SoilHue

Professional‑grade soil‑colour analysis, in your pocket

What is SoilHue?

SoilHue turns your iPhone or iPad into a field colourimeter: capture, analyse and classify soil samples using the Munsell colour system. Built for soil scientists, agronomists, environmental specialists, archaeologists, conservators — and anyone who works with the ground beneath our feet.

Key features

📷 Sample capture — take a photo (camera or library) and select the area to analyse with a rectangle or a free‑form polygon.
🎯 ColorChecker calibration — use an X‑Rite ColorChecker Classic; SoilHue detects the card inside your photo, rectifies its perspective, and computes a 3×3 correction matrix by least‑squares fit over the 24 reference patches.
🖨️ Printable calibration card — export a 2‑page A4 PDF with embedded ICC sRGB profile and corner fiducials. Print it at 100 % size and use it as a basic ColorChecker, no commercial card needed.
🌡️ Lighting check — after calibration, SoilHue analyses the gray patches and warns if the light is warm, cool or atypical, reminding you to take samples under the same light source.
🔬 Accurate Munsell classification — comparison in CIE Lab (ΔE94) against 293 reference chips derived from the official USDA Munsell renotation. Returns the Munsell notation (e.g. 10YR 4/3), an approximate USDA soil order and a short description.
📍 Local storage — samples stay on‑device, optionally tagged with GPS coordinates if you grant permission.
📤 Export — CSV (RFC 4180‑escaped), JSON or real Excel (.xlsx, not a renamed CSV) for spreadsheets or GIS workflows.
🌓 Full dark mode and VoiceOver accessibility throughout.
🔒 100 % private — all analysis runs on‑device. No photo, sample or location ever leaves your phone.

What's new in 2.0

Color engine fully rewritten: linear sRGB pipeline → ΔE94 in CIE Lab.
Munsell reference table grown from 18 to 293 chips.
Calibration via 3×3 matrix (replacing per‑channel diagonal factors).
Automatic ColorChecker detection (Vision + perspective correction).
Printable calibration card PDF with ICC sRGB OutputIntent.
Warm / cool / atypical lighting check.
Real Excel (.xlsx) export.
Full dark mode and accessibility improvements.

Heads‑up on upgrade: calibrations saved with versions before 2.0 are not compatible with the new color engine and are discarded automatically — the app will ask you to recalibrate on first launch. Your saved samples are preserved.

Docs & Privacy

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Contact

Questions, feedback or bug reports? Email us at soilhue@ajgb.eu.