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Novella
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79 lines
1.7 KiB
Markdown
79 lines
1.7 KiB
Markdown
# Erase Analysis Worker
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Processes erase operations to remove features using another dataset.
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## Overview
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The erase analysis worker removes portions of features from an input dataset that overlap with features in an erase dataset.
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## Job Type
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`erase_analysis`
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## Input Parameters
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```json
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{
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"input_dataset_id": 123,
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"erase_dataset_id": 124
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}
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```
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### Parameters
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- `input_dataset_id` (required): Input dataset ID
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- `erase_dataset_id` (required): Erase dataset ID
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## Output
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Creates a new dataset with erased features:
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- Features with erased portions removed
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- Remaining geometry after erase operation
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- Original attributes preserved
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## Algorithm
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The worker uses PostGIS `ST_Difference` to:
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1. Find features that intersect the erase dataset
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2. Calculate difference (input - erase)
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3. Remove empty geometries
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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 an erase analysis job via API
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curl -X POST "https://example.com/api/analysis_erase_run.php" \
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-H "Content-Type: application/json" \
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-d '{
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"input_dataset_id": 123,
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"erase_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 `erase_analysis` jobs
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2. Validates input parameters
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3. Executes PostGIS erase operations
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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 sizes and overlap
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- Complex geometries may slow processing
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- Spatial indexes improve intersection performance
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- Consider simplifying geometries before erasing
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## Related Documentation
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- [Erase Analysis Tool](../analysis-tools/erase.md)
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- [Analysis API](../api/analysis.md)
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- [Workers Overview](index.md)
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