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I don't completely understand the different coordinate systems available.  See:

I believe DTM/DTV are the ones we should assume are default, but I'm happy to be corrected.

Header Key



nameName of Amp: '0,1' 



Bounding box of physical pixels in

in assembled coordinates

GAINGainGain value of this amp e-/count1.
RDNOISEReadNoiseRead noise in counts0.
SATURATESaturationValue of saturation threshold in counts 
DTM[1-4] check mod 90 rotationReadCorner

Location of first pixel read in assembled


LINCOEFFLinearityCoeffsCoefficients of linearity fit0., 1.

Type of linearity: This could map to

a method for applying non-linearity



Bounding box of raw data (including

prescan, overscan regions)

in raw coordinates

DATASECRawDataBBoxBounding box of raw data in the raw frame 
DTM[1-4]FlipXFlip x axis when assembling?False
DTM[1-4]FlipYFlip y axis when assembling?False
DTV1, DTV2RawXYOffset

Offset of to apply to assemble raw frames

in a mosaic


Bounding box of horizontal overscan

in raw coordinates


Bounding box of vertical overscan

in raw coordinates

Empty BBox

Bounding box of prescan region

in raw coordinates

Empty BBox


Camera ConfigDescriptionDefault
nameName of the camera'FileCamera'
plateScaleplate scale at the focal plane (arcsec/mm)1.

radial coefficents that describe a

radial polynomial distortion

I think the following produces no distortion

[0, 1, 0]


Implementation of use case

I implemented the plotting use case outlined above.  The code can be found here.  The results from commit 102320d are all shown below.

Image Added

This shows an assembled flat provided by Jim C.  The segments are labeled.  Note that a bias correction and rudimentary gain correction have been applied.  This agrees with an assembled flat he provided shown here:

Image Added

Below is plotted an untrimmed version.  The green box are raw data boundaries, the red box is the overscan region and the blue box is the data region.

Image Added

The above images were produced using bounding boxes and offsets calculated in the code.  This makes the plotted images match the orientation from Jim's example.  If I use the bounding boxes in the header (commit 280194e), I get a good assembly, but it is flipped about the y-axis.  I'm not sure how important that is or what I'm missing in the headers, but I believe that the above orientation does not imply that the serial direction is +ve in the +ve x direction.

Image Added


Below is a list of questions to be addressed as a result of this requirements document.  These are just here for historical reasons.  These answers will be fleshed out in the design above.