.. _VisNonLinearityModel:

===============================
Vis Non Linearity Model Product
===============================

Metadata
______________________

+------------------------------------------------+----------------------------------------------------------------------------------------------+
| Data product name                              | DpdVisNonLinearityModel                                                                      |
+------------------------------------------------+----------------------------------------------------------------------------------------------+
| Data product custodian                         | VIS                                                                                          |
+------------------------------------------------+----------------------------------------------------------------------------------------------+
| Name of the Schema file                        | .. raw:: html                                                                                |
|                                                |                                                                                              |
|                                                | `euc-vis-NonLinearityModel.xsd <https://gitlab.euclid-sgs.uk/ST-DM/ST_DataModel/-/blob/10.1. |
|                                                | 2/ST_DM_Schema/auxdir/ST_DM_Schema/dpd/vis/euc-vis-NonLinearityModel.xsd>`_                  |
+------------------------------------------------+----------------------------------------------------------------------------------------------+
| Processing Element(s) creating/using the data  | VIS - NonLinear Calibration                                                                  |
| product                                        |                                                                                              |
+------------------------------------------------+----------------------------------------------------------------------------------------------+
| Processing function using the data product     | VIS -- Processfield correction.                                                              |
+------------------------------------------------+----------------------------------------------------------------------------------------------+

Proposed for inclusion in EAS/SAS
==========================================
.. PFUsingStart

Yes

.. PFUsingEnd

Data product elements
=====================
+--------------+----------------------------------------------+
| Header       | object of type sys:genericHeader             |
+--------------+----------------------------------------------+
| Data         | object of type vis:visFileContainerData      |
+--------------+----------------------------------------------+
| QualityFlags | object of type dqc:sqfPlaceHolder            |
+--------------+----------------------------------------------+
| Parameters   | object of type ppr:genericKeyValueParameters |
+--------------+----------------------------------------------+
   
Detailed description of the data product
========================================
.. DetailedDescStart

Non Linearity Model is a JSON file containing a dictionary with one item per quadrant. 
This Model is produced by the Non Linearity Calibration pipeline.

There are currently two different non-linearity correction formats: 

* A up to 5th order polynomial which converts the non-linear signal to a linear signal.
* A series of points pairing a linear signal value with its corresponding non-linear signal. 

Both formats can't be mixed in the same product.

Curently (VIS PF-17), we use a TVAC model with a series of points pairing. 

For the polynomial model,  coefficients are stored in numpy.poly1d() convention, in decreasing powers, starting from the highest degree. 

Example of the polynomial product::

  "1-1.E": [
    1.6737016148821795e-32,
    -2.27198105837953e-27,
    9.851909684187759e-23,
    -1.3871686911278604e-18,
    1.0000000000000022,
    -1.204531435924529e-11
  ],
   
.. DetailedDescEnd