[PIPE2D-319] Make line identification robust against wavelength shifts Created: 30/Jan/19  Updated: 29/Mar/19  Resolved: 29/Mar/19

Status: Done
Project: DRP 2-D Pipeline
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Story Priority: Normal
Reporter: price Assignee: price
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Relates
relates to PIPE2D-345 Provide a method for determining line... Done
relates to PIPE2D-340 Provide method to adjust detector map... Done

 Description   

Line identification needs to be robust against inaccuracies in the DetectorMap wavelength solution. While it's true the DetectorMap wavelength solution should be solid during observing, during development and commissioning and while dealing with both simulated data and LAM data, it's not unknown for the true wavelength solution to change relative to what's in the DetectorMap. Here's a possible algorithm:

  • find and centroid all peaks in spectrum
  • apply rough wavelength calibration to measured peaks
  • for both observed and model line lists:
    • find pairs of lines with separations between 5A and 500A (separation is not too small to allow confusion, not too large to be very non-linear)
    • for each pair, calculate mean and difference
  • match observed pairs to model pairs when the mean is within 50A and the difference is within ~ 0.5A
  • Instead of pairs, could use triplets, and match the ratio of spacings.


 Comments   
Comment by price [ 01/Mar/19 ]

I now believe that the use of this algorithm is not necessary given a decent detectorMap: when that is the case, the vanilla algorithm outperforms my implementation for HgAr (possibly due to the huge number of faint, blended lines). Nevertheless, this branch contains a lot of peripheral improvements, and the algorithm may be useful in other contexts.

Comment by hassan [ 29/Mar/19 ]

As price has mentioned, algorithm is not required in 2D DRP for its original purpose, but much of this development is expected to be useful for other functions required in 2D DRP, for example the line intensity modeling of PIPE2D-345.

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