Requirements:
- A shape file of the 'sub-areas' of the hotspot
- A shape file of the receptor
- A text file with information on the grid as it is in FEWS. The first two columns contain all coordinates. The third column contains a unique gridID which can be used to access the right coordinates in the hazard.nc. Ordering is important.
All three files need to be in the same projection.
Creating the FEWS_grid.txt
See first part of this Matlab code as example.
Step-by-step tutorial for QGIS: Creating the <receptor>.txt in QGIS
Open a new project in QGIS
Add the FEWSGrid.txt as an delimited text layer to a empty project (Layer -> Add Layer -> Add Delimited Text Layer). In the popup window select 'First record has field names', e.g.:
Add the shape files (Layer -> Add Layer -> Add Vector Layer). After this the screen should look like this:
- Introduce unique IDs for each sub-area (or "sector") and each receptor
- Select a layer and open its attribute table (Right click -> Open attribute table)
- 'Toggle editing mode' (pencil icon)
- 'Open field calculator'
- Check the 'Create a new field' box and choose an 'output field name' (receptorID or areaID depending on the layer you selected)
- Set 'Expression' to $rownum
- Click 'Ok'
- 'Save edits' and once more 'Toggle editing mode'
- Repeat a-d for the other layer
- Intersect the receptor layer with the area layer (Vector -> Geoprocessing Tools -> Intersect) and save the new layer under a new name (in this example ResBuildings_hotspot.shp)
The resulting layer will contain all the buildings within the hotspot and associate them with the areaID of the area there in. - Create a new polygon shape file from the FEWSGrid layer (Vector -> Geometry tools -> Voronoi Polygons) and save under a new name (in this example FEWSGrid_polygon.shp).
- Intersect this FEWSGrid_polygon layer with the ResBuildings_hotspot layer. (Vector -> Geoprocessing Tools -> Intersect) and save under new name (e.g. ResBuilding_for_BN). Each polygon in the resulting shape layer is associated with a unique combination of gridID, areaID and receptorID. This information is used by the BN Adaptor to understand in which area a receptor is located and which model grid points should be used to calculated its hazard from the hazard.nc. The resulting layer should look similar to this:
- Save the columns areaID, receptorID and gridID (in this order!!) to a <receptor>.txt file and verify that the values in receptorID are in ascending order.
- Right click on ResBuilding_for_BN -> Open Attribute Table
- 'Toggle editing mode'
- 'Delete column': all except areaID, receptorID and gridID
- 'Save edits', again 'Toggle editing mode' and close attribute table
- Save layer as Comma Separated File (Right click on ResBuilding_for_BN -> Save As e.g. 'ResBuildings.csv')
- Open ResBuildings.csv in Matlab for testing
- Save as <receptor>.txt file