ASA: Topographic Position Index statistics

**As a** person issuing or receiving fire behaviour advisories

**I need** general information on what elevations advisory conditions are expected

**So That** I have better topographic context, i.e.) valley bottom, mid-slope, ridge top.

**Acceptance Criteria**
- [ ] Given advisory conditions are present in a fire zone unit, When I select a fire zone unit on the map, Then the elevation statics shown in the left side panel provide the proportion of advisory cells in valley bottom, mid-slope, and ridge top.
- [ ] All HFI values >= 4,000 kW/m can be used to create a single bar chart for the three topographic classes similar to the Combustible Land Under Advisory or Warning chart.
- [ ] Remove min/max elevation statistics table.

**Additional Context**
- Classified Topographic Position Index (TPI) grid to be created ahead of time before this story can be actioned.
- Could consider using surface roughness grid to define the size of the moving window used for the TPI calculation.
- Resolution of the TPI grid needs to match the SFMS outputs (2000 m).

TPI - https://blogs.ubc.ca/tdeenik/2021/02/16/topographic-position-index-tpi/

**Definition of Done**
https://github.com/bcgov/wps/wiki/Definition-of-Done

Start by locating the existing Combustible Land Under Advisory or Warning chart and the left-side fire zone unit statistics panel. Confirm that the classified TPI grid prerequisite exists at the 2000 m SFMS resolution, then trace how advisory cells and HFI values are supplied. Done means showing the three topographic proportions, charting HFI values >= 4,000 kW/m, and removing the min/max elevation table.

Written by the indexing model from the issue text.