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import math
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from copy import deepcopy
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from django.conf import settings
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from django.db import transaction
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from .models import CropArea, CropZone
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EARTH_RADIUS_METERS = 6378137.0
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def get_chunk_area_sqm():
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raw_value = getattr(settings, "CROP_ZONE_CHUNK_AREA_SQM", 0)
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try:
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chunk_area = float(raw_value)
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except (TypeError, ValueError):
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chunk_area = 0
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if chunk_area <= 0:
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raise ValueError("CROP_ZONE_CHUNK_AREA_SQM must be a positive number.")
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return chunk_area
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def get_polygon_ring(area_feature):
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geometry = (area_feature or {}).get("geometry", {})
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coordinates = geometry.get("coordinates", [])
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if not coordinates or not coordinates[0]:
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raise ValueError("Area polygon coordinates are required.")
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return coordinates[0]
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def polygon_area_sqm(ring):
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if len(ring) < 4:
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return 0.0
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latitudes = [point[1] for point in ring]
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mean_latitude = math.radians(sum(latitudes) / len(latitudes))
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projected_points = []
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for longitude, latitude in ring:
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x = math.radians(longitude) * EARTH_RADIUS_METERS * math.cos(mean_latitude)
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y = math.radians(latitude) * EARTH_RADIUS_METERS
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projected_points.append((x, y))
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area = 0.0
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for index in range(len(projected_points) - 1):
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x1, y1 = projected_points[index]
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x2, y2 = projected_points[index + 1]
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area += (x1 * y2) - (x2 * y1)
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return abs(area) / 2.0
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def normalize_points(ring):
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if len(ring) > 1 and ring[0] == ring[-1]:
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ring = ring[:-1]
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return [[point[0], point[1]] for point in ring]
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def calculate_center(points):
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if not points:
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return {"longitude": 0.0, "latitude": 0.0}
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longitude = sum(point[0] for point in points) / len(points)
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latitude = sum(point[1] for point in points) / len(points)
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return {
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"longitude": round(longitude, 8),
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"latitude": round(latitude, 8),
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}
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def build_zone_square(area_points, center, zone_area_sqm):
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if len(area_points) < 4:
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return area_points
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width = math.sqrt(max(zone_area_sqm, 1))
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half_width = width / 2.0
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latitude_factor = 111320.0
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longitude_factor = 111320.0 * math.cos(math.radians(center["latitude"]))
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if longitude_factor == 0:
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longitude_factor = 1.0
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delta_lat = half_width / latitude_factor
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delta_lng = half_width / longitude_factor
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return [
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[round(center["longitude"] - delta_lng, 8), round(center["latitude"] - delta_lat, 8)],
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[round(center["longitude"] + delta_lng, 8), round(center["latitude"] - delta_lat, 8)],
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[round(center["longitude"] + delta_lng, 8), round(center["latitude"] + delta_lat, 8)],
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[round(center["longitude"] - delta_lng, 8), round(center["latitude"] + delta_lat, 8)],
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]
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def split_area_into_zones(area_feature):
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area_ring = get_polygon_ring(area_feature)
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area_points = normalize_points(area_ring)
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area_center = calculate_center(area_points)
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total_area_sqm = polygon_area_sqm(area_ring)
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chunk_area_sqm = get_chunk_area_sqm()
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zone_count = max(1, math.ceil(total_area_sqm / chunk_area_sqm))
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zones = []
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remaining_area = total_area_sqm
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base_longitude = area_center["longitude"]
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base_latitude = area_center["latitude"]
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for sequence in range(zone_count):
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zone_area_sqm = min(chunk_area_sqm, remaining_area) if sequence < zone_count - 1 else remaining_area
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if zone_area_sqm <= 0:
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zone_area_sqm = min(chunk_area_sqm, total_area_sqm)
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shift = (sequence - ((zone_count - 1) / 2)) * 0.0003
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zone_center = {
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"longitude": round(base_longitude + shift, 8),
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"latitude": round(base_latitude, 8),
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}
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zone_points = build_zone_square(area_points, zone_center, zone_area_sqm)
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zone_geometry = {
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"type": "Feature",
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"properties": {
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"zone_id": f"zone-{sequence}",
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"sequence": sequence,
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"area_sqm": round(zone_area_sqm, 2),
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"area_hectares": round(zone_area_sqm / 10000, 4),
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"center": zone_center,
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},
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"geometry": {
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"type": "Polygon",
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"coordinates": [[*zone_points, zone_points[0]]],
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},
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}
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zones.append(
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{
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"zone_id": f"zone-{sequence}",
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"geometry": zone_geometry,
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"points": zone_points,
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"center": zone_center,
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"area_sqm": zone_area_sqm,
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"area_hectares": zone_area_sqm / 10000,
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"sequence": sequence,
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}
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)
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remaining_area = max(0.0, remaining_area - zone_area_sqm)
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area_geometry = deepcopy(area_feature)
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area_geometry.setdefault("properties", {})
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area_geometry["properties"].update(
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{
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"center": area_center,
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"area_sqm": round(total_area_sqm, 2),
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"area_hectares": round(total_area_sqm / 10000, 4),
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}
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)
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return {
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"area": {
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"geometry": area_geometry,
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"points": area_points,
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"center": area_center,
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"area_sqm": total_area_sqm,
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"area_hectares": total_area_sqm / 10000,
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"chunk_area_sqm": chunk_area_sqm,
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"zone_count": zone_count,
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},
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"zones": zones,
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}
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def persist_zones(area_feature):
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zoning_result = split_area_into_zones(area_feature)
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area_data = zoning_result["area"]
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with transaction.atomic():
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crop_area = CropArea.objects.create(
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geometry=area_data["geometry"],
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points=area_data["points"],
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center=area_data["center"],
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area_sqm=round(area_data["area_sqm"], 2),
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area_hectares=round(area_data["area_hectares"], 4),
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chunk_area_sqm=round(area_data["chunk_area_sqm"], 2),
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zone_count=area_data["zone_count"],
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)
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CropZone.objects.bulk_create(
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[
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CropZone(
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crop_area=crop_area,
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zone_id=zone["zone_id"],
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geometry=zone["geometry"],
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points=zone["points"],
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center=zone["center"],
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area_sqm=round(zone["area_sqm"], 2),
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area_hectares=round(zone["area_hectares"], 4),
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sequence=zone["sequence"],
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)
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for zone in zoning_result["zones"]
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]
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)
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zoning_result["area"]["id"] = crop_area.id
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zoning_result["area"]["uuid"] = str(crop_area.uuid)
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return zoning_result
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