Suppress duplicate YOLO tile detections

backend/README.md

@@ -360,6 +360,7 @@ YOLO_DEVICE=cpu
 YOLO_IMAGE_SIZE=640
 YOLO_MAX_TILES=100
 YOLO_MAX_DETECTIONS=1000
+YOLO_DUPLICATE_IOU_THRESHOLD=0.5
 YOLO_BATCH_SIZE=1
 ```
 
@@ -389,6 +390,13 @@ The preflight checks configuration, dependency availability, local model file ex
 `1000` because dense building AOIs can exceed the upstream default cap of 300
 detections before QA/QC can measure recall honestly.
 
+`YOLO_DUPLICATE_IOU_THRESHOLD` controls GeoIntel-side cross-tile duplicate
+suppression after YOLO pixel boxes are converted to EPSG:4326 polygons and
+before `Detection` rows are persisted. Candidates are sorted by confidence per
+class; lower-confidence same-class candidates with geometry IoU greater than or
+equal to the threshold are suppressed. The default is `0.5`; set `0` to disable
+this post-processing for debugging.
+
 The same read-only status is available through the API and Detection Lab UI:
 
 ```bash
@@ -458,7 +466,8 @@ bash scripts/run_detection_calibration_sweep.sh http://192.168.10.150:1202
 
 The sweep creates one real persisted workflow run per threshold, fetches the
 persisted `QualityCheck`/`Metric` rows and writes a `calibration_summary.json`
-with detection count, score, precision, recall, F1, mean IoU and false
+with persisted detection count, raw candidate count, suppressed duplicate count,
+duplicate IoU threshold, score, precision, recall, F1, mean IoU and false
 positive/negative counts. It is intended to tune confidence/IoU/model choices,
 not to add new inference behavior.