# Quickstart - from scratch

The Quickstart chapter walks you through the example project. This chapter shows the same workflow but starting with a blank QGIS project: how to draw your first leg, set its width, bring in depth and object data, and produce a first risk number.

## 1. Open the plugin (no project loaded)

Open QGIS, click the OMRAT icon, and dock the panel on the right. With nothing loaded the Routes tab looks like this:

Routes tab on a fresh project. `twRouteList` is empty and the distribution panel below shows zeroed defaults.

The QGIS canvas before any layer is added. Most users begin by adding a basemap (XYZ Tiles → OpenStreetMap is fine).

## 2. Place legs on the map

A leg is a single straight segment of a route. OMRAT calculates risk per leg, so a curved or branching route is approximated with several short legs joined end to end.

To draw a leg:

1. Click Place leg on the Routes tab toolbar. The cursor turns into a crosshair.

2. Click the start point on the canvas.

3. Click the end point. The leg is added to `twRouteList` and a blue line appears on the canvas.

4. Repeat for each leg. Click Stop route to leave place-leg mode.

After one leg the Routes tab shows the new row:

The first leg appears in `twRouteList` (Segment 1, Route 1). Adjust Width to the half-width of the corridor in metres (5000 = a 5 km wide corridor).

The leg as drawn on the canvas. Two grey “offset” lines mark the width of the corridor.

Tip

Endpoints that exactly coincide between legs (within metres, not visually) are treated as shared vertices: dragging one with the QGIS Vertex Tool moves every connected leg’s endpoint together, so a curved route stays connected when you re-route.

## 3. Bring in depth data

Powered grounding and drifting grounding both rely on a depth contour layer. OMRAT consumes depth polygons (one per discrete depth value).

Where to get depth data:

- EMODnet Bathymetry (https://emodnet.ec.europa.eu/en/bathymetry) - free 1/16 arc-min DTM for European seas. Download a tile, contour it in QGIS (Raster → Extraction → Contour Polygons), then load the resulting polygons into the Depths tab.

- GEBCO (https://www.gebco.net/) - global 15-arc-second bathymetry. Same workflow.

- Local hydrographic offices - national bathymetry products are usually higher resolution but require a license.

- ENCs (Electronic Navigational Charts) - if you have access to S-57/S-101 chart data, the Depth Areas (DEPARE) layer is exactly what OMRAT wants.

Once you have polygons in QGIS, switch to the Depths tab and use Add depth from layer to import them. The tab is empty before any depths are added:

Depths tab on a fresh project. Each row links one polygon to its depth value (in metres, positive downwards).

## 4. Define obstacles (objects)

Bridges, wind-park footprints, and other surface structures go on the Objects tab. The workflow is identical to Depths: import a polygon layer (or digitise polygons by hand) and set the structure’s height in metres above sea level.

Objects tab on a fresh project. Powered allision and drifting allision use the polygons listed here.

Common sources for object polygons:

- OpenStreetMap - bridges, piers and offshore wind farms tagged `man_made=*` are usually present.

- EMODnet Human Activities - offshore platforms, wind-farm layouts.

- National marine spatial planning portals.

## 5. Settings: drift, ship categories, causation, AIS

Open the relevant Settings dialog from the dock’s gear menu.

Drift Settings. The wind-rose drives drifting risk – start from a uniform 1/8 distribution if you don’t yet have site-specific data, then refine using a local meteorological reanalysis (ERA5, MERRA-2).

The other Settings dialogs are documented in User Guide:

- Ship Categories - the type/size matrix that maps AIS rows to the cells of the traffic table.

- Causation Factors - the per-accident-type Pc values.

- AIS Connection - host/database/user for the optional AIS Postgres database. If you don’t have an AIS database, fill the traffic table in by hand on the Traffic tab.

## 6. Run the model

Switch to the Run Analysis tab, fill in:

- Name of the model - a short slug for this scenario.

- File path - a folder. Each Run writes three files into this folder:

  - `<name>_<timestamp>.gpkg` - the result layers.

  - `<name>_<timestamp>.omrat` - a snapshot of the inputs (read-only).

  - `<name>_results_<timestamp>.md` - a Markdown report covering every accident type.

Click Run Model. The Run button is greyed out until both fields are set, and a popup spells out which is missing if you click anyway.

When the run finishes the Accident probabilities table populates with one row per accident type and a View button per row that opens the matching driver visualisation.

## 7. Inspect the results

The Previous runs table at the top of the Run Analysis tab keeps every run. Select a row and click Add selected run results to map to load that run’s GeoPackage as styled QGIS layers. Two runs can be compared side-by-side from the Compare tab.

See also

- Quickstart – same flow, but with the example project.

- User Guide – detailed reference for every tab.

- Concepts – glossary of the OMRAT-specific vocabulary.