Improve coordinate handling and add configurable position sensitivity

- Fix zero coordinate handling to distinguish between invalid coordinates and valid 0.0 (equator/prime meridian)
- Add to_float_safe() function that preserves nil for proper coordinate validation
- Add comprehensive coordinate validation with descriptive logging in JavaScript
- Make position change threshold configurable via application config (default: 0.001°)
- Add extensive test coverage for edge cases including nil coordinates and equator crossing
- Improve robustness for real-world APRS coordinate edge cases

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

assets/js/hooks/info_map.js

@@ -11,7 +11,9 @@ export const InfoMap = {
     const symbolHtml = this.el.dataset.symbolHtml;
 
     // Validate coordinates
+    const callsign = this.el.dataset.callsign;
     if (isNaN(lat) || isNaN(lon)) {
+      console.warn(`InfoMap: Invalid coordinates lat=${lat}, lon=${lon} for ${callsign} during update`);
       return;
     }
 
@@ -61,7 +63,7 @@ export const InfoMap = {
 
     // Validate coordinates
     if (isNaN(lat) || isNaN(lon)) {
-      console.error("Invalid coordinates for InfoMap");
+      console.warn(`InfoMap: Invalid coordinates lat=${lat}, lon=${lon} for ${callsign}`);
       return;
     }
 

config/config.exs

@@ -37,6 +37,11 @@ config :aprsme, :cleanup_scheduler,
   # 6 hours in milliseconds
   interval: 6 * 60 * 60 * 1000
 
+# Configure position tracking sensitivity
+config :aprsme, :position_tracking,
+  # Position change threshold in degrees (~100 meters at equator)
+  change_threshold: 0.001
+
 config :aprsme,
   ecto_repos: [Aprsme.Repo]
 

lib/aprsme_web/live/info_live/show.ex

@@ -101,16 +101,32 @@ defmodule AprsmeWeb.InfoLive.Show do
 
   defp position_changed?(current_packet, new_packet) do
     # Compare lat/lon to see if position actually changed
-    current_lat = to_float(current_packet.lat)
-    current_lon = to_float(current_packet.lon)
-    new_lat = to_float(new_packet.lat)
-    new_lon = to_float(new_packet.lon)
+    current_lat = to_float_safe(current_packet.lat)
+    current_lon = to_float_safe(current_packet.lon)
+    new_lat = to_float_safe(new_packet.lat)
+    new_lon = to_float_safe(new_packet.lon)
 
-    # Consider position changed if coordinates differ by more than ~100 meters (0.001 degrees)
-    lat_diff = abs(current_lat - new_lat)
-    lon_diff = abs(current_lon - new_lon)
+    # If any coordinate is invalid, consider it a change
+    case {current_lat, current_lon, new_lat, new_lon} do
+      {nil, _, _, _} ->
+        true
 
-    lat_diff > 0.001 or lon_diff > 0.001
+      {_, nil, _, _} ->
+        true
+
+      {_, _, nil, _} ->
+        true
+
+      {_, _, _, nil} ->
+        true
+
+      {curr_lat, curr_lon, new_lat, new_lon} ->
+        # Consider position changed if coordinates differ by more than the configured threshold
+        threshold = Application.get_env(:aprsme, :position_tracking, [])[:change_threshold] || 0.001
+        lat_diff = abs(curr_lat - new_lat)
+        lon_diff = abs(curr_lon - new_lon)
+        lat_diff > threshold or lon_diff > threshold
+    end
   end
 
   # Expose for testing
@@ -186,6 +202,10 @@ defmodule AprsmeWeb.InfoLive.Show do
     r * c
   end
 
+  # Safe float conversion that preserves nil for invalid coordinates
+  defp to_float_safe(value), do: EncodingUtils.to_float(value)
+
+  # Legacy float conversion that defaults to 0.0 for backward compatibility
   defp to_float(value), do: EncodingUtils.to_float(value) || 0.0
 
   defp format_timestamp_for_display(packet) do

test/aprsme_web/live/info_live/position_change_test.exs

@@ -43,5 +43,30 @@ defmodule AprsmeWeb.InfoLive.PositionChangeTest do
       new_packet = %{lat: Decimal.new("40.7200"), lon: Decimal.new("-74.0060")}
       assert Show.position_changed_for_test(current_packet, new_packet)
     end
+
+    test "handles coordinates at equator/prime meridian (0.0 is valid)" do
+      current_packet = %{lat: 0.0, lon: 0.0}
+      # Small change from valid 0.0
+      new_packet = %{lat: 0.0005, lon: 0.0}
+      refute Show.position_changed_for_test(current_packet, new_packet)
+    end
+
+    test "detects change when coordinates become invalid (nil)" do
+      current_packet = %{lat: 40.7128, lon: -74.0060}
+      new_packet = %{lat: nil, lon: -74.0060}
+      assert Show.position_changed_for_test(current_packet, new_packet)
+    end
+
+    test "detects change when coordinates become valid from invalid" do
+      current_packet = %{lat: nil, lon: -74.0060}
+      new_packet = %{lat: 40.7128, lon: -74.0060}
+      assert Show.position_changed_for_test(current_packet, new_packet)
+    end
+
+    test "handles both coordinates being invalid" do
+      current_packet = %{lat: nil, lon: nil}
+      new_packet = %{lat: nil, lon: nil}
+      assert Show.position_changed_for_test(current_packet, new_packet)
+    end
   end
 end