qgis-agents-analysis-orchestrator

qgis-agents-analysis-orchestrator

Quick Reference

This skill is an orchestrator — it guides analysis method selection and workflow ordering. It does NOT contain implementation details. For implementation, refer to the specific skill indicated by the decision trees.

When to Use This Skill

Trigger	Action
"Analyze spatial data"	Start at Decision Tree 1: Analysis Type
"Which algorithm should I use?"	Go to Algorithm Selection Guide
"Chain multiple operations"	Go to Workflow Patterns
"What format should I use?"	Go to Format Selection
"Which CRS for my analysis?"	Go to CRS Selection
"Connect Claude to QGIS"	Go to MCP Integration

---

Critical Warnings

NEVER start coding before completing the workflow plan. ALWAYS determine: (1) analysis type, (2) CRS, (3) input format, (4) algorithm chain, (5) output format.

NEVER mix vector and raster operations without explicit conversion steps. ALWAYS include rasterize/vectorize as a named step.

NEVER chain algorithms with mismatched CRS. ALWAYS reproject to a common CRS as the FIRST step.

NEVER use geographic CRS (EPSG:4326) for distance or area calculations. ALWAYS reproject to a projected CRS first.

NEVER assume third-party provider algorithms (GRASS, SAGA) are available. ALWAYS check availability with QgsApplication.processingRegistry().algorithmById() and fall back to native: algorithms.

NEVER hardcode file paths. ALWAYS use QgsProcessing.TEMPORARY_OUTPUT or 'memory:' for intermediate results.

ALWAYS wrap processing.run() in try/except for QgsProcessingException.

ALWAYS check layer.isValid() after loading any layer.

ALWAYS create spatial indexes (native:createspatialindex) before spatial queries on large datasets.

---

Decision Tree 1: Analysis Type Selection

What is your primary question?
│
├─ "How are features distributed spatially?"
│  └─ VECTOR ANALYSIS → Decision Tree 2
│
├─ "What is the value at this location?" / "How does a surface vary?"
│  └─ RASTER ANALYSIS → Decision Tree 3
│
├─ "What is the shortest/fastest route?" / "What areas are reachable?"
│  └─ NETWORK ANALYSIS → Decision Tree 4
│
├─ "How do two datasets relate spatially?"
│  ├─ Both datasets are vector → VECTOR OVERLAY → Decision Tree 2
│  ├─ Both datasets are raster → RASTER CELL STATISTICS → Decision Tree 3
│  └─ One vector + one raster → HYBRID ANALYSIS:
│     ├─ Extract raster values at vector locations → `native:rastersampling`
│     ├─ Summarize raster within vector zones → `native:zonalstatisticsfb`
│     └─ Convert vector to raster first → `gdal:rasterize` then Decision Tree 3
│
├─ "Create a continuous surface from point samples?"
│  └─ INTERPOLATION:
│     ├─ Sparse, irregular points → `native:tininterpolation`
│     ├─ Dense, regular points → `native:idwinterpolation`
│     └─ Event density visualization → `native:heatmapkerneldensityestimation`
│
└─ "Classify or cluster features?"
   └─ CLUSTERING:
      ├─ Known number of groups → `native:kmeansclustering`
      ├─ Unknown groups, density-based → `native:dbscanclustering`
      └─ Spatiotemporal data → `native:stdbscanclustering`