Graham McIntire
e3d430f8c4
Show on /weather where the detected duct geometry traps each microwave band. Overview mode bins cells by their lowest trapped frequency (Bean & Dutton cutoff); band-picker mode masks cells whose duct doesn't reach the selected band. Cutoff is pre-computed per cell in both writers (Elixir derive + Rust derive_row reads best_duct_freq_ghz from CellValues), persisted to ScalarFile, and shipped to the JS hook via the existing binary cell pack. Also cleans up six pre-existing length/1 credo warnings in unrelated test files.
99 lines
4.4 KiB
Markdown
99 lines
4.4 KiB
Markdown
# Duct Cutoff Weather Layer
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Add a `/weather` overlay that colours each grid cell by the lowest microwave-band frequency that its currently-detected duct(s) can trap. Operators can see at a glance where the duct geometry is strong enough to support 10 / 24 / 47 / 76 / 122 / 241 GHz operation.
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Physics: the Bean & Dutton waveguide approximation
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`f_min = c / (2.5·d·√(ΔM·1e-6))` is already implemented in
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both `Microwaveprop.Propagation.Duct.min_trapped_frequency_ghz/1`
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(Elixir) and `prop_grid_rs::duct::min_trapped_frequency_ghz` (Rust).
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Per-duct `min_freq_ghz` is already pre-computed at HRRR ingestion.
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## What ships
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A new map layer in the existing `/weather` picker, group `"Ducting"`,
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id `"duct_cutoff_ghz"`. Two render modes inside one layer:
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- **Overview**: continuous bin colouring keyed on canonical microwave
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bands (3.4 / 5.7 / 10 / 24 / 47 / 76 / 122 / 241 GHz). Cells with no
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duct render transparent.
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- **Band picker**: user selects one band; cells where
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`cutoff_ghz ≤ band` get a single solid fill, else transparent.
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Click readout: `"Best duct cutoff: 18.4 GHz · 2 ducts · thickest 84 m"`.
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## Data plumbing
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Per cell we want a single scalar `duct_cutoff_ghz` = min cutoff across
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all detected ducts. Both writers must emit it; the wire format is
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unchanged otherwise.
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**Elixir derive path** (`Microwaveprop.Weather.WeatherLayers.derive/1`):
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Iterate `row.duct_characteristics`. Read `min_freq_ghz` (atom or string)
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from each entry; fall back to `Duct.min_trapped_frequency_ghz/1` if
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only `thickness_m` + `m_deficit` are present; skip sounding-shape
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entries that have neither. Take the minimum, return `nil` if none.
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**Rust derive path** (`prop_grid_rs::weather_scalar_file::derive_row`):
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Add `duct_cutoff_ghz: Option<f64>` to `ScalarRow`. Read `cell.get
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("best_duct_freq_ghz")` — `native_duct::reduce_grid_to_ducts` already
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stashes it. No new computation needed.
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**ScalarFile @atom_keys**: add `"duct_cutoff_ghz"` so Elixir reads
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deserialise into the atom-keyed shape that callers expect.
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**WeatherTileController @cell_fields**: add `:duct_cutoff_ghz` to the
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binary cell-pack whitelist. The pack format itself doesn't need
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changes — it's already a generic per-field f32 array list.
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**MapLayers**: register the new entry alongside `duct_strength`.
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## UI
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`WeatherMapLive` gets one extra assign, `:band_filter` (default `nil` =
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overview mode, otherwise an integer GHz value from the band buttons).
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When the selected layer is `"duct_cutoff_ghz"`, render an inline strip
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of band buttons (`[All] [10] [24] [47] [76] [122] [241]`) below the
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layer picker. Clicking a band sends `select_band_filter`, which updates
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the assign and pushes `set_band_filter` to the JS hook. Clicking the
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active band again resets to `nil`. The band filter state lives in
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URL params (`?band=24`) so deep links work.
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JS hook (`WeatherMap`): add a colour mapper branch keyed on layer id
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`"duct_cutoff_ghz"`. In overview mode, bin the value through the
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canonical band thresholds; in band-picker mode, render a single fill
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colour where `value ≤ selected_band` (NaN → transparent). The
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existing point-detail readout uses the same value field.
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## Edge cases
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- Old ScalarFiles without `duct_cutoff_ghz`: field decodes to `nil` →
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NaN on the wire → transparent. Resolves naturally as new hourly
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scalar files are written.
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- Cells with no ducts: `duct_cutoff_ghz: nil` → transparent (correct).
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- Sounding-shape ducts (`%{"base", "strength"}` without
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thickness/M-deficit): skipped in the Elixir derive. They don't
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appear on a gridded HRRR map.
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- Cutoff above the highest band (e.g. 800 GHz duct only): still binned
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to the top band (≥ 241 GHz) so it doesn't fall off the colour scale.
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## Test plan
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**Elixir**:
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- `WeatherLayersTest` — `derive/1` with a native-duct row returns the
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min `min_freq_ghz`; with no ducts returns `nil`; with mixed
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shapes prefers the computable one.
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- `WeatherTileControllerTest` — binary pack includes the new field
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when requested via `?layers=duct_cutoff_ghz`.
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- `MapLayersTest` — `valid_id?/1` accepts `"duct_cutoff_ghz"`.
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**Rust**:
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- `weather_scalar_file::derive_row` test passes a `CellValues` with
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`best_duct_freq_ghz: 18.4` and asserts the field round-trips.
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**LiveView**:
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- `WeatherMapLiveTest` — selecting the new layer renders the band
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buttons; clicking 24 updates the assign and pushes the event.
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Out of scope for v1: HRDPS band cutoff layer (same plumbing applies,
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add later), historical backfill of the new field into old
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ScalarFiles (let hourly writes refresh).
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