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# Non-Vertical Scan Documentation

This section documents the **non-vertical Doppler lidar scan products** currently handled within the production conversion workflow.

At present, the non-vertical workflow is focused on the **DL141 User5 scan files** found in:

```text

/lafi/doppler_vertical_GOP/DL_141_vertical_until_17_june_2025/Proc/2025

```

These files differ from the vertical-stare datasets documented under [`vertical_scan/`](../vertical_scan/) because they represent **directed scanning geometries** rather than near-vertical profiling.

## Scope of this section

This documentation complements, rather than duplicates, the vertical-scan documentation.

In particular:

- General project context is documented in the parent [`README.md`](../README.md).

- The general CF metadata philosophy is documented in the vertical-scan page [`vertical_scan/cf_metadata_strategy.md`](../vertical_scan/cf_metadata_strategy.md).

- This non-vertical section focuses only on:

  - the specific scan families identified in the DL141 User5 data,

  - the processing choices that differ from the vertical-scan case,

  - the structure of the Level-1 and aggregated daily products,

  - known exceptions and deferred issues.

## Recommended contents

This section is organised into the following pages:

1. **[`dataset_overview.md`](./dataset_overview.md)**  

   Overview of the non-vertical datasets currently identified, with emphasis on the DL141 User5 scans.

2. **[`processing_differences_from_vertical_scan.md`](./processing_differences_from_vertical_scan.md)**  

   A concise explanation of how the non-vertical workflow differs from the vertical-scan workflow.

3. **[`exceptions_and_follow_up.md`](./exceptions_and_follow_up.md)**  

   Notes on exceptional files, deferred interpretation issues, and items to revisit later.

## Current status of non-vertical scan handling

### Dataset presently addressed

The currently documented non-vertical workflow covers the **DL141 User5 scan family**.

Based on scan inventory and geometry checks, the regular User5 files comprise two main scan types:

- `DL_DIAL_north - csm`

- `DL_DIAL_south - csm`

These are interpreted operationally as **fixed-azimuth elevation scans**.

### Key identified characteristics

- **Instrument/system ID:** `141`

- **Filename family:** `User5_141_*.hpl`

- **Regular observation date:** `2025-06-17`

- **Typical azimuth:** approximately `330°`

- **Typical elevation sweep:** approximately `-0.5°` to `9.74°`

- **Typical range-gate count:** `100`

- **Typical range-gate length:** `30 m`

- **Typical pulses per ray:** `3000`

- **Typical rays per file:** around `61–62`, with small variation across files

### Aggregated output currently expected

For the regular User5 files, the workflow produces:

- **source-aligned Level-1 NetCDF files** (one per HPL file),

- **daily aggregated Level-1 NetCDF files**, separated by scan family,

- **CF-oriented daily NetCDF files**, still without range-gate geolocation.

At present, the regular User5 files yield two daily products for `2025-06-17`:

- one **north** daily file,

- one **south** daily file.

## Relationship to the vertical-scan documentation

The non-vertical workflow intentionally reuses as much of the vertical-scan design as possible:

- preservation-oriented Level-1 conversion,

- retention of all parseable source rays and non-negative gates,

- daily aggregation with provenance tracking,

- subsequent CF-oriented metadata application.

However, non-vertical scans require different treatment with respect to **geometry interpretation** and **CF representation**. These differences are documented in [`processing_differences_from_vertical_scan.md`](./processing_differences_from_vertical_scan.md).

## Notes for future extension

This section is written so that additional non-vertical scan families can later be added, for example:

- other directed-scan families from DL141,

- future non-vertical scans from DL011 or DL262,

- scans requiring different beam-geometry interpretation.

If that happens, this section can be extended with new instrument-specific or scan-family-specific subsections while keeping the overall structure the same.