How it works · for beginners
What the satellite sees, and what it can't
A short guide for anyone new to this. No background needed.
The short version
What the satellite sees
- A photo about every 5 days. Free European photo satellites pass over Nilabadi and take a photo of the area about every 5 days. FarmBot downloads these photos for free.
- Each photo is made of 10 m squares. One square is about the size of a small house plot. The satellite can't see single plants, only the average colour of each square.
- Greenness means a healthy, leafy crop. Healthy leaves reflect a lot of invisible light that cameras on the satellite can measure. From that, FarmBot works out a greenness score from 0 to 1. A bare field scores low. A thick green paddy crop scores high.
- Watching greenness week by week shows the crop's life. The score rises when the crop starts growing (green-up), is highest when it is fully grown (peak), and falls as it ripens and is harvested. These are the crop life stages.
- It also sees open water. A water score shows how much of the fishing pond has water on its surface.
Be careful
What it can't see
- Through clouds. In the monsoon the sky is often cloudy. Cloudy parts of a photo are thrown away (cloud removal). In July and August 2026 there were only one or two clear photos, so there are gaps just when the crop is planted. A radar satellite that sees through clouds may fill these gaps later.
- Pests and diseases, directly. Insects are far too small, and early disease doesn't change the colour of a 10 m square. Pest warnings will come from the weather (heat, rain and humidity that pests like). Later, sensors, insect traps and cameras on the fields will add ground checks. See Pest alerts.
- How much grain you'll get. Greenness only lets FarmBot compare this year with last year. It can't give a harvest weight in tonnes.
- Soil and rain on your own field. Soil and weather numbers on this site are computer estimates for a wider area. There is no rain gauge or soil test on the farm yet.
- Exact field edges. The outlines were traced by hand, not surveyed. Areas are approximate.
FarmBot is an experiment. It uses satellites only for now. Always trust what you see in the field first.
What the numbers mean
The numbers on this site, in plain words
| Number | What it means | Example from this site |
|---|---|---|
| Greenness score (0 to 1) | How green and leafy the crop looks. Under 0.4: dry or empty field. 0.4–0.65: young crop. 0.65 or more: fully green crop. | Temple plot on 23 Oct: 0.87, a fully green crop. |
| Water score | Whether a square is open water. Above 0 means water. | The fishing pond held 0.9–1.6 ha of open water all dry season. |
| Yield comparison score | This year's greenness against last year's, over the same dates. 1.00 = the same as last year. It is not tonnes of grain. | On 1–23 October the pond fields were less green than in 2025, and the temple plot greener. |
| Millimetres (mm) of rain | How deep the rain would stand on flat ground. | June–October 2026: about 1,402 mm. 6 months had under 25 mm. |
| Water pulled out by sun and wind | How much water heat and wind take out of wet ground, in mm. More than the rain means the field is drying out. | About 1,599 mm a year here. |
| Hectare (ha) | A unit of land, 100 m by 100 m. 1 ha is about 2.47 acres. | Temple plot: 7.47 ha (18.5 acres). Pond fields together: 1.51 ha (3.7 acres). |
| 10 m square | The smallest dot in a satellite photo. | Pond field A holds only about 100 of them, so detail inside a field is rough. |
The words Seen by satellite, Estimate and Experimental appear next to numbers across the site, so you know where each one comes from.
Word list
Every term on the site, explained
In alphabetical order. The technical name is shown small, in case you see it elsewhere.
- 10 m square
- The smallest square in a satellite photo, 10 m by 10 m (100 square metres). A field of 1 hectare holds about 100 of them. Squares on a field edge often mix in bunds or the next field.Technical name: Pixel
- Cloud removal
- Each photo comes with a map of which squares are cloud, cloud shadow or haze. Those squares are thrown away. A date counts only if most of the field is clear.Technical name: Cloud mask
- Crop life stages
- The crop's stages as seen from space: green-up (the crop starts growing and the field turns green), peak (the greenest point), and ripening (leaves turn yellow, so greenness falls before harvest).Technical name: Phenology
- Estimate
- Worked out by a computer weather or soil model for a big area, not measured on these fields. Good for trends, not for exact amounts.Technical name: Modelled
- Experimental
- A first try. It may change once ground checks or more seasons are available.Technical name: Experimental
- Greenness score
- How green and leafy the crop looks from space, on a scale from 0 to 1. Healthy, thick leaves reflect a lot of invisible near-infrared light, and the score uses that. On this site, under 0.4 means a dry or empty field, 0.4 to 0.65 a young crop, and 0.65 or more a fully green crop.Technical name: NDVI (Normalised Difference Vegetation Index)
- Half-way green date
- The rough date when the field got half-way from its dry-season low to its green peak.Technical name: Green-up (50% point)
- Haze-corrected photos
- The version of the photos that has been cleaned of haze in the air, so colours are closer to what the ground really looks like.Technical name: Level-2A (L2A)
- Hectare
- A unit of land area: 100 m by 100 m, or 10,000 square metres. 1 hectare is about 2.47 acres.Technical name: ha
- Humidity
- How much moisture is in the air, in per cent. 100% is fully saturated, like fog or dew.Technical name: RH (relative humidity)
- Land-use map
- A free 2021 map by the European Space Agency that labels every 10 m square as crop fields, trees, grass, buildings or water. FarmBot uses it to leave out trees, buildings and water near the plots.Technical name: ESA WorldCover 2021
- Lining up a screenshot
- Fitting a phone map screenshot onto real map positions by matching roads, ponds and tree clumps.Technical name: Georeferencing
- Metre map grid
- The map grid FarmBot's map files use. It measures position in metres, so areas and distances come out right. Readers of this site don't need it.Technical name: UTM zone 44N (EPSG:32644)
- Millimetres of rain
- How deep the water would be on flat ground if none soaked in or ran off. 25 mm in a month is very little. A heavy monsoon month here can bring several hundred.Technical name: mm
- Monsoon crop season
- The main rain-fed paddy season, roughly June to November.Technical name: Kharif
- NASA weather estimates
- Free daily weather estimates from NASA, the United States space agency, on a grid about 50 km wide.Technical name: NASA POWER
- Online photo catalogue
- The free online library from which FarmBot downloads the satellite photos. It lists every photo by date and place.Technical name: STAC catalogue, Microsoft Planetary Computer
- Open-Meteo
- A free weather service. FarmBot uses its rebuilt past weather for rain, soil wetness and water pulled out by sun and wind.Technical name: Open-Meteo historical weather
- Pheromone trap
- A small trap that uses a scent to attract the male moths of one pest. Counting the catch shows when that pest is active.Technical name: Pheromone trap
- Photo satellite
- A pair of free European satellites that photograph the area about every 5 days. They take photos in visible and invisible light. Each photo is made of 10 m by 10 m squares.Technical name: Sentinel-2
- Radar echo
- How much of the radar signal bounces back. Still water reflects it away, so a flooded field looks dark. It gets brighter as the crop grows.Technical name: Backscatter
- Radar satellite
- A free European radar satellite. Radar sends its own signal and sees through clouds, so it works in the monsoon. It shows standing water well. FarmBot has not used it yet.Technical name: Sentinel-1
- Ripening
- The stage when paddy leaves dry and turn yellow-brown as the grain fills. The greenness score falls steadily.Technical name: Senescence
- Seen by satellite
- Read directly from satellite photos of these fields.Technical name: Satellite-observed
- Smoothed line
- Single photos jump up and down because of haze and light. The smoothed line takes the middle value of all photos within 10 days either side of each date, so the trend is easier to see.Technical name: 20-day running median
- Soil wetness
- How much of the soil is water. It is shown for the top 7 cm and for 28 to 100 cm deep. These are computer estimates, not measured on the farm.Technical name: Soil moisture
- Spread band
- The shaded band around a line shows where the middle half of the field's squares fell on each date.Technical name: 25th to 75th percentile
- Water pulled out by sun and wind
- How much water the sun, heat and wind pull out of wet soil and plants each day, in millimetres. If this is more than the rain, the field is drying out.Technical name: ET0 (reference evapotranspiration)
- Water score
- How much open water or wetness shows in a spot. Above 0 means open water. There are two versions. They use slightly different colours of light and give slightly different pond sizes.Technical name: NDWI and MNDWI (water indexes)
- Weak patch
- A part of a field that stays less green than the rest, year after year. It could mean poor soil, waterlogging or pests, and is a place to go and look.Technical name: Weak zone
- Weather rebuilt by computer
- Past weather worked out by a computer from many weather stations and satellites, on a grid about 9 to 11 km wide.Technical name: Reanalysis
- Who's who in the sources
- ICAR is the Indian Council of Agricultural Research, the government's farm research body. NRRI is the National Rice Research Institute in Cuttack (its old name was CRRI). NCIPM is ICAR's National Centre for Integrated Pest Management. NICRA is ICAR's national project on climate-resilient farming. IIRR is the Indian Institute of Rice Research. IRRI is the International Rice Research Institute. IMD is the India Meteorological Department, the weather office. IPM means integrated pest management: scouting, traps, and spraying only when needed. LGD is the government's Local Government Directory of villages.Technical name: ICAR, NRRI (CRRI), NCIPM, NICRA, IIRR, IRRI, IMD, IPM, LGD
- Winter crop season
- The dry winter season after the paddy harvest. Crops such as green gram, black gram or mustard can be grown then if there is water.Technical name: Rabi
- World soil map
- A free world soil map from ISRIC (the International Soil Reference and Information Centre). It estimates soil type on a 250 m grid. It is a prediction, not a test of this soil.Technical name: ISRIC SoilGrids 2.0
- Year-to-year match score
- A number from -1 to 1 that says whether the same squares were low in both years. Near 1 means the same squares were low both times. Near 0, or below 0, means no pattern.Technical name: Spearman rank correlation
- Yield comparison score
- A score comparing how green this year's crop was against last year's, over the same dates. It is not a harvest weight in tonnes. 1.00 means the same as last year. Above 1 means greener. Below 1 means less green.Technical name: Relative yield index
Want the formulas? See Sources and method.