Anomaly Detection Service

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To protect the Green Renaissance canopy, the Nexus must act as an early-warning system. We achieve this by deploying a Python-based Anomaly Detection Service. This service periodically queries the Sentinel Hub Statistical API, calculates the mean NDVI for a specific field, and triggers a localized alert if values dip below the critical 0.4 threshold.

The “Vitality Guard” Logic

The script follows a “Sensing-to-Signaling” flow. It is designed to run as a scheduled task (Cron job) within the TDCC infrastructure.

Python Script: `ghl_anomaly_alert.py`

Python

import requests
import json
from datetime import datetime, timedelta

# --- CONFIGURATION ---
SENTINEL_HUB_CLIENT_ID = "YOUR_CLIENT_ID"
SENTINEL_HUB_CLIENT_SECRET = "YOUR_CLIENT_SECRET"
NDVI_THRESHOLD = 0.4
CULTIVATOR_ALERT_WEBHOOK = "https://alerts.planethemp.one/webhook"

# Field Polygon (e.g., a specific farm in Antwerp)
FIELD_GEOMETRY = {
    "type": "Polygon",
    "coordinates": [[[4.42, 51.24], [4.43, 51.24], [4.43, 51.25], [4.42, 51.25], [4.42, 51.24]]]
}

def get_access_token():
    """Authenticates with Sentinel Hub OAuth2."""
    data = {
        "client_id": SENTINEL_HUB_CLIENT_ID,
        "client_secret": SENTINEL_HUB_CLIENT_SECRET,
        "grant_type": "client_credentials"
    }
    response = requests.post("https://services.sentinel-hub.com/oauth/token", data=data)
    return response.json()['access_token']

def check_ndvi_vitality():
    """Queries the Statistics API for the latest NDVI average."""
    token = get_access_token()
    headers = {"Authorization": f"Bearer {token}"}
    
    # Statistical API Request Payload
    payload = {
        "input": {
            "bounds": {"geometry": FIELD_GEOMETRY},
            "data": [{"type": "S2L2A"}]
        },
        "aggregation": {
            "timeRange": {
                "from": (datetime.now() - timedelta(days=5)).isoformat() + "Z",
                "to": datetime.now().isoformat() + "Z"
            },
            "aggregationInterval": {"of": "P1D"},
            "evalscript": """
                //VERSION=3
                function setup() {
                  return {
                    input: [{ bands: ["B04", "B08", "SCL"] }],
                    output: [{ id: "stats", bands: 1 }]
                  };
                }
                function evaluatePixel(samples) {
                  let ndvi = (samples.B08 - samples.B04) / (samples.B08 + samples.B04);
                  return [ndvi];
                }
            """
        }
    }

    response = requests.post("https://services.sentinel-hub.com/api/v1/statistics", json=payload, headers=headers)
    stats = response.json()['data']
    
    if stats:
        latest_avg = stats[-1]['outputs']['stats']['bands'][0]['stats']['mean']
        
        if latest_avg < NDVI_THRESHOLD:
            trigger_alert(latest_avg)
        else:
            print(f"✅ Vitality Check Passed: NDVI at {latest_avg:.2f}")

def trigger_alert(value):
    """Sends an automated emergency signal to the Cultivator."""
    alert_payload = {
        "level": "CRITICAL",
        "message": f"🚨 BIOMASS ANOMALY DETECTED. NDVI dropped to {value:.2f}.",
        "action_required": "Inspect field for irrigation failure or pest stress immediately.",
        "timestamp": datetime.now().isoformat()
    }
    requests.post(CULTIVATOR_ALERT_WEBHOOK, json=alert_payload)
    print(f"⚠️ Alert Dispatched! Current NDVI: {value:.2f}")

if __name__ == "__main__":
    check_ndvi_vitality()

3. Strategic Enhancements

Cloud Filtering: The evalscript above includes the Scene Classification Layer (SCL). In a production version, we filter out pixels marked as “Cloud” or “Cloud Shadow” to avoid false positives during heavy weather.
The “Critical Growth” Window: The Nexus can be configured to only run this script during the high-sequestration window (typically Days 30–90 of the hemp lifecycle), where an NDVI drop indicates a high risk to the Global Hemp Ledger’s collateral.
Smart Contract Integration: If an anomaly persists for more than 3 consecutive satellite passes, the Nexus can automatically adjust the “Risk Rating” of the associated $HEMP$ tokens on-chain.