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88 lines
1.9 KiB
Markdown
88 lines
1.9 KiB
Markdown
# Clip Worker
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Processes clip operations to extract features within a boundary.
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## Overview
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The clip worker extracts features from a dataset that intersect with a clipping boundary geometry.
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## Job Type
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`clip`
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## Input Parameters
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```json
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{
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"dataset_id": 123,
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"clip_geometry": {
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"type": "Polygon",
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"coordinates": [ ... ]
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},
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"output_dataset_id": 124
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}
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```
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### Parameters
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- `dataset_id` (required): Source dataset ID
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- `clip_geometry` (required): GeoJSON geometry for clipping boundary
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- `output_dataset_id` (required): Output dataset ID
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## Output
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Creates a new dataset with clipped features:
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- Features that intersect the clipping boundary
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- Geometry clipped to boundary
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- Original attributes preserved
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## Algorithm
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The worker uses PostGIS `ST_Intersection` to:
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1. Transform clipping geometry to dataset SRID
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2. Find features that intersect the boundary
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3. Clip geometries to boundary
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4. Store results in output table
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## Example
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```bash
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# Enqueue a clip job via API
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curl -X POST "https://example.com/api/datasets_clip_run.php" \
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-H "Content-Type: application/json" \
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-d '{
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"dataset_id": 123,
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"clip_geometry": {
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"type": "Polygon",
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"coordinates": [[[-180, -90], [180, -90], [180, 90], [-180, 90], [-180, -90]]]
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},
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"output_dataset_id": 124
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}'
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```
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## Background Jobs
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This analysis runs as a background job. The worker:
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1. Fetches queued `clip` jobs
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2. Validates input parameters
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3. Executes PostGIS clip queries
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4. Creates output dataset
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5. Marks job as completed
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## Performance Considerations
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- Processing time depends on dataset size and boundary complexity
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- Complex clipping boundaries may slow processing
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- Spatial indexes improve intersection performance
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- Consider simplifying geometries before clipping
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## Related Documentation
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- [Clip Analysis Tool](../analysis-tools/clip.md)
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- [Analysis API](../api/analysis.md)
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- [Workers Overview](index.md)
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