# mesh2node v3.2.3

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

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## Description

`mesh2node` performs **nearest-neighbor interpolation** of simulation outputs from a full mesh onto another grid's nodes. It is useful for extracting data from a high-resolution mesh to specific points or nodes defined in a separate grid file.

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## Usage

```bash
mesh2node [OPTIONS] file
```

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## Options


| Option         | Description                                                    |
| -------------- | -------------------------------------------------------------- |
| `-h`, `--help` | Display this help message and exit.                            |
| `-m <file>`    | **Mesh file**: Path to the input mesh file (required).         |
| `-n <file>`    | **Node file**: Path to the input node file (required).         |
| `-s <value>`   | **Mask value**: Value to use for masked (invalid) data points. |


> **Deprecated Options**
>
>
> | Option      | Description                                                                                          |
> | ----------- | ---------------------------------------------------------------------------------------------------- |
> | `-z <zone>` | Pre-set zone to limit the interpolation area. **This option is deprecated and no longer supported.** |
>

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## Examples

### **Basic Interpolation**

Interpolate data from `input.s2r` using `mesh.nc` and `nodes.nc`:

```bash
mesh2node -m mesh.nc -n nodes.nc input.s2r
```

### **Interpolate with Custom Mask Value**

Use a mask value of `-999.9` for invalid points:

```bash
mesh2node -m mesh.nc -n nodes.nc -s -999.9 input.s2r
```

### **Interpolate Vector Data (V2R Format)**

Interpolate vector data (e.g., velocity components) from `input.v2r`:

```bash
mesh2node -m mesh.nc -n nodes.nc input.v2r
```

### **Interpolate Complex Data (S2C Format)**

Interpolate complex harmonic constants (e.g., tidal elevation) from `input.s2c`:

```bash
mesh2node -m mesh.nc -n nodes.nc input.s2c
```

### **Interpolate Complex Vector Data (V2C Format)**

Interpolate complex vector data (e.g., tidal currents) from `input.v2c`:

```bash
mesh2node -m mesh.nc -n nodes.nc input.v2c
```

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## Environment Variables

`mesh2node` does not rely on specific environment variables. However, ensure your system has sufficient resources (memory, CPU) for large mesh or node files.

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## Notes

1. **Input Files:**
  - The **mesh file** (`-m`) and **node file** (`-n`) are **required** for interpolation.
  - Supported input file formats: `.s2r`, `.s2c`, `.v2r`, `.v2c`.
2. **Output:**
  - The output file is automatically named as `<input_file>.extraction`.
  - For example, if the input file is `data.s2r`, the output will be `data.s2r.extraction`.
3. **Masking:**
  - The `-s` option sets the value for masked (invalid) data points. The default mask value is `999.9`.
  - Masked values are assigned to nodes that fall outside the mesh or cannot be interpolated.
4. **Interpolation Method:**
  - Uses **linear interpolation** within the mesh elements to estimate values at the target nodes.
  - If a node falls outside the mesh, the mask value is assigned.
5. **Performance:**
  - For large meshes or node files, ensure sufficient memory is available.
  - The tool is optimized for **nearest-neighbor interpolation** and may not be suitable for high-order interpolation schemes.

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## See Also

- [NetCDF Tools](https://www.unidata.ucar.edu/software/netcdf/) (for handling mesh and node files)
- [Mog2D Simulation Tools](https://www.poc.obs-mip.fr/) (for related simulation outputs)