Every number we give you, every irrigation schedule, every pest alert, every fertigation recipe, is calculated from one of the equations below. We publish them here in full so your in-house agronomist or consulting engineer can audit our work at any time.
Satellite-derived indicators of crop health, biomass, chlorophyll, moisture, and stress. Computed from multispectral band ratios.
NDVI = (NIR − Red) / (NIR + Red)The most widely used measure of crop vigour. Output ranges from -1 to +1; healthy crops sit at 0.6 to 0.9. Used for overall canopy health, biomass estimation, and stress detection.
NDMI = (NIR − SWIR) / (NIR + SWIR)Measures canopy water content and detects early drought stress before visible wilting. Values below 0.2 signal water stress; above 0.4 indicates healthy moisture.
NDRE = (NIR − RedEdge) / (NIR + RedEdge)More sensitive than NDVI at high canopy densities. Saturates later, making it the go-to index for mid-to-late-season nitrogen and chlorophyll diagnosis on tree crops and dense canopies.
GNDVI = (NIR − Green) / (NIR + Green)More sensitive to chlorophyll concentration than NDVI. Particularly useful for nitrogen stress detection and for crops where NDVI saturates.
EVI = G × (NIR − Red) / (NIR + C1×Red − C2×Blue + L)Improves on NDVI by reducing atmospheric and soil-background noise. Better separation in dense canopies and more stable under variable aerosols.
SAVI = ((NIR − Red) / (NIR + Red + L)) × (1 + L)Corrects NDVI for soil brightness in sparse canopies. Critical in young plantations, after harvest, or in arid zones with bare-soil contribution.
LAI = −ln(1 − fPAR) / kTotal one-sided leaf area per unit ground. A key input for biomass and evapotranspiration modelling. Optimal values vary by crop (paddy 4-6, coconut 3-5, vegetables 2-4).
NDWI = (Green − NIR) / (Green + NIR)Detects open water, ponds, and waterlogged areas. Used to map farm ponds, monitor reservoir levels, and flag drainage issues after rainfall events.
Equations that drive irrigation scheduling, evapotranspiration modelling, and microclimate control.
ETc = Kc × ET₀ET₀ = f(Rn, G, T, u₂, es, ea, Δ, γ)Combines soil evaporation and plant transpiration to estimate daily crop water demand. The reference ET₀ is scaled by a crop coefficient Kc that changes with growth stage. Primary input for irrigation scheduling.
VPD = SVP(T) − AVPSVP(T) = 0.6108 × e(17.27T / (T + 237.3))Measures the drying power of the air. Optimal VPD for most crops is 0.8 to 1.2 kPa. Above this, stomata close and growth halts. Essential for polyhouse fogging and fan-pad control decisions.
Peff = P × (125 − 0.2×P) / 125Portion of gross rainfall that is actually usable by the crop after runoff, deep percolation, and canopy interception. Drives the irrigation offset: Deficit = ETc − Peff.
CWSI = (Tcanopy − Twet) / (Tdry − Twet)A 0 to 1 scale of crop water stress derived from canopy thermal imaging. 0 means fully watered, 1 means severe stress. Drone thermal or satellite LST pass feeds this calculation directly.
Thermal models and light equations that drive growth stage prediction, flowering timing, and harvest windows.
GDD = Σ [(Tmax + Tmin) / 2 − Tbase]Cumulative thermal units above a crop-specific base temperature. Used to predict germination, flowering, and maturity windows with precision. Essential for scheduling irrigation, fertiliser, and harvest labour.
PPFD = 0.45 × Rs × 4.57Amount of photosynthetically active light (400 to 700 nm) reaching the canopy, in μmol/m²/s. Derived from satellite solar radiation products using the 0.45 PAR fraction and the 4.57 μmol/J conversion factor.
Core equations used to design irrigation systems that deliver 95%+ distribution uniformity at minimum energy cost.
hf = 10.67 × L × (Q/C)1.852 / D4.87Head loss due to pipe friction, the dominant hydraulic loss in any farm irrigation network. Every pipe diameter in our designs is sized against this equation.
P1/γ + v1²/2g + z1 = P2/γ + v2²/2g + z2 + hLConservation of energy across any two points in a pipe system. Pressure head plus velocity head plus elevation head equals a constant, minus total losses hL.
DU = (Avg flow of lowest 25% / Overall average) × 100%Single most important quality metric for an irrigation system. Our designs target 95%+ for drip, 85%+ for sprinkler, and 75%+ for surface.
P (kW) = (Q × H × ρ × g) / (η × 1000)Electrical power the pump must deliver. Drives pump selection, electrical load calculation, and solar-plant sizing for off-grid farms.
ISO 9260 · BIS 15086 · FAO-56> 95% drip · > 85% sprinkler30 to 50%Up to 25%1 to 2 bar2.5 to 4 bar0.5 to 2.5 m/s< 5%The accuracy standards we commit to on every land survey, digital map, and topographic deliverable.
±1 to 5 cm±2 to 10 cm1 to 5 cm/pixel< 1:50002 to 5 cm/pixel±3 cm horizontal, ±5 cm verticalGeoTIFF · LAS · OBJWGS84 / UTM zone-specificShare your farm location and we'll return a baseline report with the exact values of these indices for your fields.
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