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tagwiki:tools:calibration:rough_cal_3d [2017/08/04 13:54] (current)
das39 created
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 +====== rough_cal_3d ======
 +Estimate scale factors and offsets for measurements from a triaxial field sensor.
 +-----
  
 +===== Syntax =====
 +=== Matlab & Octave ===
 +<​code>​
 +[X,G] = rough_cal_3d(X,​fstr)
 +</​code>​
 +=== R ===
 +<​code>​
 +list <- rough_cal_3d(X,​ fstr)
 +</​code>​
 +
 +===== Description =====
 +Estimate scale factors and offsets for measurements from a triaxial field sensor. This function estimates the scale factor needed to make the magnitude of X close to the expected field strength. It then calls fix_offset_3d to correct any offset errors in X. This function does not try to optimize the results. See spherical_cal for a more powerful data-driven calibration method.
 +
 +===== Inputs =====
 +^ Input var ^ Description ^ Units ^
 +| X | is a sensor structure/​list or matrix containing measurements from a triaxial field sensor such as an accelerometer or magnetometer. X can be in any units and frame.|N/A|
 +|fstr| is the expected field strength at the measurement location in the same units as X.|nT|
 +
 +===== Outputs =====
 +^ Output var ^ Description ^ Units^
 +|X| is a sensor structure/​list or matrix containing the adjusted triaxial sensor measurements. It is the same size and has the same sampling rate and units as the input data. If the input is a sensor structure/​list,​ the output will be also.|N/A|
 +|G| is a calibration structure/​list containing one field: G.polyG$poly. The first column of G.polyG$poly is the three scale factors applied to the columns of X. The second column of G.polyG$poly is the offset added to each column of X after scaling.|N/​A|
 +
 +===== Notes & assumptions =====
 +  -This function requires a lot of data as it is looking for extreme values in each axis. A minimum data size of 1000 samples should be used. This function is only usable for field sensors. It will not work for gyroscope data.
 +
 +===== Example =====
 +
 +==== Matlab & Octave ====
 +<​code>​
 +BW <- load_nc('​testset1.nc'​)
 +rcal <- rough_cal_3d(BW.M.data,​ fstr = 38.2) %fstr matches records for field strength in El Hierro when the tag was used
 +plott(rcal.X,​ BW.sampling_rate)
 +</​code>​
 +
 +==== R ====
 +<​code>​
 +BW <- beaked_whale
 +rcal <- rough_cal_3d(BW$M$data,​ fstr = 38.2) #fstr matches records for field strength in El Hierro when the tag was used
 +cal <- list(rcal = rcal$X)
 +plott(cal, BW$sampling_rate)
 +</​code>​
 +
 +===== About =====
 +[[bugs@animaltags.org]]
 +Last modified: 4 August 2017
  • tagwiki/tools/calibration/rough_cal_3d.txt
  • Last modified: 2017/08/04 13:54
  • by das39