# showarg v3.2.3

**Mercurial revision 5786:5c8b45563631 | 2026-08-04**

---

## Description

`showarg` displays information about a list of tidal waves or a spectrum name ([Wave Lists and Spectra](#wave-lists-spectra1)). It provides the following details for each wave:

- **Astronomic potential** (in cm)
- **Pulsation** (in degrees/hour and per hour)
- **Period** (in hours and days)
- **Critical latitude** (in degrees)
- **Doodson number**
- **Schureman notation**

If no list of waves is provided, it displays information for **all coded waves**, sorted by increasing pulsation, but **without wave separations**.

> **Note:** Wave names follow the **Darwin convention**, as described in [Schureman (1940, Table 2, pp. 164-167)](http://www.archive.org/details/manualofharmonic00schu).
> The **Doodson number** is also shown. A full list of waves with their Doodson numbers is available from the [IHO](http://www.iho.int/mtg_docs/com_wg/IHOTC/IHOTC_Misc/TWLWG_Constituent_list.pdf).

---

## Usage

```bash
showarg [OPTIONS] [sprectra] [wave1 wave2 ...]
```

---

## Options

| Option | Description |
|--------|-------------|
| `-h`, `--help` | Display help and exit. |
| `--astronomic` | Specify the astronomic angle convention: `linearSchureman`, `Meeus`, `AVISO-FES-2.9.5`, or `AVISO_SOLID_TIDES`. |
| `--alias <frequency>` | Specify an aliasing frequency (in days). **Not compatible** with `--combinations`. |
| `--combinations` | Show non-linear combinations of all astronomic waves. **Not compatible** with `--alias`. Ignored if a list of waves is provided. |
| `--full-accuracy` | Enable maximum number of digits for output precision. |
| `-s <date>` | Start date in `dd/mm/yyyy` format. |
| `-f <date>` | End date in `dd/mm/yyyy` format. |
| `-a` | Show astronomic arguments periodically (default: daily). See `-i` for frequency. |
| `-i <frequency>` | Specify the daily frequency for displaying arguments (minimum: daily). Implies `-a`. |

---

(wave-lists-spectra1)=
## Wave Lists and Spectra

You can specify:
1. **Individual waves** (e.g., `M2`, `S2`, `O1`, `K1`). Run `showarg` without arguments to see the full list of available waves.
2. **Predefined spectra**:
   - `ESTUARINE`
   - `ESTUARINE-HF`
   - `COMODO`
   - `COASTAL`
   - `COASTAL-HF`
   - `SHELF`
   - `SHELF-HF`
   - `DEEP`
   - `DEEP-HF`
   - `REDUCED`
   - `CURRENTS-HF`
   - `FES2022c`
   - `AVISO-FES-SP`
   - `AVISO-FES-ADMITTANCE`
   - `AVISO-FES-LP`
   - `AVISO-FES-LP-PROXY`

---

## Examples

### **Display Information for Specific Waves**
Show details for waves `M2`, `S2`, `O1`, and `K1`:
```bash
showarg M2 S2 O1 K1
```

### **Display All Coded Waves**
List all available waves with their properties:
```bash
showarg
```

### **Use Aliasing Frequency**
Show waves with an aliasing frequency of **9.9156 days** (e.g., for TPJason TPN):
```bash
showarg --alias 9.9156
```

Show waves with an aliasing frequency of **0.99349 days** (e.g., for SWOT CalVal orbits):
```bash
showarg --alias 0.99349
```

Show waves with an aliasing frequency of **20.86455 days**:
```bash
showarg --alias 20.86455
```

### **Show Non-Linear Combinations**
Display non-linear combinations of all astronomic waves:
```bash
showarg --combinations
```

### **Display Arguments for a Date Range**
Show astronomic arguments daily from **01/01/2020** to **31/12/2020**:
```bash
showarg -s 01/01/2020 -f 31/12/2020 -a
```

Show astronomic arguments every **6 hours** for the same period:
```bash
showarg -s 01/01/2020 -f 31/12/2020 -a -i 4
```

### **Use a Predefined Spectrum**
Display waves from the `COMODO` spectrum:
```bash
showarg --spectrum COMODO
```

### **High-Precision Output**
Enable maximum precision for wave properties:
```bash
showarg --full-accuracy M2 S2
```

---

## Environment Variables

`showarg` does not use environment variables for its core functionality. However, it relies on standard system libraries for date and time handling.

---

## Notes

1. **Wave Naming Convention**: All wave names follow the **Darwin convention** as referenced in Schureman (1940).
2. **Doodson Numbers**: The Doodson number is a unique identifier for each tidal constituent, based on its astronomical origins.
3. **Schureman Notation**: Provides a detailed breakdown of the wave's astronomical components (e.g., `degree=2: T=2 s=-2 h=2 p=0 p1=0`).
4. **Aliasing**: Use `--alias` to simulate the effect of aliasing for specific missions (e.g., satellite orbits).
5. **Combinations**: The `--combinations` option is useful for studying non-linear interactions between waves.
6. **Output Format**: By default, separations are shown only if a list of waves is provided. For all waves, separations are omitted.

---

## See Also

- [Schureman (1940) - Manual of Harmonic Analysis and Prediction of Tides](http://www.archive.org/details/manualofharmonic00schu)
- [IHO Tidal Wave Constituent List](http://www.iho.int/mtg_docs/com_wg/IHOTC/IHOTC_Misc/TWLWG_Constituent_list.pdf)
- [AVISO Altimetry Missions](https://www.aviso.altimetry.fr/en/missions.html)