# 2 - Topological node
<!-- <div class="algorithm-id">
<strong>Algorithm ID</strong>: <code>hedgetools:topologicalnode</code>
</div> -->
```{container} algorithm-id
**Algorithm ID**: `hedgetools:topologicalnode`
```

This tool takes line geometries created from [Topological arc](topological_arc.md) and generates nodes at their junctions and extremities.

![](../../../images/data_preparation/topological_node/topological_node.png)

Nodes are characterized by their degree and associated node type:

| Degree | Node type | Description |
|-------|------|-------------|
| 1 | O |  Node at the extremitry of a line |
| 3 | T | Node at a junction between three lines |
| 4 | X | Node at a junction between four lines |
| 5+ | M | Node at a junction between 5 or more lines |

## Parameters

| Label | Name | Type | Description |
|-------|------|------|-------------|
| Input arc layer | `INPUT` | [vector: line] | Line vector layer with a `pid` and `eid` fields to create the nodes from. |
| Output arc layer | `OUTPUT_ARC` | [vector: line] <br> Default: `[Create temporary layer]` | Output line vector layer |
| Output node layer | `OUTPUT_NODE` | [vector: point] <br> Default: `[Create temporary layer]` | Output point vector layer |

## Outputs

| Label | Name | Type | Description |
|-------|------|------|-------------|
| Output arc layer | `OUTPUT_ARC` | [vector: line] | Line vector layer of the main median axis with a `src_vid` (FK) and a `tgt_vid` (FK) field. |
| Output node layer | `OUTPUT_NODE` | [vector: point] | Point vector layer with a `vid` (PK), `degree` and `node_type` field. |