Fix position overwrite by lower-precision data

_onPositionReceive() now checks precisionBits before updating a
node's position. Previously, any POSITION_APP packet would blindly
overwrite the stored position, even if the incoming data had lower
precision (e.g., a relayed map report with 13 bits overwriting a
direct GPS fix with 32 bits).

This caused nodes to show incorrect positions on the map when other
mesh nodes relayed their position at reduced precision.

Fixes #910

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: syn-ack-ai

meshtastic/__init__.py

@@ -179,8 +179,21 @@ def _onPositionReceive(iface, asDict):
             logger.debug(f"p:{p}")
             p = iface._fixupPosition(p)
             logger.debug(f"after fixup p:{p}")
-            # update node DB as needed
-            iface._getOrCreateByNum(asDict["from"])["position"] = p
+            # update node DB as needed, but only if new position has
+            # equal or better precision than what we already have.
+            # This prevents low-precision map reports from overwriting
+            # high-precision GPS positions in the node database.
+            node = iface._getOrCreateByNum(asDict["from"])
+            existing = node.get("position", {})
+            existing_precision = existing.get("precisionBits", 0) or 0
+            new_precision = p.get("precisionBits", 0) or 0
+            if existing_precision == 0 or new_precision >= existing_precision:
+                node["position"] = p
+            else:
+                logger.debug(
+                    f"Ignoring position update with lower precision "
+                    f"({new_precision} < {existing_precision}) for node {asDict['from']}"
+                )
 
 
 def _onNodeInfoReceive(iface, asDict):