Hydrology Formulator vs SoilHue

HYDROLOGY FORMULATOR is the ultimate pocket reference for hydrologists, civil engineers, environmental scientists, and students. Packed with 1,000+ formulas, calculators, and conversions, it covers everything from groundwater analysis to stormwater design — all in one powerful app. HYDROLOGY CALCULATORS Infiltration & Recharge — 17 Calculators - Porosity, Green-Ampt Infiltration, Horton Infiltration, Philip Infiltration, Holtan's Model, Hydraulic Conductivity, Groundwater Recharge, Mean Pore Velocity, Specific Discharge, Volumetric Water Content, and more Evaporation & Transpiration — 8 Calculators - Penman-Monteith ET0, Blaney-Criddle ET, Thornthwaite PET, Crop Evapotranspiration, Saturation Vapor Pressure, Evaporation Rate of Lake, Relative Humidity, Potential Evapotranspiration Open Channel Flow — 12 Calculators - Manning's Equation (SI & US), Chezy Equation, Froude Number, Hydraulic Radius, Hydraulic Jump, Critical Depth, Specific Energy, Reynolds Number, and more Pipe Flow — 7 Calculators - Darcy-Weisbach Equation, Hazen-Williams Velocity (SI & US), Reynolds Number, Water Hammer Pressure, Continuity Equation, Minor Head Loss Stormwater & Watershed — 9 Calculators - SCS Curve Number Runoff, SCS Peak Discharge, IDF Rainfall Intensity, Kirpich Time of Concentration, Gumbel Extreme Value, Detention Storage Volume, Composite Curve Number, and more Pumps & Water Supply — 7 Calculators - Total Dynamic Head, Water Horsepower, Brake Horsepower, NPSHa, Affinity Laws for Flow, Head, and Power Weirs & Orifices — 6 Calculators - Rectangular Weir (SI & US), V-Notch Weir, Broad-Crested Weir, Orifice Flow, Spillway Discharge Water Flow — 10 Calculators - Water Flow Rate, Velocity of Water, Volume of Water Flow, 90° V-Notch calculations, Pipe Total Diameter, and more Surface Runoff — 6 Calculators - Average Velocity, Runoff, Travel Time, Hourly Rate of Rainfall Groundwater — 7 Calculators - Darcy's Law, Thiem Equation, Cooper-Jacob Drawdown, Dupuit Well Flow, Radius of Influence, Storage Properties Soil Pollution — 5 Calculators - Groundwater Pore Velocity, Effective Diffusion, Hydrodynamic Dispersion, Aquifer Parameter, Variance of Pore Velocity River Pollution — 7 Calculators - River Oxygen Deficit, Critical Time & Distance for Oxygen Deficit, Re-Aeration Constants, Dissolved Oxygen, River Flow, Water Temperature Lake Pollution — 4 Calculators - Waste Entering, Equilibrium Concentration, Settling Loss Rate, Particle Deposition Rate Sediment Transport — 4 Calculators - Shields Parameter, Bed Shear Stress, Stokes' Law Settling Velocity, Meyer-Peter Müller Bedload Snow Hydrology — 2 Calculators - Snow Water Equivalent, Degree-Day Snowmelt Culvert Hydraulics — 2 Calculators - Culvert Headwater (Outlet Control), Culvert Outlet Control Head Loss Flood Routing - Muskingum Routing Water Balance - Water Balance Equation, Storage Continuity Plus: Area Formulas, Pollution Cleanup, and more CONVERSIONS & REFERENCE Hundreds of built-in conversions across 16 categories including: - Liquid Measures, Cubic Measures, Linear Measures, Square Measures - Flow Rates, Pressures, Horsepower, BTU, Watts, Power - Hydraulic Conversions, Sand-to-Volume, Ft-Lbs - 8 Temperature Scales (Celsius, Fahrenheit, Kelvin, Rankine, Réaumur, Newton, Delisle, Rømer) - Metric Conversions and Fraction Conversions KEY FEATURES - Save and review past calculations - Switch between US (Imperial) and Metric units - Clean, intuitive interface designed for field and office use - Premium upgrade unlocks Groundwater, Pollution, Sediment Transport, Snow Hydrology, Culvert Hydraulics, and Flood Routing calculators

SoilHue identifies the Munsell color of a soil sample from a photograph taken with your device. It is built for pedologists, agronomists, geologists, archaeologists, conservators, soil-science students and anyone who works with soil color in the field. WHAT IT DOES • Calibrate the camera with an X-Rite ColorChecker Classic. SoilHue detects the card automatically inside your photo, rectifies its perspective, and computes a 3×3 correction matrix by least-squares fit over the 24 reference patches. • Take a photo of your soil sample (or pick one from your library) and select the area to analyze with a rectangle or a free-form polygon. • SoilHue averages the selected pixels in linear sRGB, applies your calibration matrix, and finds the closest match in CIE Lab among 293 chips derived from the official USDA Munsell renotation data. • Get the Munsell notation, an approximate USDA soil order (Histosol, Mollisol, Alfisol, Oxisol, Vertisol, Spodosol, Aridisol, Entisol, Inceptisol, Ultisol) and a short description. WHAT'S NEW IN 2.0 • 293 reference chips instead of 18. • ΔE94 in CIE Lab instead of Euclidean RGB. • Matrix 3×3 calibration replacing per-channel factors. • Automatic ColorChecker detection (Vision framework). • Printable calibration card (2-page A4 PDF, ICC sRGB). • Lighting check (warm/cool/atypical tint warning). • Real .xlsx export. • Accessibility, dark mode and stability improvements. DATA & PRIVACY • All analysis runs on-device. No image, sample or location ever leaves your phone. • Samples are stored locally in your app sandbox. iCloud sync is planned for a future release. • Location is captured only when you explicitly grant it. REQUIREMENTS • iPhone or iPad running iOS 17.6 or later. • A reasonably calibrated camera. Recommended: X-Rite ColorChecker Classic for best results. A basic calibration card is included for casual use. NOTES The USDA soil order classification is a heuristic orientation, not a definitive diagnosis — real classification depends on horizon, chemistry, texture and other field properties. Calibrations saved with versions before 2.0 are not compatible with the new color engine; the app will ask you to recalibrate. Contact: soilhue@ajgb.eu — Web: ajgb.eu/apps/soilhue