CropObserver is to be positioned between 1 to 4 meters above the crop. A computer-controlled mirror system creates a rectangular measuring area containing more than 1.000 measuring points. At each measuring point a short pulse of laser light induces chlorophyll fluorescence emissions. A fluorescence sensor captures this signal in return. The first measurement covers all locations of the rectangular measuring area. Only locations with sufficient chlorophyll fluorescence signal are stored in the memory. In subsequent measuring cycles only these stored locations are measured. Since plants grow and move over time, at midnight (12 am) all locations of the rectangular measuring area are measured again and checked on fluorescence intensity. From the number of accepted measuring positions the projected plant area is calculated. At each laser spot the Fo and Fm is measured and from this data the efficiency of photosynthesis of Photosystem II is calculated. At the same time the light intensity from the PAR quantum sensor (Licor 400-700 nm), the global solar radiation from the pyranometer (Licor 400-1100 nm) and crop height is determined, using single-point optical laser triangulation. From PAR light and Fq’/Fm’, the relative ETR (Electron Transport Rate which correlates with CO2 uptake) is calculated. The CropObserver can be monitored remotely by a computer using the internet. It uploads its data to the letsgrow.com platform. On this platform all data from the CropObserver can be monitored and compared to other climate data.