From: Development of an accurate low cost NDVI imaging system for assessing plant health
References | Approx. price (camera, filter and controllers) (GBP) | Pros | Cons | Advantage of NDVIpi |
---|---|---|---|---|
[59] | £360 | Two-camera seperation of Red/NIR; off-the-shelf consumer cameras; good quality optical filter | 2 or Less references | NDVIpi uses 6 references to account for non-linearity of consumer cameras; Lower-cost optical filter is used without detriment to accuracy |
[60] | £594 (excluding optical filters) | Two-camera seperation of Red/NIR; off-the-shelf consumer cameras; good quality optical filter; doesn't require calibration targets; vignetting correction | Requires on-site downwelling spectrometer | Programmable camera control; low-cost optical filter; can be customised and integrated with other systems; affordable reference targets |
[47] | £545 | Dual-band optical filter on a single camera; multiple references | No programmable control of camera, not easy to integrate with other systems | Programmable camera control; low-cost optical filter; can be customised and integrated with other systems |
[46] | £100 (excluding filters) | Two versions, one with a low-cost optical filter and one with a dual-pass optical filter; multiple references; single camera (no need for alignment) | No programmable control of camera. Leakage of NIR and Red (low-cost optical filter) due to single camera | Programmable camera control; low-cost optical filter; can be customised and integrated with other systems; low-cost filter; dual-camera to present NIR leakage |
[18] | £110 | Multiple References; Calibration to account for non-linearity; Two-camera seperation of Red/NIR | Requires camera modification | Programmable camera control; low-cost optical filter; can be customised and integrated with other systems; requires assembly |
[19] | – | Two-camera seperation of NIR and red; good quality optical filters | No calibration | Calibration methodology and multiple references; Lower-cost optical filter is used without detriment to accuracy |
[61] | £325 (£406 for reference targets) | Multiple References; Calibration to account for non-linearity; One camera with high quality optical filters |  | Programmable camera control; low-cost optical filter; low-cost reference targets; can be customised and integrated with other systems; calibration inherently accounts for gamma; correction (thus any camera can easily be used in the NDVIpi without requiring determination of the gamma correction) |
[62] | £200 (excl. filters) | Two-camera seperation of NIR and red; good quality optical filters | Requires on-site downwelling spectrometer | Calibration methodology and multiple references; Lower-cost optical filter is used without detriment to accuracy; an be customised and integrated with other systems |
[63] | £60 (excl. filters) | Raspberry Pi based; good quality optical filters; single camera system | 2 or Less references | NDVIpi uses 6 references to account for non-linearity of consumer cameras; Lower-cost optical filter is used without detriment to accuracy |
[48] | £785 | Good quality optical filters; single camera system | 2 or Less references | Low-cost reference targets; can be customised and integrated with other systems; calibration inherently accounts for gamma; correction (thus any camera can easily be used in the NDVIpi without requiring determination of the gamma correction) |
[12] | £968 | Narrowband filters over CCD camera; Good quality optics; Two camera seperation; Very similar to commercial cameras |  | Off-the-shelf components |
[64, 65] |  ~ £200 | Low-cost filters | Blue channel used for visible wavelengths; no hard seperation of VIS/NIR | Red wavelengths for NDVI calculation; two camera seperation; Programmable camera control; Six references |
[22] | £712 | Single Camera; No optical filters; algorithmically seperates NIR and visible images |  | Lower cost |