Google Earth use satellite images but it is updated in a very low frequency (The image shown was captured in 2012), or in another word, it has a very low temporal resolution. Hence it is not a valid way of monitoring your crops using Google Earth
You decide to use aerial photos You contact a aerial photography company and get a very high-resolution image of your farm taken. You checked everything and they are all in perfect condition.
One week after… You received a bill from the aerial photography company
You decide to use satellite images You found out that when you displayed the satellite image, there are many “bands” available. You chose to display ATrue color image BFalse color image CSomething amazing
True color image True color image is displaying red stuff as red, green as green and blue as blue, i.e. the color in real world. You checked your crops in true color image, but you are not sure if they are all healthy or not, since they all appear to be green.
False color image False color image use blue to displayed green stuff, red to display blue, and red to display Near Infrared (NIR, an invisible type light but can be captured by sensors). Sounds confusing, but actually it would be very helpful to you.
In this case, your healthy crops would be appears to be bright red because it reflects lots of NIR back to the sensor. While the unhealthy crops will have a color
You can not only display bands in different combination, but also use it to produce more complicated image which would be able to describe the health condition of your crops more accurately.
NDVI is Normalized Difference Vegetation Index.. It is calculated by using Near Infrared and red light reflectance. It would be a better indicator of healthy crops.
Now you have learned how to monitor your farm properly