diff --git a/lib/microwaveprop/geo.ex b/lib/microwaveprop/geo.ex
index b153fbf6..df20d854 100644
--- a/lib/microwaveprop/geo.ex
+++ b/lib/microwaveprop/geo.ex
@@ -10,12 +10,17 @@ defmodule Microwaveprop.Geo do
   def haversine_km(lat1, lon1, lat2, lon2) do
     dlat = deg_to_rad(lat2 - lat1)
     dlon = deg_to_rad(lon2 - lon1)
+    rlat1 = deg_to_rad(lat1)
+    rlat2 = deg_to_rad(lat2)
 
     a =
       :math.sin(dlat / 2) ** 2 +
-        :math.cos(deg_to_rad(lat1)) * :math.cos(deg_to_rad(lat2)) * :math.sin(dlon / 2) ** 2
+        :math.cos(rlat1) * :math.cos(rlat2) * :math.sin(dlon / 2) ** 2
 
-    2 * @earth_radius_km * :math.asin(:math.sqrt(a))
+    # `atan2(√a, √(1−a))` is the numerically stable form: when `a`
+    # rounds to slightly above 1 the asin form returns NaN, while
+    # atan2 stays finite.
+    2 * @earth_radius_km * :math.atan2(:math.sqrt(a), :math.sqrt(1 - a))
   end
 
   @doc "Initial bearing from point 1 to point 2 in degrees (0-360)."
diff --git a/lib/microwaveprop/ionosphere.ex b/lib/microwaveprop/ionosphere.ex
index 6bc8dedd..9939a406 100644
--- a/lib/microwaveprop/ionosphere.ex
+++ b/lib/microwaveprop/ionosphere.ex
@@ -99,21 +99,5 @@ defmodule Microwaveprop.Ionosphere do
     Enum.min_by(@stations, fn s -> haversine_km(lat, lon, s.lat, s.lon) end)
   end
 
-  # Standard haversine distance in km. Good enough for station-pick
-  # ranking — we're not computing hop geometry here.
-  defp haversine_km(lat1, lon1, lat2, lon2) do
-    r = 6371.0
-    dlat = :math.pi() * (lat2 - lat1) / 180
-    dlon = :math.pi() * (lon2 - lon1) / 180
-    lat1_rad = :math.pi() * lat1 / 180
-    lat2_rad = :math.pi() * lat2 / 180
-
-    a =
-      :math.sin(dlat / 2) * :math.sin(dlat / 2) +
-        :math.cos(lat1_rad) * :math.cos(lat2_rad) *
-          :math.sin(dlon / 2) * :math.sin(dlon / 2)
-
-    c = 2 * :math.atan2(:math.sqrt(a), :math.sqrt(1 - a))
-    r * c
-  end
+  defp haversine_km(lat1, lon1, lat2, lon2), do: Microwaveprop.Geo.haversine_km(lat1, lon1, lat2, lon2)
 end
diff --git a/lib/microwaveprop/propagation/band_config.ex b/lib/microwaveprop/propagation/band_config.ex
index b74204c7..545d21ee 100644
--- a/lib/microwaveprop/propagation/band_config.ex
+++ b/lib/microwaveprop/propagation/band_config.ex
@@ -855,6 +855,17 @@ defmodule Microwaveprop.Propagation.BandConfig do
     Enum.map(all_bands(), fn band -> {band.label, to_string(band.freq_mhz)} end)
   end
 
+  @doc """
+  Human-readable label for a band's `:humidity_effect`. Accepts the
+  band config map or any map with a `:humidity_effect` key; falls back
+  to `"neutral"` for missing/unrecognized values so templates can
+  render unconditionally.
+  """
+  @spec humidity_effect_label(map() | nil) :: String.t()
+  def humidity_effect_label(%{humidity_effect: :beneficial}), do: "beneficial"
+  def humidity_effect_label(%{humidity_effect: :harmful}), do: "harmful"
+  def humidity_effect_label(_), do: "neutral"
+
   @doc "Returns the default scoring weights map. All 10 values sum to 1.0."
   @spec weights() :: map()
   def weights, do: @weights
diff --git a/lib/microwaveprop/propagation/common_volume.ex b/lib/microwaveprop/propagation/common_volume.ex
index 006a6d37..599e6336 100644
--- a/lib/microwaveprop/propagation/common_volume.ex
+++ b/lib/microwaveprop/propagation/common_volume.ex
@@ -14,7 +14,6 @@ defmodule Microwaveprop.Propagation.CommonVolume do
   Distances are spherical-great-circle (haversine) at mean Earth radius.
   """
 
-  @earth_radius_km 6371.0
   @km_per_deg_lat 111.32
 
   @type latlon :: {float(), float()}
@@ -78,20 +77,5 @@ defmodule Microwaveprop.Propagation.CommonVolume do
     end
   end
 
-  @doc "Great-circle distance (km) between two lat/lon points."
-  @spec haversine_km(latlon(), latlon()) :: float()
-  def haversine_km({lat1, lon1}, {lat2, lon2}) do
-    rlat1 = lat1 * :math.pi() / 180.0
-    rlat2 = lat2 * :math.pi() / 180.0
-    dlat = (lat2 - lat1) * :math.pi() / 180.0
-    dlon = (lon2 - lon1) * :math.pi() / 180.0
-
-    a =
-      :math.sin(dlat / 2) * :math.sin(dlat / 2) +
-        :math.cos(rlat1) * :math.cos(rlat2) *
-          :math.sin(dlon / 2) * :math.sin(dlon / 2)
-
-    c = 2.0 * :math.atan2(:math.sqrt(a), :math.sqrt(1.0 - a))
-    @earth_radius_km * c
-  end
+  defp haversine_km({lat1, lon1}, {lat2, lon2}), do: Microwaveprop.Geo.haversine_km(lat1, lon1, lat2, lon2)
 end
diff --git a/lib/microwaveprop/propagation/rain_scatter.ex b/lib/microwaveprop/propagation/rain_scatter.ex
index 9d31f836..bb4c1195 100644
--- a/lib/microwaveprop/propagation/rain_scatter.ex
+++ b/lib/microwaveprop/propagation/rain_scatter.ex
@@ -15,8 +15,6 @@ defmodule Microwaveprop.Propagation.RainScatter do
   volume, and R1/R2 are distances from each endpoint to the cell.
   """
 
-  @earth_radius_km 6371.0
-
   # Minimum reflectivity to consider for scatter (dBZ)
   @min_dbz 25.0
 
@@ -132,20 +130,7 @@ defmodule Microwaveprop.Propagation.RainScatter do
     baseline + z_term + freq_factor - range_loss + volume_term
   end
 
-  defp haversine_km(lat1, lon1, lat2, lon2) do
-    dlat = :math.pi() * (lat2 - lat1) / 180.0
-    dlon = :math.pi() * (lon2 - lon1) / 180.0
-    rlat1 = :math.pi() * lat1 / 180.0
-    rlat2 = :math.pi() * lat2 / 180.0
-
-    a =
-      :math.sin(dlat / 2) * :math.sin(dlat / 2) +
-        :math.cos(rlat1) * :math.cos(rlat2) *
-          :math.sin(dlon / 2) * :math.sin(dlon / 2)
-
-    c = 2.0 * :math.atan2(:math.sqrt(a), :math.sqrt(1.0 - a))
-    @earth_radius_km * c
-  end
+  defp haversine_km(lat1, lon1, lat2, lon2), do: Microwaveprop.Geo.haversine_km(lat1, lon1, lat2, lon2)
 
   defp bearing_deg(lat1, lon1, lat2, lon2) do
     rlat1 = :math.pi() * lat1 / 180.0
diff --git a/lib/microwaveprop/propagation/scorer.ex b/lib/microwaveprop/propagation/scorer.ex
index ed4dda0c..2979132f 100644
--- a/lib/microwaveprop/propagation/scorer.ex
+++ b/lib/microwaveprop/propagation/scorer.ex
@@ -95,17 +95,15 @@ defmodule Microwaveprop.Propagation.Scorer do
   end
 
   def score_humidity(abs_humidity, %{humidity_effect: :harmful, humidity_penalty: penalty}) do
-    r = abs_humidity * penalty
-
-    cond do
-      r <= 6 -> 100
-      r <= 9 -> round(95 - (r - 6) / 3 * 20)
-      r <= 13 -> round(75 - (r - 9) / 4 * 30)
-      r <= 18 -> round(45 - (r - 13) / 5 * 35)
-      true -> max(0, round(10 - (r - 18) * 2))
-    end
+    score_humidity_harmful(abs_humidity * penalty)
   end
 
+  defp score_humidity_harmful(r) when r <= 6, do: 100
+  defp score_humidity_harmful(r) when r <= 9, do: round(95 - (r - 6) / 3 * 20)
+  defp score_humidity_harmful(r) when r <= 13, do: round(75 - (r - 9) / 4 * 30)
+  defp score_humidity_harmful(r) when r <= 18, do: round(45 - (r - 13) / 5 * 35)
+  defp score_humidity_harmful(r), do: max(0, round(10 - (r - 18) * 2))
+
   # ── Factor 2: Time of day ─────────────────────────────────────────
 
   @doc """
@@ -150,29 +148,25 @@ defmodule Microwaveprop.Propagation.Scorer do
   """
   @spec score_td_depression(number(), number(), map()) :: integer()
   def score_td_depression(temp_f, dewpoint_f, %{humidity_effect: :beneficial}) do
-    dep = temp_f - dewpoint_f
-
-    cond do
-      dep < 3 -> 40
-      dep < 8 -> 75
-      dep < 14 -> 85
-      dep < 22 -> 70
-      true -> 55
-    end
+    score_td_beneficial(temp_f - dewpoint_f)
   end
 
   def score_td_depression(temp_f, dewpoint_f, %{humidity_effect: :harmful}) do
-    dep = temp_f - dewpoint_f
-
-    cond do
-      dep > 22 -> 96
-      dep > 14 -> 80
-      dep > 8 -> 60
-      dep > 4 -> 38
-      true -> 18
-    end
+    score_td_harmful(temp_f - dewpoint_f)
   end
 
+  defp score_td_beneficial(dep) when dep < 3, do: 40
+  defp score_td_beneficial(dep) when dep < 8, do: 75
+  defp score_td_beneficial(dep) when dep < 14, do: 85
+  defp score_td_beneficial(dep) when dep < 22, do: 70
+  defp score_td_beneficial(_dep), do: 55
+
+  defp score_td_harmful(dep) when dep > 22, do: 96
+  defp score_td_harmful(dep) when dep > 14, do: 80
+  defp score_td_harmful(dep) when dep > 8, do: 60
+  defp score_td_harmful(dep) when dep > 4, do: 38
+  defp score_td_harmful(_dep), do: 18
+
   # ── Factor 4: Refractivity ───────────────────────────────────────
 
   @doc """
@@ -302,16 +296,11 @@ defmodule Microwaveprop.Propagation.Scorer do
   @doc "Scores sky cover percentage (0 = clear, 100 = overcast). Nil returns 50."
   @spec score_sky(number() | nil) :: integer()
   def score_sky(nil), do: 50
-
-  def score_sky(pct) do
-    cond do
-      pct <= 6 -> 100
-      pct <= 25 -> 88
-      pct <= 50 -> 60
-      pct <= 87 -> 25
-      true -> 5
-    end
-  end
+  def score_sky(pct) when pct <= 6, do: 100
+  def score_sky(pct) when pct <= 25, do: 88
+  def score_sky(pct) when pct <= 50, do: 60
+  def score_sky(pct) when pct <= 87, do: 25
+  def score_sky(_pct), do: 5
 
   # ── Factor 6: Season ─────────────────────────────────────────────
 
@@ -345,17 +334,12 @@ defmodule Microwaveprop.Propagation.Scorer do
   @doc "Scores wind speed in knots. Nil returns 50."
   @spec score_wind(number() | nil) :: integer()
   def score_wind(nil), do: 50
-
-  def score_wind(speed_kts) do
-    cond do
-      speed_kts < 5 -> 100
-      speed_kts < 10 -> 90
-      speed_kts < 15 -> 75
-      speed_kts < 20 -> 55
-      speed_kts < 25 -> 35
-      true -> 15
-    end
-  end
+  def score_wind(speed_kts) when speed_kts < 5, do: 100
+  def score_wind(speed_kts) when speed_kts < 10, do: 90
+  def score_wind(speed_kts) when speed_kts < 15, do: 75
+  def score_wind(speed_kts) when speed_kts < 20, do: 55
+  def score_wind(speed_kts) when speed_kts < 25, do: 35
+  def score_wind(_speed_kts), do: 15
 
   # ── Factor 8: Rain attenuation ───────────────────────────────────
 
@@ -369,18 +353,16 @@ defmodule Microwaveprop.Propagation.Scorer do
   def score_rain(rate, _band_config) when rate == 0, do: 100
 
   def score_rain(rain_rate_mmhr, %{rain_k: k, rain_alpha: alpha}) do
-    gamma = k * :math.pow(rain_rate_mmhr, alpha)
-
-    cond do
-      gamma < 0.1 -> 95
-      gamma < 0.5 -> 75
-      gamma < 1.0 -> 50
-      gamma < 2.0 -> 25
-      gamma < 5.0 -> 10
-      true -> 0
-    end
+    score_rain_gamma(k * :math.pow(rain_rate_mmhr, alpha))
   end
 
+  defp score_rain_gamma(gamma) when gamma < 0.1, do: 95
+  defp score_rain_gamma(gamma) when gamma < 0.5, do: 75
+  defp score_rain_gamma(gamma) when gamma < 1.0, do: 50
+  defp score_rain_gamma(gamma) when gamma < 2.0, do: 25
+  defp score_rain_gamma(gamma) when gamma < 5.0, do: 10
+  defp score_rain_gamma(_gamma), do: 0
+
   # ── Factor 9: Precipitable water ──────────────────────────────────
 
   @doc """
@@ -392,25 +374,20 @@ defmodule Microwaveprop.Propagation.Scorer do
   @spec score_pwat(number() | nil, map()) :: integer()
   def score_pwat(nil, _band_config), do: 60
 
-  def score_pwat(pwat_mm, %{humidity_effect: :beneficial}) do
-    cond do
-      pwat_mm < 10 -> 55
-      pwat_mm < 20 -> 75
-      pwat_mm < 30 -> 90
-      pwat_mm < 40 -> 70
-      true -> 50
-    end
-  end
+  def score_pwat(pwat_mm, %{humidity_effect: :beneficial}), do: score_pwat_beneficial(pwat_mm)
+  def score_pwat(pwat_mm, %{humidity_effect: :harmful}), do: score_pwat_harmful(pwat_mm)
 
-  def score_pwat(pwat_mm, %{humidity_effect: :harmful}) do
-    cond do
-      pwat_mm < 10 -> 95
-      pwat_mm < 20 -> 80
-      pwat_mm < 30 -> 60
-      pwat_mm < 40 -> 35
-      true -> 15
-    end
-  end
+  defp score_pwat_beneficial(pwat) when pwat < 10, do: 55
+  defp score_pwat_beneficial(pwat) when pwat < 20, do: 75
+  defp score_pwat_beneficial(pwat) when pwat < 30, do: 90
+  defp score_pwat_beneficial(pwat) when pwat < 40, do: 70
+  defp score_pwat_beneficial(_pwat), do: 50
+
+  defp score_pwat_harmful(pwat) when pwat < 10, do: 95
+  defp score_pwat_harmful(pwat) when pwat < 20, do: 80
+  defp score_pwat_harmful(pwat) when pwat < 30, do: 60
+  defp score_pwat_harmful(pwat) when pwat < 40, do: 35
+  defp score_pwat_harmful(_pwat), do: 15
 
   # ── Factor 10: Pressure trend ────────────────────────────────────
 
@@ -422,29 +399,21 @@ defmodule Microwaveprop.Propagation.Scorer do
   """
   @spec score_pressure(number() | nil, number() | nil) :: integer()
   def score_pressure(nil, _previous_mb), do: 50
+  def score_pressure(current_mb, nil), do: score_pressure_absolute(current_mb)
+  def score_pressure(current_mb, previous_mb), do: score_pressure_delta(current_mb - previous_mb)
 
-  def score_pressure(current_mb, nil) do
-    cond do
-      current_mb < 980 -> 88
-      current_mb < 990 -> 82
-      current_mb < 1000 -> 70
-      current_mb < 1010 -> 55
-      current_mb < 1020 -> 40
-      true -> 30
-    end
-  end
+  defp score_pressure_absolute(mb) when mb < 980, do: 88
+  defp score_pressure_absolute(mb) when mb < 990, do: 82
+  defp score_pressure_absolute(mb) when mb < 1000, do: 70
+  defp score_pressure_absolute(mb) when mb < 1010, do: 55
+  defp score_pressure_absolute(mb) when mb < 1020, do: 40
+  defp score_pressure_absolute(_mb), do: 30
 
-  def score_pressure(current_mb, previous_mb) do
-    delta = current_mb - previous_mb
-
-    cond do
-      delta > 2.5 -> 80
-      delta > 0.8 -> 70
-      delta > -0.5 -> 60
-      delta > -2.0 -> 65
-      true -> 45
-    end
-  end
+  defp score_pressure_delta(delta) when delta > 2.5, do: 80
+  defp score_pressure_delta(delta) when delta > 0.8, do: 70
+  defp score_pressure_delta(delta) when delta > -0.5, do: 60
+  defp score_pressure_delta(delta) when delta > -2.0, do: 65
+  defp score_pressure_delta(_delta), do: 45
 
   # ── Composite score ──────────────────────────────────────────────
 
@@ -541,26 +510,33 @@ defmodule Microwaveprop.Propagation.Scorer do
     build_path_conditions(extracted, contact)
   end
 
+  @path_fields [
+    {:temps, :surface_temp_c},
+    {:dewpoints, :surface_dewpoint_c},
+    {:pressures, :surface_pressure_mb},
+    {:gradients, :min_refractivity_gradient},
+    {:bl_depths, :hpbl_m},
+    {:pwats, :pwat_mm}
+  ]
+
   defp extract_profile_fields(profiles) do
-    Enum.reduce(profiles, {[], [], [], [], [], []}, fn p, {t, d, pr, g, b, pw} ->
-      {
-        if(is_nil(p.surface_temp_c), do: t, else: [p.surface_temp_c | t]),
-        if(is_nil(p.surface_dewpoint_c), do: d, else: [p.surface_dewpoint_c | d]),
-        if(is_nil(p.surface_pressure_mb), do: pr, else: [p.surface_pressure_mb | pr]),
-        if(is_nil(p.min_refractivity_gradient), do: g, else: [p.min_refractivity_gradient | g]),
-        if(is_nil(p.hpbl_m), do: b, else: [p.hpbl_m | b]),
-        if(is_nil(p.pwat_mm), do: pw, else: [p.pwat_mm | pw])
-      }
+    empty = Map.new(@path_fields, fn {bucket, _} -> {bucket, []} end)
+    Enum.reduce(profiles, empty, &accumulate_profile/2)
+  end
+
+  defp accumulate_profile(profile, acc) do
+    Enum.reduce(@path_fields, acc, fn {bucket, key}, acc ->
+      maybe_prepend(acc, bucket, Map.get(profile, key))
     end)
   end
 
-  defp build_path_conditions({temps, _dewpoints, _pressures, _gradients, _bl_depths, _pwats}, _contact) when temps == [],
-    do: nil
+  defp maybe_prepend(acc, _bucket, nil), do: acc
+  defp maybe_prepend(acc, bucket, value), do: Map.update!(acc, bucket, &[value | &1])
 
-  defp build_path_conditions({_temps, dewpoints, _pressures, _gradients, _bl_depths, _pwats}, _contact)
-       when dewpoints == [], do: nil
+  defp build_path_conditions(%{temps: []}, _contact), do: nil
+  defp build_path_conditions(%{dewpoints: []}, _contact), do: nil
 
-  defp build_path_conditions({temps, dewpoints, pressures, gradients, bl_depths, pwats}, contact) do
+  defp build_path_conditions(%{temps: temps, dewpoints: dewpoints} = buckets, contact) do
     lon = contact.pos1["lon"] || -97.0
     avg_temp_c = Enum.sum(temps) / length(temps)
     avg_dewpoint_c = Enum.sum(dewpoints) / length(dewpoints)
@@ -575,18 +551,15 @@ defmodule Microwaveprop.Propagation.Scorer do
       utc_minute: contact.qso_timestamp.minute,
       month: contact.qso_timestamp.month,
       longitude: lon,
-      pressure_mb: safe_min(pressures),
+      pressure_mb: Enum.min(buckets.pressures, fn -> nil end),
       prev_pressure_mb: nil,
       rain_rate_mmhr: 0.0,
-      min_refractivity_gradient: safe_min(gradients),
-      bl_depth_m: safe_avg(bl_depths),
-      pwat_mm: safe_avg(pwats)
+      min_refractivity_gradient: Enum.min(buckets.gradients, fn -> nil end),
+      bl_depth_m: safe_avg(buckets.bl_depths),
+      pwat_mm: safe_avg(buckets.pwats)
     }
   end
 
-  defp safe_min([]), do: nil
-  defp safe_min(list), do: Enum.min(list)
-
   defp safe_avg([]), do: nil
   defp safe_avg(list), do: Enum.sum(list) / length(list)
 end
diff --git a/lib/microwaveprop/propagation/scores_file.ex b/lib/microwaveprop/propagation/scores_file.ex
index 083735b8..9d5062df 100644
--- a/lib/microwaveprop/propagation/scores_file.ex
+++ b/lib/microwaveprop/propagation/scores_file.ex
@@ -444,9 +444,7 @@ defmodule Microwaveprop.Propagation.ScoresFile do
     end
   end
 
-  defp clamp(n, lo, _hi) when n < lo, do: lo
-  defp clamp(n, _lo, hi) when n > hi, do: hi
-  defp clamp(n, _lo, _hi), do: n
+  defp clamp(n, lo, hi), do: n |> max(lo) |> min(hi)
 
   defp max_datetime([]), do: nil
   defp max_datetime(times), do: Enum.max(times, DateTime)
diff --git a/lib/microwaveprop/radio.ex b/lib/microwaveprop/radio.ex
index f49fba75..01197a51 100644
--- a/lib/microwaveprop/radio.ex
+++ b/lib/microwaveprop/radio.ex
@@ -405,24 +405,8 @@ defmodule Microwaveprop.Radio do
   defp normalize_lon(lon) when lon < -180.0, do: lon + 360.0
   defp normalize_lon(lon), do: lon
 
-  @earth_radius_km 6371.0
-
   @spec haversine_km(number(), number(), number(), number()) :: float()
-  def haversine_km(lat1, lon1, lat2, lon2) do
-    dlat = deg_to_rad(lat2 - lat1)
-    dlon = deg_to_rad(lon2 - lon1)
-    rlat1 = deg_to_rad(lat1)
-    rlat2 = deg_to_rad(lat2)
-
-    a =
-      :math.sin(dlat / 2) ** 2 +
-        :math.cos(rlat1) * :math.cos(rlat2) * :math.sin(dlon / 2) ** 2
-
-    # `atan2(√a, √(1−a))` is the numerically stable form: when `a`
-    # rounds to slightly above 1 the asin form returns NaN, while
-    # atan2 stays finite.
-    2 * @earth_radius_km * :math.atan2(:math.sqrt(a), :math.sqrt(1 - a))
-  end
+  defdelegate haversine_km(lat1, lon1, lat2, lon2), to: Microwaveprop.Geo
 
   @spec backfill_distances([Contact.t()]) :: Postgrex.Result.t() | nil
   def backfill_distances(contacts) do
diff --git a/lib/microwaveprop/rover/candidate_detail.ex b/lib/microwaveprop/rover/candidate_detail.ex
index b51c62b4..b7f66a8a 100644
--- a/lib/microwaveprop/rover/candidate_detail.ex
+++ b/lib/microwaveprop/rover/candidate_detail.ex
@@ -51,7 +51,7 @@ defmodule Microwaveprop.Rover.CandidateDetail do
           profile
           |> middle_samples()
           |> Enum.map(fn pt -> pt.elev + round(max(pt.building_m, pt.canopy_m)) end)
-          |> safe_max()
+          |> Enum.max(fn -> nil end)
 
         clearance =
           if is_integer(rover_elev) and is_integer(max_obstacle),
@@ -124,7 +124,4 @@ defmodule Microwaveprop.Rover.CandidateDetail do
   defp middle_samples([]), do: []
   defp middle_samples([_]), do: []
   defp middle_samples([_ | rest]), do: Enum.drop(rest, -1)
-
-  defp safe_max([]), do: nil
-  defp safe_max(xs), do: Enum.max(xs)
 end
diff --git a/lib/microwaveprop/rover/path_terrain.ex b/lib/microwaveprop/rover/path_terrain.ex
index 9a618261..50e6df77 100644
--- a/lib/microwaveprop/rover/path_terrain.ex
+++ b/lib/microwaveprop/rover/path_terrain.ex
@@ -67,7 +67,7 @@ defmodule Microwaveprop.Rover.PathTerrain do
           |> intermediate_samples(station_pt)
           |> Enum.map(&obstacle_top(&1, elev, buildings_lookup, canopy_lookup))
           |> Enum.reject(&is_nil/1)
-          |> safe_max()
+          |> Enum.max(fn -> nil end)
 
         if path_max, do: rover_elev - path_max
     end
@@ -101,7 +101,4 @@ defmodule Microwaveprop.Rover.PathTerrain do
       {lat1 + f * (lat2 - lat1), lon1 + f * (lon2 - lon1)}
     end
   end
-
-  defp safe_max([]), do: nil
-  defp safe_max(xs), do: Enum.max(xs)
 end
diff --git a/lib/microwaveprop/terrain/elevation_client.ex b/lib/microwaveprop/terrain/elevation_client.ex
index 018cd58a..04b27996 100644
--- a/lib/microwaveprop/terrain/elevation_client.ex
+++ b/lib/microwaveprop/terrain/elevation_client.ex
@@ -109,20 +109,7 @@ defmodule Microwaveprop.Terrain.ElevationClient do
     end
   end
 
-  defp haversine_km(lat1, lon1, lat2, lon2) do
-    dlat = deg_to_rad(lat2 - lat1)
-    dlon = deg_to_rad(lon2 - lon1)
-    rlat1 = deg_to_rad(lat1)
-    rlat2 = deg_to_rad(lat2)
-
-    a =
-      :math.sin(dlat / 2) ** 2 +
-        :math.cos(rlat1) * :math.cos(rlat2) * :math.sin(dlon / 2) ** 2
-
-    2 * 6371.0 * :math.asin(:math.sqrt(a))
-  end
-
-  defp deg_to_rad(deg), do: deg * :math.pi() / 180
+  defp haversine_km(lat1, lon1, lat2, lon2), do: Microwaveprop.Geo.haversine_km(lat1, lon1, lat2, lon2)
 
   defp req_options do
     defaults = [retry: &retry?/2, max_retries: 5, retry_delay: &retry_delay/1]
diff --git a/lib/microwaveprop/terrain/srtm.ex b/lib/microwaveprop/terrain/srtm.ex
index fc4fd518..7c696c07 100644
--- a/lib/microwaveprop/terrain/srtm.ex
+++ b/lib/microwaveprop/terrain/srtm.ex
@@ -173,18 +173,5 @@ defmodule Microwaveprop.Terrain.Srtm do
     end
   end
 
-  defp haversine_km(lat1, lon1, lat2, lon2) do
-    dlat = deg_to_rad(lat2 - lat1)
-    dlon = deg_to_rad(lon2 - lon1)
-    rlat1 = deg_to_rad(lat1)
-    rlat2 = deg_to_rad(lat2)
-
-    a =
-      :math.sin(dlat / 2) ** 2 +
-        :math.cos(rlat1) * :math.cos(rlat2) * :math.sin(dlon / 2) ** 2
-
-    2 * 6371.0 * :math.asin(:math.sqrt(a))
-  end
-
-  defp deg_to_rad(deg), do: deg * :math.pi() / 180
+  defp haversine_km(lat1, lon1, lat2, lon2), do: Microwaveprop.Geo.haversine_km(lat1, lon1, lat2, lon2)
 end
diff --git a/lib/microwaveprop/weather/weather_layers.ex b/lib/microwaveprop/weather/weather_layers.ex
index b9628cba..c224d2e8 100644
--- a/lib/microwaveprop/weather/weather_layers.ex
+++ b/lib/microwaveprop/weather/weather_layers.ex
@@ -159,19 +159,13 @@ defmodule Microwaveprop.Weather.WeatherLayers do
     ducts
     |> Enum.map(fn d -> d["base"] || d[:base_m] || d["base_m"] end)
     |> Enum.reject(&is_nil/1)
-    |> safe_min()
+    |> Enum.min(fn -> nil end)
   end
 
   defp duct_field(ducts, "strength") do
     ducts
     |> Enum.map(fn d -> d["strength"] || d[:thickness_m] || d["thickness_m"] end)
     |> Enum.reject(&is_nil/1)
-    |> safe_max()
+    |> Enum.max(fn -> nil end)
   end
-
-  defp safe_min([]), do: nil
-  defp safe_min(xs), do: Enum.min(xs)
-
-  defp safe_max([]), do: nil
-  defp safe_max(xs), do: Enum.max(xs)
 end
diff --git a/lib/microwaveprop_web/live/eme_live.ex b/lib/microwaveprop_web/live/eme_live.ex
index f9052d0c..66e284f3 100644
--- a/lib/microwaveprop_web/live/eme_live.ex
+++ b/lib/microwaveprop_web/live/eme_live.ex
@@ -18,11 +18,11 @@ defmodule MicrowavepropWeb.EmeLive do
   """
   use MicrowavepropWeb, :live_view
 
+  import MicrowavepropWeb.LiveHelpers, only: [parse_float: 2, parse_int: 2]
+
   alias Microwaveprop.Moon
   alias Microwaveprop.Propagation.BandConfig
   alias Microwaveprop.Propagation.Eme
-  alias Microwaveprop.Radio.CallsignClient
-  alias Microwaveprop.Radio.Maidenhead
 
   @band_options BandConfig.band_options()
   @tick_ms 10_000
@@ -187,87 +187,7 @@ defmodule MicrowavepropWeb.EmeLive do
 
   # --- Input parsing --------------------------------------------------
 
-  defp resolve_source(""), do: :empty
-
-  defp resolve_source(raw) do
-    input = String.trim(raw)
-
-    cond do
-      input == "" ->
-        :empty
-
-      coordinate_pair?(input) ->
-        [lat_s, lon_s] = String.split(input, ",", parts: 2)
-        {lat, _} = Float.parse(String.trim(lat_s))
-        {lon, _} = Float.parse(String.trim(lon_s))
-
-        {:ok,
-         %{
-           lat: lat,
-           lon: lon,
-           label: "#{Float.round(lat, 3)}, #{Float.round(lon, 3)}",
-           kind: :coordinates
-         }}
-
-      maidenhead?(input) ->
-        case Maidenhead.to_latlon(input) do
-          {:ok, {lat, lon}} ->
-            {:ok, %{lat: lat, lon: lon, label: String.upcase(input), kind: :grid}}
-
-          :error ->
-            {:error, "Invalid Maidenhead grid: #{input}"}
-        end
-
-      true ->
-        case CallsignClient.locate(input) do
-          {:ok, info} ->
-            {:ok,
-             %{
-               lat: info.lat,
-               lon: info.lon,
-               label: String.upcase(info.callsign),
-               grid: info.gridsquare,
-               kind: :callsign
-             }}
-
-          {:error, reason} ->
-            {:error, "Could not find #{input}: #{reason}"}
-        end
-    end
-  end
-
-  defp coordinate_pair?(input) do
-    case String.split(input, ",", parts: 2) do
-      [a, b] ->
-        match?({_, _}, Float.parse(String.trim(a))) and
-          match?({_, _}, Float.parse(String.trim(b)))
-
-      _ ->
-        false
-    end
-  end
-
-  defp maidenhead?(input) do
-    String.length(input) >= 4 and String.length(input) <= 10 and
-      Regex.match?(~r/^[A-Ra-r]{2}[0-9]{2}/i, input)
-  end
-
-  defp parse_int(s, default) do
-    case Integer.parse(to_string(s)) do
-      {n, _} -> n
-      :error -> default
-    end
-  end
-
-  defp parse_float(nil, default), do: default
-  defp parse_float("", default), do: default
-
-  defp parse_float(s, default) do
-    case Float.parse(to_string(s)) do
-      {n, _} -> n
-      :error -> default
-    end
-  end
+  defp resolve_source(input), do: MicrowavepropWeb.LocationResolver.resolve(input)
 
   # --- Render helpers -------------------------------------------------
   #
diff --git a/lib/microwaveprop_web/live/map_live.ex b/lib/microwaveprop_web/live/map_live.ex
index 579bbd49..da5704df 100644
--- a/lib/microwaveprop_web/live/map_live.ex
+++ b/lib/microwaveprop_web/live/map_live.ex
@@ -784,7 +784,7 @@ defmodule MicrowavepropWeb.MapLive do
       typical_range_km: config.typical_range_km,
       extended_range_km: config.extended_range_km,
       exceptional_range_km: config.exceptional_range_km,
-      humidity_effect: to_string(config.humidity_effect),
+      humidity_effect: BandConfig.humidity_effect_label(config),
       freq_mhz: config.freq_mhz
     }
   end
diff --git a/lib/microwaveprop_web/live/path_live.ex b/lib/microwaveprop_web/live/path_live.ex
index 30b52c46..f03ca3a5 100644
--- a/lib/microwaveprop_web/live/path_live.ex
+++ b/lib/microwaveprop_web/live/path_live.ex
@@ -3,6 +3,7 @@ defmodule MicrowavepropWeb.PathLive do
   use MicrowavepropWeb, :live_view
 
   import MicrowavepropWeb.Components.SkewTChart
+  import MicrowavepropWeb.LiveHelpers, only: [parse_float: 2]
 
   alias Microwaveprop.Buildings.Index, as: BuildingsIndex
   alias Microwaveprop.Buildings.Loader, as: BuildingsLoader
@@ -13,8 +14,6 @@ defmodule MicrowavepropWeb.PathLive do
   alias Microwaveprop.Propagation.ProfilesFile
   alias Microwaveprop.Propagation.Scorer
   alias Microwaveprop.Propagation.SporadicE
-  alias Microwaveprop.Radio.CallsignClient
-  alias Microwaveprop.Radio.Maidenhead
   alias Microwaveprop.Repo
   alias Microwaveprop.Terrain.ElevationClient
   alias Microwaveprop.Terrain.TerrainAnalysis
@@ -203,7 +202,7 @@ defmodule MicrowavepropWeb.PathLive do
               score: score,
               factors: factors,
               band_label: band_config.label,
-              humidity_effect: humidity_effect_string(band_config)
+              humidity_effect: BandConfig.humidity_effect_label(band_config)
             }
 
           _ ->
@@ -428,55 +427,12 @@ defmodule MicrowavepropWeb.PathLive do
   defp build_ionosphere_readout(_band_mhz, _lat, _lon, _dist), do: nil
 
   defp resolve_location(input) do
-    input = String.trim(input)
-
-    cond do
-      input == "" ->
-        {:error, "Location is required"}
-
-      coordinate_pair?(input) ->
-        [lat_s, lon_s] = String.split(input, ",", parts: 2)
-        {lat, _} = Float.parse(String.trim(lat_s))
-        {lon, _} = Float.parse(String.trim(lon_s))
-        {:ok, %{lat: lat, lon: lon, label: "#{Float.round(lat, 3)}, #{Float.round(lon, 3)}", type: :coordinates}}
-
-      maidenhead?(input) ->
-        case Maidenhead.to_latlon(input) do
-          {:ok, {lat, lon}} -> {:ok, %{lat: lat, lon: lon, label: String.upcase(input), type: :grid}}
-          :error -> {:error, "Invalid grid square: #{input}"}
-        end
-
-      true ->
-        case CallsignClient.locate(input) do
-          {:ok, info} ->
-            {:ok,
-             %{lat: info.lat, lon: info.lon, label: String.upcase(info.callsign), grid: info.gridsquare, type: :callsign}}
-
-          {:error, reason} ->
-            {:error, "Could not find #{input}: #{reason}"}
-        end
+    case MicrowavepropWeb.LocationResolver.resolve(input) do
+      :empty -> {:error, "Location is required"}
+      other -> other
     end
   end
 
-  defp coordinate_pair?(input) do
-    case String.split(input, ",", parts: 2) do
-      [a, b] ->
-        match?({_, _}, Float.parse(String.trim(a))) and match?({_, _}, Float.parse(String.trim(b)))
-
-      _ ->
-        false
-    end
-  end
-
-  defp maidenhead?(input) do
-    String.length(input) >= 4 and String.length(input) <= 10 and
-      Regex.match?(~r/^[A-Ra-r]{2}[0-9]{2}/i, input)
-  end
-
-  defp humidity_effect_string(%{humidity_effect: :beneficial}), do: "beneficial"
-  defp humidity_effect_string(%{humidity_effect: :harmful}), do: "harmful"
-  defp humidity_effect_string(_), do: "neutral"
-
   # The grid is the single decoded output of ProfilesFile.read/1 — keys are
   # `{snapped_lat, snapped_lon}` tuples produced by ProfilesFile.snap/2.
   # We mirror the same snapping locally instead of round-tripping through
@@ -719,16 +675,6 @@ defmodule MicrowavepropWeb.PathLive do
     }
   end
 
-  defp parse_float(nil, default), do: default
-  defp parse_float("", default), do: default
-
-  defp parse_float(str, default) do
-    case Float.parse(str) do
-      {val, _} -> val
-      :error -> default
-    end
-  end
-
   defdelegate haversine_km(lat1, lon1, lat2, lon2), to: Microwaveprop.Geo
   defdelegate bearing_deg(lat1, lon1, lat2, lon2), to: Microwaveprop.Geo
 
diff --git a/lib/microwaveprop_web/live/rover_live.ex b/lib/microwaveprop_web/live/rover_live.ex
index 01eb28dd..2a05a27e 100644
--- a/lib/microwaveprop_web/live/rover_live.ex
+++ b/lib/microwaveprop_web/live/rover_live.ex
@@ -8,6 +8,8 @@ defmodule MicrowavepropWeb.RoverLive do
 
   use MicrowavepropWeb, :live_view
 
+  import MicrowavepropWeb.LiveHelpers, only: [parse_int: 2]
+
   alias Microwaveprop.Accounts.User
   alias Microwaveprop.Buildings.Index, as: BuildingsIndex
   alias Microwaveprop.Geocoder
@@ -900,13 +902,6 @@ defmodule MicrowavepropWeb.RoverLive do
 
   # ── Helpers ─────────────────────────────────────────────────────────
 
-  defp parse_int(v, default) do
-    case Integer.parse("#{v}") do
-      {n, _} -> n
-      :error -> default
-    end
-  end
-
   defp clamp(v, lo, hi), do: v |> max(lo) |> min(hi)
 
   defp band_label(band) do
diff --git a/lib/microwaveprop_web/live_helpers.ex b/lib/microwaveprop_web/live_helpers.ex
new file mode 100644
index 00000000..72e00c8b
--- /dev/null
+++ b/lib/microwaveprop_web/live_helpers.ex
@@ -0,0 +1,37 @@
+defmodule MicrowavepropWeb.LiveHelpers do
+  @moduledoc """
+  Small helpers shared across LiveView modules. Use sparingly — most
+  view-specific logic belongs in its own LiveView.
+  """
+
+  @doc """
+  Parses a value into a float, returning `default` for nil, empty, or
+  unparseable input. Accepts strings, numbers, or any value with a
+  `String.Chars` impl.
+  """
+  @spec parse_float(term(), float()) :: float()
+  def parse_float(nil, default), do: default
+  def parse_float("", default), do: default
+
+  def parse_float(value, default) do
+    case value |> to_string() |> Float.parse() do
+      {n, _} -> n
+      :error -> default
+    end
+  end
+
+  @doc """
+  Parses a value into an integer, returning `default` for nil, empty,
+  or unparseable input.
+  """
+  @spec parse_int(term(), integer()) :: integer()
+  def parse_int(nil, default), do: default
+  def parse_int("", default), do: default
+
+  def parse_int(value, default) do
+    case value |> to_string() |> Integer.parse() do
+      {n, _} -> n
+      :error -> default
+    end
+  end
+end
diff --git a/lib/microwaveprop_web/location_resolver.ex b/lib/microwaveprop_web/location_resolver.ex
new file mode 100644
index 00000000..15e049e6
--- /dev/null
+++ b/lib/microwaveprop_web/location_resolver.ex
@@ -0,0 +1,103 @@
+defmodule MicrowavepropWeb.LocationResolver do
+  @moduledoc """
+  Parses user-supplied location input into a normalized lat/lon map.
+
+  Accepted formats:
+
+    * `"32.9, -96.8"` — decimal coordinates (lat, lon)
+    * `"EM12kx"` — Maidenhead grid square (4–10 chars)
+    * `"W5XYZ"` — amateur callsign (resolved via QRZ + cache)
+  """
+
+  alias Microwaveprop.Radio.CallsignClient
+  alias Microwaveprop.Radio.Maidenhead
+
+  @type kind :: :coordinates | :grid | :callsign
+  @type resolved :: %{
+          required(:lat) => float(),
+          required(:lon) => float(),
+          required(:label) => String.t(),
+          required(:kind) => kind(),
+          optional(:grid) => String.t() | nil
+        }
+
+  @doc """
+  Resolves an input string. Returns `{:ok, resolved}`, `{:error, msg}`,
+  or `:empty` for nil/blank input — callers decide whether `:empty`
+  is an error or a no-op.
+  """
+  @spec resolve(String.t() | nil) :: {:ok, resolved()} | {:error, String.t()} | :empty
+  def resolve(nil), do: :empty
+
+  def resolve(input) when is_binary(input) do
+    trimmed = String.trim(input)
+
+    cond do
+      trimmed == "" -> :empty
+      coordinate_pair?(trimmed) -> resolve_coordinates(trimmed)
+      maidenhead?(trimmed) -> resolve_grid(trimmed)
+      true -> resolve_callsign(trimmed)
+    end
+  end
+
+  @doc "True when `input` parses as a `lat, lon` decimal pair."
+  @spec coordinate_pair?(String.t()) :: boolean()
+  def coordinate_pair?(input) do
+    case String.split(input, ",", parts: 2) do
+      [a, b] ->
+        match?({_, _}, Float.parse(String.trim(a))) and
+          match?({_, _}, Float.parse(String.trim(b)))
+
+      _ ->
+        false
+    end
+  end
+
+  @doc "True when `input` looks like a Maidenhead grid square (4-10 chars, AA00 prefix)."
+  @spec maidenhead?(String.t()) :: boolean()
+  def maidenhead?(input) do
+    len = String.length(input)
+    len >= 4 and len <= 10 and Regex.match?(~r/^[A-Ra-r]{2}[0-9]{2}/i, input)
+  end
+
+  defp resolve_coordinates(input) do
+    [lat_s, lon_s] = String.split(input, ",", parts: 2)
+    {lat, _} = Float.parse(String.trim(lat_s))
+    {lon, _} = Float.parse(String.trim(lon_s))
+
+    {:ok,
+     %{
+       lat: lat,
+       lon: lon,
+       label: "#{Float.round(lat, 3)}, #{Float.round(lon, 3)}",
+       kind: :coordinates
+     }}
+  end
+
+  defp resolve_grid(input) do
+    case Maidenhead.to_latlon(input) do
+      {:ok, {lat, lon}} ->
+        {:ok, %{lat: lat, lon: lon, label: String.upcase(input), kind: :grid}}
+
+      :error ->
+        {:error, "Invalid grid square: #{input}"}
+    end
+  end
+
+  defp resolve_callsign(input) do
+    case CallsignClient.locate(input) do
+      {:ok, info} ->
+        {:ok,
+         %{
+           lat: info.lat,
+           lon: info.lon,
+           label: String.upcase(info.callsign),
+           grid: info.gridsquare,
+           kind: :callsign
+         }}
+
+      {:error, reason} ->
+        {:error, "Could not find #{input}: #{reason}"}
+    end
+  end
+end
diff --git a/test/microwaveprop_web/live/eme_live_test.exs b/test/microwaveprop_web/live/eme_live_test.exs
index d7eedaf0..5840eb63 100644
--- a/test/microwaveprop_web/live/eme_live_test.exs
+++ b/test/microwaveprop_web/live/eme_live_test.exs
@@ -75,7 +75,7 @@ defmodule MicrowavepropWeb.EmeLiveTest do
       # Maidenhead.to_latlon's strict validator (subsquare "ZZ" isn't A-X).
       {:ok, _view, html} = live(conn, ~p"/eme?source=EM12ZZ")
 
-      assert html =~ "Invalid Maidenhead grid"
+      assert html =~ "Invalid grid square"
       refute html =~ "Antenna aim"
     end
 
@@ -170,7 +170,7 @@ defmodule MicrowavepropWeb.EmeLiveTest do
 
         # Either the loose maidenhead regex catches it (invalid grid
         # error) or it falls through to callsign lookup (not found).
-        assert invalid_html =~ "Invalid Maidenhead grid" or
+        assert invalid_html =~ "Invalid grid square" or
                  invalid_html =~ "Could not find",
                """
                Expected an invalid input to produce a validation error.
diff --git a/test/microwaveprop_web/live_helpers_test.exs b/test/microwaveprop_web/live_helpers_test.exs
new file mode 100644
index 00000000..dc6447d7
--- /dev/null
+++ b/test/microwaveprop_web/live_helpers_test.exs
@@ -0,0 +1,49 @@
+defmodule MicrowavepropWeb.LiveHelpersTest do
+  use ExUnit.Case, async: true
+
+  alias MicrowavepropWeb.LiveHelpers
+
+  describe "parse_float/2" do
+    test "returns default for nil and empty string" do
+      assert LiveHelpers.parse_float(nil, 1.5) == 1.5
+      assert LiveHelpers.parse_float("", 1.5) == 1.5
+    end
+
+    test "parses well-formed float strings" do
+      assert LiveHelpers.parse_float("3.14", 0.0) == 3.14
+      assert LiveHelpers.parse_float("-2.5", 0.0) == -2.5
+    end
+
+    test "parses integer strings to a float" do
+      assert LiveHelpers.parse_float("42", 0.0) == 42.0
+    end
+
+    test "returns default on garbage input" do
+      assert LiveHelpers.parse_float("nope", 7.0) == 7.0
+    end
+
+    test "accepts numbers via to_string conversion" do
+      assert LiveHelpers.parse_float(2.5, 0.0) == 2.5
+    end
+  end
+
+  describe "parse_int/2" do
+    test "returns default for nil and empty string" do
+      assert LiveHelpers.parse_int(nil, 5) == 5
+      assert LiveHelpers.parse_int("", 5) == 5
+    end
+
+    test "parses integer strings" do
+      assert LiveHelpers.parse_int("42", 0) == 42
+      assert LiveHelpers.parse_int("-7", 0) == -7
+    end
+
+    test "returns default on garbage input" do
+      assert LiveHelpers.parse_int("nope", 9) == 9
+    end
+
+    test "accepts integers via to_string conversion" do
+      assert LiveHelpers.parse_int(42, 0) == 42
+    end
+  end
+end
diff --git a/test/microwaveprop_web/location_resolver_test.exs b/test/microwaveprop_web/location_resolver_test.exs
new file mode 100644
index 00000000..aa51087e
--- /dev/null
+++ b/test/microwaveprop_web/location_resolver_test.exs
@@ -0,0 +1,67 @@
+defmodule MicrowavepropWeb.LocationResolverTest do
+  use ExUnit.Case, async: true
+
+  alias MicrowavepropWeb.LocationResolver
+
+  describe "resolve/1" do
+    test "returns :empty for nil and blank input" do
+      assert LocationResolver.resolve(nil) == :empty
+      assert LocationResolver.resolve("") == :empty
+      assert LocationResolver.resolve("   ") == :empty
+    end
+
+    test "parses comma-separated decimal coordinates" do
+      assert {:ok, resolved} = LocationResolver.resolve("32.9, -96.8")
+      assert resolved.kind == :coordinates
+      assert resolved.lat == 32.9
+      assert resolved.lon == -96.8
+      assert resolved.label == "32.9, -96.8"
+    end
+
+    test "tolerates extra whitespace around coordinates" do
+      assert {:ok, %{lat: 32.9, lon: -96.8}} = LocationResolver.resolve("  32.9 , -96.8  ")
+    end
+
+    test "parses Maidenhead grid squares (uppercase)" do
+      assert {:ok, resolved} = LocationResolver.resolve("EM12kx")
+      assert resolved.kind == :grid
+      assert resolved.label == "EM12KX"
+      assert is_float(resolved.lat)
+      assert is_float(resolved.lon)
+    end
+
+    test "uppercases callsign-shaped grid squares for the label" do
+      assert {:ok, %{label: "FN42"}} = LocationResolver.resolve("fn42")
+    end
+  end
+
+  describe "coordinate_pair?/1" do
+    test "true for two comma-separated floats" do
+      assert LocationResolver.coordinate_pair?("32.9, -96.8")
+      assert LocationResolver.coordinate_pair?("0,0")
+      assert LocationResolver.coordinate_pair?("-89.9999, 179.9999")
+    end
+
+    test "false for malformed input" do
+      refute LocationResolver.coordinate_pair?("EM12kx")
+      refute LocationResolver.coordinate_pair?("32.9")
+      refute LocationResolver.coordinate_pair?("a, b")
+      refute LocationResolver.coordinate_pair?("")
+    end
+  end
+
+  describe "maidenhead?/1" do
+    test "true for valid grid squares" do
+      assert LocationResolver.maidenhead?("EM12")
+      assert LocationResolver.maidenhead?("EM12kx")
+      assert LocationResolver.maidenhead?("em12kx99")
+    end
+
+    test "false for non-grid input" do
+      refute LocationResolver.maidenhead?("32.9, -96.8")
+      refute LocationResolver.maidenhead?("W5XYZ")
+      refute LocationResolver.maidenhead?("EM")
+      refute LocationResolver.maidenhead?("")
+    end
+  end
+end