Units Conversions

[gassc]

We need to track unit conversions from start to finish. Original equations presume that input data had certain area/length units, and consequently had some hard-coded conversions within.

We can auto-derive units from inputs with Python-Pint. Doing so from the flow direction raster is most appropriate since the spatial properties like area and length are being derived from derivatives of that input; it's possible to detect from others as needed (e.g., Curve Number Raster)

• units for length from Flow Length raster: used in the T/C calculation (what units for flow length does T/C assume?)
  • https://github.com/civicmapper/peak-flow-calculator/blob/3e593e2c95573303200ea01da2aa94124b18d9e3/core/logic/gp.py#L341
  • https://github.com/civicmapper/peak-flow-calculator/blob/3e593e2c95573303200ea01da2aa94124b18d9e3/core/logic/calc.py#L17
• storage units: used in the peak flow calculation, one input assumes area unit of Curve Number raster
  • https://github.com/civicmapper/peak-flow-calculator/blob/3e593e2c95573303200ea01da2aa94124b18d9e3/core/logic/calc.py#L81
• area units for catchments: used in peak flow calculation. Square Kilometers

[gassc]

confirmed units. Implemented unit detection for flow length