WGS84

WGS84

Use this skill for practical work with WGS 84 longitude/latitude coordinates.

WGS 84 usually refers to the global geographic reference system commonly exposed as EPSG:4326 in GIS software. It is the right default for GPS-style coordinate exchange, but it is not the right answer for every display or measurement workflow.

What This Skill Does

• Explain what WGS 84 is and when to use it.
• Validate longitude/latitude numeric ranges.
• Check whether a coordinate pair is likely lon,lat or lat,lon.
• Recommend a UTM zone and EPSG code for projected analysis.
• Flag when a coordinate falls inside mainland-China extents where GCJ-02 / BD-09 confusion is common.
• Recommend whether to keep WGS84, use Web Mercator for display, or switch to a projected CRS for analysis.
• Explain when to keep data in EPSG:4326 and when to reproject.
• Hand off file-based reprojection steps to qgis when execution is required.

Standard Workflow

1. Confirm whether the input is WGS 84 already, or just "GPS coordinates" by assumption.
2. State the expected tuple order explicitly: lon,lat or lat,lon.
3. Validate numeric ranges before discussing conversion.
4. Decide the task type:
   • storage or API exchange
   • web map display
   • distance/area/buffer analysis
   • regional engineering or survey workflow
5. Keep EPSG:4326 for exchange/storage unless the task needs projected units.
6. If analysis needs meters, recommend a suitable projected CRS such as a local CRS or UTM zone.

Practical Commands

Validate a WGS84 coordinate pair

python3 {baseDir}/scripts/wgs84_tool.py validate --lon 116.4074 --lat 39.9042

Check whether a pair is probably lon,lat or lat,lon

python3 {baseDir}/scripts/wgs84_tool.py guess-order --a 116.4074 --b 39.9042
python3 {baseDir}/scripts/wgs84_tool.py guess-order --a 39.9042 --b 116.4074

Recommend a UTM zone and EPSG code from WGS84 coordinates

python3 {baseDir}/scripts/wgs84_tool.py utm --lon 116.4074 --lat 39.9042
python3 {baseDir}/scripts/wgs84_tool.py utm --lon -122.478255 --lat 37.819929

Flag China mapping offset risk

python3 {baseDir}/scripts/wgs84_tool.py china-check --lon 116.4074 --lat 39.9042

Recommend the right CRS for a concrete task

python3 {baseDir}/scripts/wgs84_tool.py recommend --lon 116.4074 --lat 39.9042 --task exchange
python3 {baseDir}/scripts/wgs84_tool.py recommend --lon 116.4074 --lat 39.9042 --task analysis
python3 {baseDir}/scripts/wgs84_tool.py recommend --lon 116.4074 --lat 39.9042 --task web-map

Decision Rules

• Prefer EPSG:4326 for interoperable storage, APIs, logs, and exchange.
• Prefer a projected CRS in meters for buffering, area, distance, and nearest-neighbor analysis.
• Prefer EPSG:3857 only for web-map display compatibility, not for accurate measurement.
• Do not assume a pair is WGS 84 just because it contains two decimals; confirm source system when accuracy matters.
• Do not assume all systems interpret EPSG:4326 axis order the same way; many practical APIs use lon,lat even when standards prose differs.
• In mainland China workflows, explicitly check whether the source is raw WGS84 or app-level GCJ-02 / BD-09.
• Treat GCJ-02 and BD-09 as mapping offset systems, not simple aliases for EPSG:4326.

What To Return

• The interpreted coordinate order.
• Whether the values are valid WGS84 longitude/latitude ranges.
• Whether keeping EPSG:4326 is appropriate for the task.
• If not, recommend the target CRS and explain why.
• If using UTM, provide zone number, hemisphere, and EPSG code.
• If the point is in mainland China, include a short warning about GCJ-02 / BD-09 ambiguity when relevant.

When Not To Use

• Reverse geocoding or coordinates to address lookup: use geocode.
• File-based GIS conversion or batch reprojection: use qgis.
• General CRS comparison beyond WGS84-centered guidance: use project.
• Navigation routing, POI search, or map reviews.

OpenClaw + ClawHub Notes

• Keep examples generic and reproducible.
• Do not hardcode private paths, real device traces, or private datasets.
• For clawhub.ai publication, keep versioning/changelog semver-driven and examples standards-based.

Reference Docs In This Skill

• Read {baseDir}/references/wgs84-reference.md for concise CRS comparison and common failure cases.