a limited version of Planck's law. But the blackbody calibration is still critical
# to this.
# E: Emissivity - default 1, should be ~0.95 to 0.97 depending on source
# OD: Object distance in metres
# RTemp: apparent reflected temperature - one value from FLIR file (oC), default 20C
# ATemp: atmospheric temperature for tranmission loss - one value from FLIR file (oC) - default = RTemp
# IRWinT: Infrared Window Temperature - default = RTemp (oC)
# IRT: Infrared Window transmission - default 1. likely ~0.95-0.96. Should be empirically determined.
# RH: Relative humidity - default 50%
# Note: PR1, PR2, PB, PF, and PO are specific to each camera and result from the calibration at factory
# of the camera's Raw data signal recording from a blackbody radiation source
# Calibration Constants (A FLIR SC660, A FLIR T300(25o), T300(telephoto), A Mikron 7515)
# PR1: PlanckR1 calibration constant from FLIR file 21106.77 14364.633 14906.216 21106.77
# PB: PlanckB calibration constant from FLIR file 1501 1385.4 1396.5 9758.743281
# PF: PlanckF calibration constant from FLIR file 1 1 1 29.37648768
# PO: PlanckO calibration constant from FLIR file -7340 -5753 -7261 1278.907078
# PR2: PlanckR2 calibration constant form FLIR file 0.012545258 0.010603162 0.010956882 0.0376637583528285
# Set constants below. Comment out those that are variables in this function
# Keep those that should remain constants.
# These are here to make troubleshooting calculations easier if not running this as a function call
# raw<-19746; E<-0.95; OD<-20; IRT<-0.96
# RTemp<-20; IRWTemp<-RTemp; ATemp<-20; RH<-50
# PR1<-21106.77; PB<-1501; PF<-1; PO<--7340; PR2<-0.012545258
# These humidity parameters were extracted from the FLIR SC660 camera
# ATA1: Atmospheric Trans Alpha 1 0.006569 constant for calculating humidity effects on transmission
# ATA2: Atmospheric Trans Alpha 2 0.012620 constant for calculating humidity effects on transmission
# ATB1: Atmospheric Trans Beta 1 -0.002276 constant for calculating humidity effects on transmission
# ATB2: Atmospheric Trans Beta 2 -0.006670 constant for calculating humidity effects on transmission
# ATX: Atmospheric Trans X 1.900000 constant for calculating humidity effects on transmission
# Equations to convert to temperature
# See http://130.15.24.88/exiftool/forum/index.php/topic,4898.60.html
# Standard equation: temperature<-PB/log(PR1/(PR2*(raw+PO))+PF)-273.15
# Other source of information: Minkina and Dudzik's Infrared Thermography: Errors and Uncertainties
emiss.wind<-1-IRT
refl.wind<-0 # anti-reflective coating on window
h2o<-(RH/100)*exp(1.5587+0.06939*(ATemp)-0.00027816*(ATemp)^2+0.00000068455*(ATemp)^3)
# converts relative humidity into water vapour pressure (I think in units mmHg)
tau1<-ATX*exp(-sqrt(OD/2)*(ATA1+ATB1*sqrt(h2o)))+(1-ATX)*exp(-sqrt(OD/2)*(ATA2+ATB2*sqrt(h2o)))
tau2<-ATX*exp(-sqrt(OD/2)*(ATA1+ATB1*sqrt(h2o)))+(1-ATX)*exp(-sqrt(OD/2)*(ATA2+ATB2*sqrt(h2o)))
# transmission through atmosphere - equations from Minkina and Dudzik's Infrared Thermography Book
# Note: for this script, we assume the thermal window is at the mid-point (OD/2) between the source
# and the camera sensor
raw.refl1<-PR1/(PR2*(exp(PB/(RTemp+273.15))-PF))-PO # radiance reflecting off the object before the window
raw.refl1.attn<-(1-E)/E*raw.refl1 # attn = the attenuated radiance (in raw units)
raw.atm1<-PR1/(PR2*(exp(PB/(ATemp+273.15))-PF))-PO # radiance from the atmosphere (before the window)
raw.atm1.attn<-(1-tau1)/E/tau1*raw.atm1 # attn = the attenuated radiance (in raw units)
raw.wind<-PR1/(PR2*(exp(PB/(IRWTemp+273.15))-PF))-PO
raw.wind.attn<-emiss.wind/E/tau1/IRT*raw.wind
raw.refl2<-PR1/(PR2*(exp(PB/(RTemp+273.15))-PF))-PO
raw.refl2.attn<-refl.wind/E/tau1/IRT*raw.refl2
raw.atm2<-PR1/(PR2*(exp(PB/(ATemp+273.15))-PF))-PO
raw.atm2.attn<-(1-tau2)/E/tau1/IRT/tau2*raw.atm2
raw.obj<-(raw/E/tau1/IRT/tau2-raw.atm1.attn-raw.atm2.attn-raw.wind.attn-raw.refl1.attn-raw.refl2.attn)
temp.C<-PB/log(PR1/(PR2*(raw.obj+PO))+PF)-273.15
temp.C
}