Project#

Use this skill for geographic coordinate system and projection questions.

Scope#

• Explain what a CRS/projection is and why it matters.
• Compare common systems such as EPSG:4326, EPSG:3857, UTM zones, CGCS2000, GCJ-02, and BD-09.
• Recommend a target CRS based on the task: storage, web map display, measurement, analysis, or exchange.
• Review conversion plans and call out likely mistakes such as swapped axis order, wrong units, or datum mismatch.

Workflow#

1. Identify the source coordinate system, target coordinate system, and the actual job to be done.
2. State whether the user needs a geographic CRS, projected CRS, or a provider-specific offset system.
3. Call out the important differences: datum, units, axis order, extent, and whether the transform is exact or approximate.
4. Give a concrete recommendation with an EPSG code or named system when possible.
5. If the request involves local files or batch conversion, hand off execution details to qgis.

Answer Checklist#

• Name the source and target CRS explicitly.
• State units clearly: degrees vs meters.
• Mention whether the CRS is suitable for measurement, display, storage, or exchange.
• Warn when web map tiles use EPSG:3857 but input data is EPSG:4326.
• Warn that GCJ-02 and BD-09 are offset systems, not drop-in replacements for standard global CRS definitions.
• If accuracy matters, state whether a datum shift or local transformation model is required.

Common Rules#

• Prefer EPSG:4326 for interoperable storage and API exchange unless another CRS is required.
• Prefer a projected CRS in meters for distance, area, and buffering.
• Prefer the correct local projected CRS over Web Mercator for engineering or survey-style measurement.
• Do not guess a UTM zone from country alone; derive it from longitude and hemisphere.
• Do not assume all software uses the same axis order for EPSG:4326; some APIs expect lon,lat, others advertise lat,lon.

When Not to Use#

• Reverse geocoding or coordinates-to-address lookup: use geocode.
• Deterministic GIS execution on files: use qgis.
• CesiumJS globe rendering or camera/data-layer code: use cesium.
• Navigation routing, turn-by-turn directions, or POI reviews.

OpenClaw + ClawHub Notes#

• Keep examples generic and portable. Do not hardcode private datasets, machine paths, or tokens.
• Prefer standards-based names and EPSG identifiers over vendor-specific jargon.
• For clawhub.ai publication, keep examples reproducible and changelog/version updates semver-driven.

Reference Docs In This Skill#

• Read {baseDir}/references/common-systems.md when you need quick guidance on common CRS and projection tradeoffs.