- Locking onto the row. OK so we have now seeded our crop in rows that are exactly one foot apart and in the rows the plants will be spaced evenly with 2 inch spacing. As soon as the seeds germinate and have small green shoots breaking through the surface of the soil, we can use these plants to locate and position vehicles and implements for subsequent operations such as weeding.
Using the analogy of a garden, with plants seeded in straight rows; as the plants germinate and surface, the row can be recognized. Anything that is green, and not in the row is, by default, a weed; it can and should be removed. The location of the rows also provides some guidance as where we can walk – we don’t want to stomp all over the good plants. Likewise, with the weeder; it is best to keep the wheels between the rows and off the good plants by locking onto the relative position of the rows to the wheels.
How is this locking process accomplished? With cameras. The implement will have a camera pointed straight down for where it would expect the row of crop to be. On the implement would be a red pointer or red thread, that indicates the implements, row center. When the camera has the red pointer in view, it indicates where in the camera’s field of view, the row should be: and therefore, the system can do a software calibration or row alignment without having to fine tune the camera’s mounting.
The frame of reference is our implement, and a red thread could be placed on our machine row center, and a blue thread could be the horizontal axis of our machine coordinate. The camera pointed straight down would see a red line, (vertical or y axis) and a blue line, (horizontal or x axis). This x,y coordinate system would have green pixels, and each glob of green pixels could be given a x,y coordinate. These coordinates could in turn be used to determine the row of good plants, and the offset of the machine-row to the actual row, and to position the weeds precisely relative to the implement. This would be necessary to remove individual weeds.
To detect the row of good plants, a histogram of all the green pixels in that vertical line of the cameras frame of view, would indicate where the dominant growth of plants would be – presumably the row of good plants. The horizontal histogram would have peaks (row) and a noisy floor (weeds in the midrow). The ratio of peak to floor values of the histogram would be a reliability factor in determining the confidence we have in acquiring the row. If we have a low reliability-factor we can use the seed spacing to further distinguish the position of the row, and to distinguish and precisely locate the good plants relative to our frame of reference. We also have six other rows that can help row discrimination. Since the rows are precisely one foot apart, we could average the row location of the seven rows on the machine to achieve an even more precise lateral position of the implement relative to the actual rows.
We also want a precise coordinate of all the bad plants, that are not in the grid row of good plants This can be done by using the implement as a frame of reference, and with each row camera providing a list of green blobs, each with an x,y coordinate. This weed and row location is useful information and has many uses:
- Used to steer and keep the wheels of the implement in between the rows.
- Placing the implement precisely over the rows for accurate activities such as:
- Weeding, water knife, or mechanical individual weed removal
- Working the soil, like roto-tilling or summer fallow between rows
- Chewing up trash between rows
- Watering, only the good plants
- Fertilizing, only where and when needed (shade of green of row)
- Sucking-up insects, and vacuuming the good plants
- Hilling the good plants
- Washing the good plants with a spray of water
- Applying fungicide accurately on only the good plants
These nursing and tending operations would start immediately after seeding. The weeding operation could be done with the seeding. When seeding, if there is a particular weedy patch; all the soil could be roto-tilled. How long would it take for an 8’ implement, traveling at 2 mph to work a quarter section? In one hour, it would cover a 32’ strip. Therefore, it would take 2640 / 32 = 82 hours or 3.43 days. Let’s say 4 or 5 days. Once finished it would turn around and start all over again, weeding and tending the crop. So maybe a dozen applications would be done for a single season in the first 60 days. The last 40 days, as the crop matures, may not need any applications.