Sensor

Spectral bands

Different sensors capture different parts of the electromagnetic spectrum. More bands means more analytical options.

Each coloured bar marks one band's wavelength extent. Narrow bands are targeted at specific absorption features; broad bands gather more light but discriminate less.

Fig. 1 Spectral bands sample specific portions of the electromagnetic spectrum. Different sensors carry different band sets; the choice of bands determines which analytics are possible. Sentinel-2's red-edge bands enable NDRE for precision agriculture; WorldView-3's coastal blue supports bathymetry; both Landsat and Sentinel carry SWIR for mineral and water content.

Most commercial optical sensors are either 4-band (red, green, blue, near-infrared) or 8-band (adding red-edge, coastal blue, yellow, and another NIR). WorldView-3 adds 8 SWIR bands. Hyperspectral sensors like Wyvern's Dragonette have 24+ contiguous narrow bands. Each spectral band sees a specific wavelength range and reveals different surface properties.

Common band purposes

Blue and green pick up water and atmospheric scattering. Red is absorbed by chlorophyll. Near-infrared is reflected by healthy vegetation cell structure. Red-edge sits at the steep transition between red and NIR and is sensitive to chlorophyll concentration. SWIR penetrates atmospheric haze and reveals mineral and water content.

What to ask

If the work goes beyond producing a pretty picture, start from the indices or analytics you plan to run. That tells you which bands you actually need, and sometimes reveals a use case that wasn't fully thought through.