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Plan 02: Dynamic Tiler Service (TiTiler)

Status: Pending Implementation
Date: 2026-02-27

Objective

Deploy a dynamic tiling service to serve Cloud Optimized GeoTIFFs (COGs) from MinIO as XYZ map tiles for the React frontend. This enables efficient map rendering without downloading entire raster files.

1. Architecture Overview

graph TD
    A[React Frontend] -->|Tile Request XYZ/zoom/x/y| B[Ingress]
    B --> C[TiTiler Service]
    C -->|Read COG tiles| D[MinIO]
    C -->|Return PNG/Tiles| A
    
    E[Worker] -->|Upload COG| D
    F[API] -->|Generate URLs| C

2. Technology Choice

2.1 TiTiler vs Rio-Tiler

Feature	TiTiler	Rio-Tiler
Deployment	Docker/Cloud Native	Python Library
API REST	✅ Built-in	❌ Manual
Cloud Optimized	✅ Native	✅ Native
Multi-source	✅ Yes	✅ Yes
Dynamic tiling	✅ Yes	✅ Yes
Recommendation	TiTiler	-

Chosen: TiTiler (modern, API-first, Kubernetes-ready)

2.2 Alternative: Custom Tiler with Rio-Tiler

If TiTiler has issues, implement custom FastAPI endpoint:

Use rio-tiler as library
Create /tiles/{job_id}/{z}/{x}/{y} endpoint
Read from MinIO on-demand

3. Deployment Strategy

3.1 Kubernetes Deployment

Create k8s/25-tiler.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: geocrop-tiler
  namespace: geocrop
  labels:
    app: geocrop-tiler
spec:
  replicas: 2
  selector:
    matchLabels:
      app: geocrop-tiler
  template:
    metadata:
      labels:
        app: geocrop-tiler
    spec:
      containers:
      - name: tiler
        image: ghcr.io/developmentseed/titiler:latest
        ports:
        - containerPort: 8000
        env:
        - name: MINIO_ENDPOINT
          value: "minio.geocrop.svc.cluster.local:9000"
        - name: AWS_ACCESS_KEY_ID
          valueFrom:
            secretKeyRef:
              name: geocrop-secrets
              key: minio-access-key
        - name: AWS_SECRET_ACCESS_KEY
          valueFrom:
            secretKeyRef:
              name: geocrop-secrets
              key: minio-secret-key
        - name: AWS_S3_ENDPOINT_URL
          value: "http://minio.geocrop.svc.cluster.local:9000"
        - name: TILED_READER
          value: "cog"
        resources:
          requests:
            memory: "512Mi"
            cpu: "250m"
          limits:
            memory: "2Gi"
            cpu: "1000m"
        livenessProbe:
          httpGet:
            path: /healthz
            port: 8000
          initialDelaySeconds: 10
          periodSeconds: 30
        readinessProbe:
          httpGet:
            path: /healthz
            port: 8000
          initialDelaySeconds: 5
          periodSeconds: 10
---
apiVersion: v1
kind: Service
metadata:
  name: geocrop-tiler
  namespace: geocrop
spec:
  selector:
    app: geocrop-tiler
  ports:
  - port: 8000
    targetPort: 8000
  type: ClusterIP

3.2 Ingress Configuration

Add to existing ingress or create new:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: geocrop-tiler
  namespace: geocrop
  annotations:
    nginx.ingress.kubernetes.io/proxy-body-size: "50m"
    cert-manager.io/cluster-issuer: letsencrypt-prod
spec:
  ingressClassName: nginx
  tls:
  - hosts:
    - tiles.portfolio.techarvest.co.zw
    secretName: geocrop-tiler-tls
  rules:
  - host: tiles.portfolio.techarvest.co.zw
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: geocrop-tiler
            port:
              number: 8000

3.3 DNS Configuration

Add A record:

tiles.portfolio.techarvest.co.zw → 167.86.68.48 (ingress IP)

4. TiTiler API Usage

4.1 Available Endpoints

Endpoint	Description
`GET /cog/tiles/{z}/{x}/{y}.png`	Get tile as PNG
`GET /cog/tiles/{z}/{x}/{y}.webp`	Get tile as WebP
`GET /cog/point/{lon},{lat}`	Get pixel value at point
`GET /cog/bounds`	Get raster bounds
`GET /cog/info`	Get raster metadata
`GET /cog/stats`	Get raster statistics

4.2 Tile URL Format

// For a COG in MinIO:
const tileUrl = `https://tiles.portfolio.techarvest.co.zw/cog/tiles/{z}/{x}/{y}.png?url=s3://geocrop-results/jobs/${jobId}/refined.tif`;

// Or with custom colormap:
const tileUrl = `https://tiles.portfolio.techarvest.co.zw/cog/tiles/{z}/{x}/{y}.png?url=s3://geocrop-results/jobs/${jobId}/refined.tif&colormap=${colormapId}`;

4.3 Multiple Layers

// True color (Sentinel-2)
const trueColorUrl = `https://tiles.portfolio.techarvest.co.zw/cog/tiles/{z}/{x}/{y}.png?url=s3://geocrop-results/jobs/${jobId}/truecolor.tif`;

// NDVI
const ndviUrl = `https://tiles.portfolio.techarvest.co.zw/cog/tiles/{z}/{x}/{y}.png?url=s3://geocrop-results/jobs/${jobId}/ndvi_peak.tif&colormap=ndvi`;

// DW Baseline
const dwUrl = `https://tiles.portfolio.techarvest.co.zw/cog/tiles/{z}/{x}/{y}.png?url=s3://geocrop-baselines/DW_Zim_HighestConf_${year}/${year+1}.tif`;

5. Color Mapping

5.1 Crop Classification Colors

Define colormap for LULC classes:

{
  "colormap": {
    "0": [27, 158, 119],    // cropland - green
    "1": [229, 245, 224],   // forest - dark green  
    "2": [247, 252, 245],   // grass - light green
    "3": [224, 236, 244],   // shrubland - teal
    "4": [158, 188, 218],   // water - blue
    "5": [240, 240, 240],   // builtup - gray
    "6": [150, 150, 150],   // bare - brown/gray
  }
}

5.2 NDVI Color Scale

Use built-in viridis or custom:

const ndviColormap = {
  0: [68, 1, 84],      // Low - purple
  100: [253, 231, 37], // High - yellow
};

6. Frontend Integration

6.1 React Leaflet Integration

// Using react-leaflet
import { TileLayer } from 'react-leaflet';

// Main result layer
<TileLayer
  url={`https://tiles.portfolio.techarvest.co.zw/cog/tiles/{z}/{x}/{y}.png?url=s3://geocrop-results/jobs/${jobId}/refined.tif`}
  attribution='&copy; GeoCrop'
/>

// DW baseline comparison
<TileLayer
  url={`https://tiles.portfolio.techarvest.co.zw/cog/tiles/{z}/{x}/{y}.png?url=s3://geocrop-baselines/DW_Zim_HighestConf_${year}/${year+1}.tif`}
  attribution='Dynamic World'
/>

6.2 Layer Switching

Implement layer switcher in React:

const layerOptions = [
  { id: 'refined', label: 'Refined Crop Map', urlTemplate: '...' },
  { id: 'dw', label: 'Dynamic World Baseline', urlTemplate: '...' },
  { id: 'truecolor', label: 'True Color', urlTemplate: '...' },
  { id: 'ndvi', label: 'Peak NDVI', urlTemplate: '...' },
];

7. Performance Optimization

7.1 Caching Strategy

TiTiler automatically handles tile caching, but add:

# Kubernetes annotations for caching
annotations:
  nginx.ingress.kubernetes.io/enable-access-log: "false"
  nginx.ingress.kubernetes.io/proxy-cache-valid: "200 1h"

7.2 MinIO Performance

Ensure COGs have internal tiling (256x256)
Use DEFLATE compression
Set appropriate overview levels

7.3 TiTiler Configuration

# titiler/settings.py
READER = "cog"
CACHE_CONTROL = "public, max-age=3600"
TILES_CACHE_MAX_AGE = 3600  # seconds

# Environment variables for S3/MinIO
AWS_ACCESS_KEY_ID=minioadmin
AWS_SECRET_ACCESS_KEY=minioadmin12
AWS_REGION=dummy
AWS_S3_ENDPOINT=http://minio.geocrop.svc.cluster.local:9000
AWS_HTTPS=NO

8. Security

8.1 MinIO Access

TiTiler needs read access to MinIO:

Use IAM-like policies via MinIO
Restrict to specific buckets

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {"AWS": ["arn:aws:iam::system:user/tiler"]},
      "Action": ["s3:GetObject"],
      "Resource": [
        "arn:aws:s3:::geocrop-results/*",
        "arn:aws:s3:::geocrop-baselines/*"
      ]
    }
  ]
}

8.2 Ingress Security

Keep TLS enabled
Consider rate limiting on tile endpoints

8.3 Security Model (Portfolio-Safe)

Two patterns:

Pattern A (Recommended): API Generates Signed Tile URLs

Frontend requests "tile access token" per job layer
API issues short-lived signed URL(s)
Frontend uses those URLs as tile template

Pattern B: Tiler Behind Auth Proxy

API acts as proxy adding Authorization header
More complex

Start with Pattern A if TiTiler can read signed URLs; otherwise Pattern B.

9. Implementation Checklist

Create Kubernetes deployment manifest for TiTiler
Create Service
Create Ingress with TLS
Add DNS A record for tiles subdomain
Configure MinIO bucket policies for TiTiler access
Deploy to cluster
Test tile endpoint with sample COG
Verify performance (< 1s per tile)
Integrate with frontend

10. Alternative: Custom Tiler Service

If TiTiler has compatibility issues, implement custom:

# apps/tiler/main.py
from fastapi import FastAPI, HTTPException
from rio_tiler.io import COGReader
import boto3

app = FastAPI()

s3 = boto3.client('s3',
    endpoint_url='http://minio.geocrop.svc.cluster.local:9000',
    aws_access_key_id=os.getenv('AWS_ACCESS_KEY_ID'),
    aws_secret_access_key=os.getenv('AWS_SECRET_ACCESS_KEY'),
)

@app.get("/tiles/{job_id}/{z}/{x}/{y}.png")
async def get_tile(job_id: str, z: int, x: int, y: int):
    s3_key = f"jobs/{job_id}/refined.tif"
    
    # Generate presigned URL (short expiry)
    presigned_url = s3.generate_presigned_url(
        'get_object',
        Params={'Bucket': 'geocrop-results', 'Key': s3_key},
        ExpiresIn=300
    )
    
    # Read tile with rio-tiler
    with COGReader(presigned_url) as cog:
        tile = cog.tile(x, y, z)
        
    return Response(tile, media_type="image/png")

11. Technical Notes

11.1 COG Requirements

For efficient tiling, COGs must have:

Internal tiling (256x256)
Overviews at multiple zoom levels
Appropriate compression

11.2 Coordinate Reference System

Zimbabwe uses:

EPSG:32736 (UTM Zone 36S) for local
EPSG:4326 (WGS84) for web tiles

TiTiler handles reprojection automatically.

11.3 Tile URL Expiry

For signed URLs:

Generate with long expiry (24h) for job results
Or use bucket policies for public read
Pass URL as query param to TiTiler

12. Next Steps

After implementation approval:

Create TiTiler Kubernetes manifests
Configure ingress and TLS
Set up DNS
Deploy and test
Integrate with frontend layer switcher

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