Normalized Harvest Phenology Index (NHPI) is a remote sensing–based spectral index designed to estimate harvesting dates of corn and soybean using Google Earth Engine (GEE). This repository provides tools to apply NHPI for harvesting date detection based on user-defined analysis needs.

Try the NHPI demo here:
👉 https://ee-cuglyfrank.projects.earthengine.app/view/nhpi-demo

The interactive tool allows users to:

• Click on the map to sample a field
• Visualize the time series of NHPI, NDVI, and detected harvest date
• Adjust the NHPI threshold to examine its effect on harvesting date detection

Reminder: Each step may take time to process. Please wait for the result to appear before clicking again.

• 🟩 Interactive GEE Demo
  Hosted app for exploring NHPI-based harvesting date estimates (see link above).

• 🟨 Google Earth Engine JavaScript Code
  Full source code used in the analysis and visualization. 👉 NHPI-GEE

Yin Liu (yinl3@illinois.edu)

Chunyuan Diao (chunyuan@illinois.edu)

Remote Sensing Space-Time Innovation Lab

Department of Geography & GIScience, University of Illinois at Urbana-Champaign

This project is supported by the National Science Foundation’s Office of Advanced Cyberinfrastructure under grant 2048068 and 2518299.

If you use this work in any way, please mention this citation:

@article
{Title: A novel Normalized Harvest Phenology Index (NHPI) for corn and soybean harvesting date detection using Landsat and Sentinel-2 imagery on Google Earth Engine,
 Authors: Liu, Y., Diao, C., Yang, Z., Mei, W., Guo, T.,
 Publication: Remote Sensing of Environment,
 Year: 2025,
 Volume: 331,
 Page: 115016,
 DOI: 10.1016/j.rse.2025.115016 }