[lsst-dm-stack-users] Pipeline and sensor routines

[Robert Lupton the Good]

> I think I now have an OK understanding of how the abstract base CmdLineTask and processImage classes etc are put together to make a commandline task like processCcd etc.

Please write it down!

>  I have two quick questions I'm a bit unclear on:
> 
> - In trying to understand the software I read the two-year old "Scientists guide to the LSST applications software".  In that document all of the pipeline tasks are described through using a clipboard and running with "runStage" etc.  I still see that code in lsst::pex::harness.  Is that code used in a different context, an alternative way of handling things, or is it now deprecated?

All that stuff is dead.  The Task approach is intended to be less abstract and more easily reused.

> - Before I write them myself I wanted to check that something like this doesn't already exist: I would like routines to determine, based on the pixel I am in etc, where I am physically located on a sensor chip (in mm or something in the reference frame of the sensor) along with constants describing the dimensions of the chip and possibly routines determining offsets from physical characteristics (like an edge).  Does anything like this already exist for the different camera descriptions?

Those exist, via cameraGeom.  An Exposure has a pointer to a Detector which knows where it is in the camera.  If you have specific questions please ask, but e.g.

    import lsst.afw.cameraGeom as cameraGeom	
    ccd = cameraGeom.cast_Ccd(exp.getDetector())

    for xy in [(0,         0),
               (width - 1, height - 1), 
               ]:
        print ccd.getPositionFromPixel(afwGeom.PointD(*xy)).getPixels(1.0)

That "getPixels()" call converts the object used to describe focal plane offsets into floats at the specified pixel scale.  The camera geom object is initialised in what are called "mm", but e.g. Subaru actually specifies offsets in 15micron pixels.

If you use the butler to read your exposure the detector will be set; if not, you'll have to look it up from the Camera -- please ask for help

						R

					R


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