Well, no. Precision agriculture is an integration of many components of the farming operation, all of them very much data driven.
Lets just take the example of variable rate fertilization, because its the one I'm most familiar with. In the case of winter wheat (hard red and white), there are 3 primary components determining both yield (kg/m^2) and protein (g/kg). They are the available water, the available nitrogen and the 'site index' which is generally related to soil depth, but slope and aspect also play into this.
So, if what you want to do is land on a very specific amount of protein, say 7.5% across all of your fields in a dryland cropping situation. You need to know how much much water is available at all points in your field; how much nitrogen is available at all points in your field; and what scalar to carry around for a given XY position in your field. Maybe think of the scalar as an 'X-factor' to multiply the result of Water*Nitrogen by to adjust for local conditions.
Wheat, grown in high water low nitrogen gets very tall and has low protein and higher yield (to an extent). Wheat grown in high nitrogen stays short, but has higher protein and lower yield (to an extent). So it becomes a trade off between protein % and yield, and the theoretical maximum is described by the site index.
Wrapping it all together. First, find a cooperative old kook of a farmer. Second, convince him to let you drill a hole in his up auger to mount a hyper spectral sensor. Third, duct tape/ bungee mount a LiDAR puck to the front of the combine. 4th, solder some leads into the on harvest yield monitor. 5th, mount a high quality GPS unit to the top of the harvester if you don't have one already (or can't access the NMEA stream). Add car batteries, some old notebook computers to get the data, and a few days to harvest. Boom. Now your combine is a fully integrated data collection platform. You now have a measurement of grain height at all locations in your field. You also have a measurement of protein content at all locations in your field (with a little PCA wizardry and some protein sampling). Combine the two and you now have a 'site-index' that is nitrogen/ available water independent that you can use in your variable rate drill to adjust the fertilization rate to match the site index (since you can control the fertilization rate and not the available water). This will give you fairly precise control and allow you to more or less homogenize the overall protein content of the field. Alternatively, you could also optimize for yield (allowing protein to fluctuate).