Harmonic NDVI Phenology (Kansas Cropland, 2020-2023)

phenology intermediate MODIS MOD13A2 16-day NDVI

Ground Truth

270
day-of-year
10.0%
Tolerance
3
Runs
3
Passed

Calibrated from GEE execution on 2026-03-29 (actual: 270.1 DOY). Will be validated against QGIS and folia outputs. Peak NDVI day-of-year derived from first-order harmonic fit to MODIS 16-day NDVI composites over central Kansas cropland. Peak timing varies by crop type and harmonic phase extraction method.

Run Results

Workflow Model Backend Status Answer Error Cost Latency
exec gold gee PASS 270.0596389972697 0.0% $0.000037 666ms
exec gold folia-rust PASS 270.0484619140625 0.0% --- 1ms
exec gold qgis PASS 270.048 0.0% --- 100ms

Requirements

Data Sources
  • MODIS MOD13A2 16-day NDVI (Collection 6.1)
Operations
harmonic_fit temporal_reduce

LLM Prompt

The prompt given to LLMs in single-shot workflow benchmarks.

Problem: Fit harmonic curves to MODIS NDVI time series over central
Kansas cropland (2020-2023) to determine peak growing season timing.

Method:
- Load MODIS MOD13A2 16-day NDVI composites
- Fit first-order harmonic (1 cosine + 1 sine term)
- Extract phase angle and convert to day-of-year for peak NDVI
- Report mean peak DOY across the AOI

Study area: -98.5, 38.0, -98.0, 38.5 (central Kansas).
Expected answer: approximately DOY 270 (late September).