# Topographic position
<!-- <div class="algorithm-id">
<strong>Algorithm ID</strong>: <code>hedgetools:topographicposition</code>
</div> -->
```{container} algorithm-id
**Algorithm ID**: `hedgetools:topographicposition`
```

This tool is based on **GRASS GIS's Geomorphons**. For more details, you can consult the tool's help page: [r.geomorphon](https://grass.osgeo.org/grass83/manuals/r.geomorphon.html).

The algorithm assigns to each hedge the **main topographic position** it occupies. Geomorphon detects **10 categories**: **Flat, Peak, Ridge, Shoulder, Spur, Slope, Hollow, Footslope, Valley, Pit.**

```{note}
It is recommended not to use a DTM with very high resolution, as it may create numerous small topographic variations, introducing noise in the results.
```

```{note}
Since hedges can traverse multiple topographic forms, it is recommended to split them first using the [Split by Interval](../data_transformation/split_by_interval.md) algorithm.
```

## Parameters

| Label | Name | Type | Description |
|-------|------|------|-------------|
| Input polygon layer | `INPUT` | [vector: polygon] | Polygon vector layer representing the hedges. |
| Input elevation raster (DTM) | `RASTER` | [raster] | Digital Terrain Model describing the ground elevation without obstacles. |
| Elevation band | `BAND` | [raster band] <br> Default: 1 | Elevation band of the DTM raster in case of multiband. |
| Search radius (meters) | `SEARCH` | [numeric: double] <br> Default: 100.0 | Maximum distance around each cell used by the geomorphon algorithm to define the surrounding topography. |
| Skip radius (meters) | `SKIP` | [numeric: double] <br> Default: 50.0 | Distance used by the topography algorithm to ignore small irregularities when constructing topographic forms. |
| Kernel size (pixels) | `KERNEL_SIZE` | [numeric: integer] <br> Default: 7 | Kernel size of the median filter applied after geomorphon analysis to smooth local variations. Must be odd. Larger kernels remove more noise. |
| Output topographic position layer | `OUTPUT` | [vector: polygon] <br> Default: `[Create temporary layer]` | Output polygon vector layer. |

## Outputs

| Label | Name | Type | Description |
|-------|------|------|-------------|
| Output topographic position layer | `OUTPUT` | [vector: polygon] | Polygon vector layer with a new field `topo_position` indicating the main topographic position of hedges. |