.. _background-page:

Background Page
===============

Overview
--------

The *Background* page allows users to visualize and configure background signal subtraction for Lidar data processing. It provides visual tools, parameter inputs, and comparison with climatology to assist with accurate preprocessing.

Layout & Features
-----------------

This page includes:

1. **Channel Selection**:
   - A dropdown menu for selecting a pair of Lidar signal channels.
   - Available signals are automatically detected and paired (e.g., analog vs photon-counting).

2. **Data Visualization**:
   - Left: Raw signal data with background overlays (two channels).
   - Right: Tabbed display with:
     - **Slope**: computed slope vs climatology.
     - **Ozone**: ozone concentration profile.

3. **Parameter Configuration**:

   Each channel can be individually configured:
   - Linear regression **order**
   - Toggle for **logarithmic regression**
   - Toggle for **weighting**
   - **Minimum and maximum altitude** (with units)

4. **Actions and Buttons**:

   - **Apply new values**: tests and compares changes without modifying data.
   - **Accept**: validates changes and updates data permanently.
   - **Show Config**: reveals extra XML-based parameters.
   - **Save Config**: saves modified configuration to file.

User Workflow
-------------

1. **Select a signal pair** using the channel dropdown.
2. **Review raw signal and background subtraction** using the graphs.
3. **Adjust background calculation parameters** using the configuration panel:
   - Altitude range
   - Regression order
   - Log and weighting options
4. Click **"Apply new values"** to preview the effect.
5. If the result is satisfactory, click **"Accept"** to rerun the full preprocessing pipeline.
6. Optionally, use the **Show Config** button to inspect and edit advanced XML settings.

Graphs & Interpretation
-----------------------

- **Raw Signal Plot**:
  - Plots the raw signal from two channels.
  - Background estimation is overlaid for direct comparison.

- **Slope Plot**:
  - Shows the calculated slope compared to climatology.
  - Useful for verifying signal stability.

- **Ozone Plot**:
  - Displays the retrieved ozone profile.
  - Climatology is plotted for reference.

Saving Changes
--------------

- Configuration can be updated interactively.
- Clicking **Save Config** writes changes into the XML parameter file for future use.
- Changes are logged with timestamps for traceability.

Remarks
-------

- Altitude units and signal types are automatically adapted from the configuration.
- All changes can be undone by reloading the page or reselecting the parameter file.
- Disabled **"Accept"** button ensures no accidental data overwriting before previewing.