NDVI (normalized difference vegetation index)

 

The objective of a vegetation index is to obtain a value that allows a quantitative evaluation of crop characteristics.

 With this index we can measure the interaction of the plant with solar radiation, this allows us to know the vigor of the crop and thus detect areas with weak development. 

 https://naxsolutions.com/diccionario-agricultura-de-precision/ndvi-beneficios-contras/

The NDVI is the most widely used index, it is easy to calculate and the information it provides is very useful. 

 It should be taken into account that this information is not concrete, but gives us an amalgam of biophysical factors such as: phenological state, physiological state, overture, phytosanitary, etc. 

 

We can calculate the NDVI index (ranging from -1 to 1) with the following expression:

NDVI = (NIR-Net) / (NIR + Net)

NIR = near infrared light

 Web= visible red light.

NDVI PROS

1. It helps us to detect abnormal changes in the growth process of the crop. 2.

2. Define vegetated areas

3. Distinguishes vegetation from soil 

4. Determine biophysical status (as mentioned above).  

 

NDVI LIMITATIONS

As we can see, the NDVI provides us with a lot of information, but it does not focus on a problem. This leads each technician, according to his experience in the field, to relate the types of NDVI values to the problems seen, the problem is not to generalize because it would surely be making a mistake.  

 

Cons of NDVI: 

1. Saturation, this index is very limited in certain phenological phases.

2. Soil effects.  

3. Atmospheric interference.

 

TIPS FOR NDVI INTERPRETATION

A plot as a whole will never be homogeneous because of the growing conditions in a living soil. Even so, what we must see physiologically is its behavior as homogeneous as possible. In situations where we have points of anomalous NDVI values is where we should go to study what is happening in the field.

 

The objective of NDVI alone is not to determine a type of problem, it is to determine an area where a problem potentially exists.

 

In NAX Solutions we have understood this, so we work not only not to give indexes but to give types of problems. Technology has limitations, but the goal is to know them in order to take them into account when establishing them.