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| Everyone always says you need to be at the same speed when you exit the pass you are on and when you enter the next pass.
They are all wrong.
The display does not care about your speed when you exit a pass or are entering the next pass. It DOES however care whether you are accelerating or decelerating during a narrow period of time.
Let’s say your turn on time is 0.2 seconds. This means from the time the display send the command to turn the boom on to the time herbicide is hitting the ground is 0.2 seconds. Let’s further say that you spray at 16 mph. 0.2 seconds at 16 mph is 4.7 feet.
So if you’re traveling at 16 mph it is going to calculate that it needs to send the turn on signal 4.7 feet before arriving at the unsprayed area.
But what if you are accelerating hard during those 4.7 feet? Even worse, what if you were accelerating before and after those 4.7 feet?
The GPS speed readout has a lag but it is still used to calculate turn on and turn off times unless you have radar or wheel speed set as your primary.
So maybe you come out of your corner going 8 mph and you are accelerating to 16 mph.
During the critical phase where it calculates when to turn on. You are going 12 mph but it calculates 10 mph because of the lagging GPS speed.
So it says, “hey, 0.2 seconds at 10 mph is 2.9 feet”. So it turns on 2.9 feet before the unsprayed area. But you were actually going 12 mph when the calculation was made and you were accelerating to 16 mph so maybe in that 2.9 foot area you got up to 14 or 14 mph.
So you traveled a larger distance than the display thought you were going to travel for two reasons:
1. Due to lagging GPS speed, you were traveling faster than it thought you were when it made the calculation
2. Due to your acceleration, your speed (and therefore distance traveled) increased even more than the already incorrect calculation the display made
How do you avoid this? Make sure you are not accelerating not only at the point the display makes is decision on when to turn on, but also slightly before that point so that the lagging GPS speed has a chance to catch up and help the display make a good decision about when to turn on.
If you like to spray at a high speed and if you like to only make one headland pass, this might be impractical. You may need to make a second headland pass to make it easier to get this right. | |
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Ag Leader issue
