panel-map

name	panel-map
description	Deep Map panel knowledge: Leaflet lifecycle, NavSatFix/LocationFix/GeoJSON handling, tile layers, and the FilteredPointLayer pixel-deduplication grid that bounds rendering cost.

Panel Map Skill

A geographic visualization tool built on Leaflet for displaying GPS/NavSatFix data.

Structure

panels/Map/
├── MapPanel.tsx          # main panel, Leaflet lifecycle, PanelExtensionContext
├── FilteredPointLayer.ts # performance-critical point deduplication
├── support.ts            # message type detection (NavSatFix, GeoJSON, GPS)
└── config.ts             # settings tree, tile layer config

Leaflet Integration

• Map instance created on mount, destroyed on unmount
• Tile layers configurable (OpenStreetMap default, custom tile servers)
• Markers use FeatureGroup for efficient bulk operations
• View can follow the latest GPS point (auto-center)

FilteredPointLayer (Performance Critical)

Pixel-deduplication using a sparse 2D grid.

Problem

GPS at 10 Hz for 1 hour = 36,000 points. Rendering each as a Leaflet marker is prohibitively slow.

Solution

Screen space is divided into a sparse grid of pixel-sized cells.
Each cell holds at most ONE marker.
Points overlapping in screen space → only one is rendered.
On zoom change → the grid is recalculated.

Implementation

• Sparse 2D grid indexed by `${Math.floor(pixelX)},${Math.floor(pixelY)}`
• A new point mapping to an occupied cell is skipped (deduplicated)
• Result: O(visible pixels) markers instead of O(data points)
• Zoom in → more cells visible → more points; zoom out → heavy dedup → fast

Supported Message Types

Message Type	Fields Used
sensor_msgs/NavSatFix	latitude, longitude, altitude
sensor_msgs/msg/NavSatFix	(ROS 2 variant)
foxglove.LocationFix	latitude, longitude, altitude
GeoJSON	Feature / FeatureCollection geometry

Performance Notes

• FilteredPointLayer is the primary optimization — bounds rendering cost
• FeatureGroup enables bulk add/remove (single DOM update)
• Only the visible viewport bounds are processed
• Leaflet handles tile caching internally
• An upper bound on stored points prevents unbounded memory growth

Key Files

• packages/suite-base/src/panels/Map/MapPanel.tsx
• packages/suite-base/src/panels/Map/FilteredPointLayer.ts
• packages/suite-base/src/panels/Map/support.ts
• packages/suite-base/src/panels/Map/config.ts