Dutch Portolan Demo

# Navigation Locks — Rijkswaterstaat / Netherlands

## What This Dataset Is

Point locations of **92 navigation locks** (sluizen) on the Dutch recreational waterway network.
Each lock includes its name, location, number of chambers, VHF radio channel, operator
information, and contact details.

Locks are essential infrastructure in the Netherlands, allowing vessels to move between
waterways at different water levels. This dataset covers locks on the recreational network
managed by various authorities including Rijkswaterstaat, provinces, and municipalities.

**Provider:** Rijkswaterstaat (Directorate-General for Public Works and Water Management)
**License:** Public domain (Dutch government open data)

## How to Access

The data is a GeoParquet file in **EPSG:28992** (Amersfoort / RD New). Use DuckDB with the
spatial extension.

```python
import duckdb

con = duckdb.connect()
con.execute("INSTALL spatial; LOAD spatial;")

URL = 'https://data.source.coop/cholmes/portolan-nl/rijkswaterstaat/sluizen/sluizen.parquet'

df = con.execute(f"""
    SELECT * FROM read_parquet('{URL}')
    LIMIT 5
""").df()
```

The file is tiny (92 features) — loads instantly.

## Schema — Field Meanings

| Field | Type | Meaning |
|-------|------|---------|
| `geometry` | WKB Point | Lock location in **EPSG:28992**. |
| `NAAM` | string | **Lock name** (e.g., "Sluis Maasbracht", "Beatrixsluis"). |
| `PLAATSNAAM` | string | **City/town** where the lock is located. |
| `NR_KOLKEN` | int/float | **Number of chambers** (1–4). More chambers = higher capacity. |
| `MARIFOONKA` | string | **VHF radio channel** for contacting the lock operator. |
| `VRT_CODE` | string | Waterway code (vaarweg code). |
| `VRTNAAM` | string | **Waterway name** (vaarweg naam). |
| `BHR_NAAM` | string | **Operator name** — the organization that manages the lock. |
| `BHR_TYPE` | string | **Operator type** (e.g., government, province, municipality). |
| `TEL_NR` | string | Phone number for the lock operator. |

## Useful Query Patterns

### List all locks with their waterways

```sql
SELECT NAAM, PLAATSNAAM, VRTNAAM, NR_KOLKEN
FROM read_parquet('https://data.source.coop/cholmes/portolan-nl/rijkswaterstaat/sluizen/sluizen.parquet')
ORDER BY NAAM
```

### Group locks by operator

```sql
SELECT BHR_NAAM, BHR_TYPE, COUNT(*) AS locks
FROM read_parquet('https://data.source.coop/cholmes/portolan-nl/rijkswaterstaat/sluizen/sluizen.parquet')
GROUP BY BHR_NAAM, BHR_TYPE
ORDER BY locks DESC
```

### Find multi-chamber locks (highest capacity)

```sql
SELECT NAAM, PLAATSNAAM, VRTNAAM, NR_KOLKEN
FROM read_parquet('https://data.source.coop/cholmes/portolan-nl/rijkswaterstaat/sluizen/sluizen.parquet')
WHERE NR_KOLKEN >= 2
ORDER BY NR_KOLKEN DESC
```

### Locks by waterway

```sql
SELECT VRTNAAM, COUNT(*) AS locks,
       STRING_AGG(NAAM, ', ') AS lock_names
FROM read_parquet('https://data.source.coop/cholmes/portolan-nl/rijkswaterstaat/sluizen/sluizen.parquet')
GROUP BY VRTNAAM
ORDER BY locks DESC
```

### Find locks near a location (within 10 km)

```sql
INSTALL spatial; LOAD spatial;

SELECT NAAM, PLAATSNAAM, VRTNAAM,
       ST_Distance(ST_GeomFromWKB(geometry),
           ST_Transform(ST_Point(5.69, 51.44), 'EPSG:4326', 'EPSG:28992')
       ) / 1000 AS distance_km
FROM read_parquet('https://data.source.coop/cholmes/portolan-nl/rijkswaterstaat/sluizen/sluizen.parquet')
WHERE distance_km < 10
ORDER BY distance_km
```

## Geometry Notes

- CRS is **EPSG:28992** (Amersfoort / RD New). Coordinates are in metres.
- All geometries are Point — representing lock locations, not the full lock structure.
- Reproject to EPSG:4326 for web maps.


## Visualization Styles

One Mapbox GL v8 style is available for interactive map visualization via the PMTiles file.

Style files are Mapbox GL v8 JSON with relative PMTiles source paths. They can be
used with MapLibre GL JS, OpenLayers (via ol-mapbox-style), or any Mapbox GL v8-compatible renderer.

- **`styles/default.json`** — Red circles sized by `NR_KOLKEN` (number of lock chambers). Larger circles = more chambers = higher-capacity locks. Labels show lock names at higher zoom.

Style files are at: `https://data.source.coop/cholmes/portolan-nl/rijkswaterstaat/sluizen/styles/`
## Caveats

- Column names use uppercase (e.g., `NAAM`, `PLAATSNAAM`, `NR_KOLKEN`).
- This covers the **recreational waterway network** — not all locks in the Netherlands.
- `NR_KOLKEN` may be stored as float due to null handling; cast to int for display.
- Phone numbers (`TEL_NR`) may be outdated.