Ezigrade (version 2)

Center Pivot Design

Please note:- this is preliminary documentation - pivot design routines are still in beta mode.
Wikipedia defines Center-pivot irrigation as "(sometimes called central pivot irrigation), also called waterwheel and circle irrigation, is a method of crop irrigation in which equipment rotates around a pivot and crops are watered with sprinklers. A circular area centered on the pivot is irrigated, often creating a circular pattern in crops when viewed from above".
In this design furrows are created in concentric rings and we wish to avoid standing water in the furrows. If you don't have circular furrows then a traditional ezigrade design will suffice and there is no need to read this particular tutorial.
We have been supplied with a Trimble multiplane file. So the first steps are as follows:
  1. Open up Ezigrade
  2. We need to create a new job. From File menu - click New and browse to the folder you wish to use. We are going to call the job "pivot1"
  3. Click on the Import button.
  4. Select the Multiplane text file option.
The file is imported. Ezigrade automatically creates the triangles etc and we should have the following natural surface: You can find the file "pivot1.cdsdat" in the ezigrade data file.
We now need to specify a pivot point or specify a new one. Click on tools and then "add pivot point". In this job we have set point 1746 to be the pivot point.
To create a design around the pivot; we need to perform the following operations with Ezigrade. The first operation is to create a new copy of the job where we create a new set of points that are spaced around in a circular pattern. We need to do this; as towards the center we often need more points to fix up the grades. Normally there are not too many points here. From the tools menu click on the "Interpolate Pivot" option. You are asked for a new job name. The center pivot point, bench marks, boundary points (code of "B") are transferred to the new job as well as the new points that are calculated at increasing radii of 10m and every 32 degs around the job.At present in this beta implementation these values are hard coded. Internal attributes are set which are the polar coordinates of radii, and distance around the pivot. The new job looks like this:
As before I suggest you view the job with triangles colored by height. This gives you an idea of how to setup the relevant sections to achieve our grading outcome. The following shows the height distribution with some idea's on what we need to do. Normally for these designs we have a road which we can use as high point or low point as a table drain.
In this preliminary design we have a road entering at the top. We intend to grade from each side of the road. It is up to the designer how the sections are to be layed out. We have sectioned this job into 3 parts. It is equally correct to only have 2 sections or more. This procedure is the same as for a traditional ezigrade design. The procedure is done in a previous example.
A summary of the procedure is.
  • draw in the edges of where we wish to place the field edges: use the Fields - Insert Field Edge routine
  • For the first section, click on the edges so that the edges make a closed section.
  • From the Field menu - click on Fields - Add field
  • Repeat so that we have 3 sections.
We should have something similar to this: The Bearing axis for each section do not make a lot of sense so at present, please ignore them.
In this design we want to restrict the grades around the pivot to be between 0.05 and 2 %. We are not too concerned about cross grades that are radii but will set them to be between -3 and 3%. In the design above the distance is increasing clockwise around the pivot. So we set the following parameters:
Section1:  Xmin -3% Xmax 3% Ymin -2% Ymax -.05%
Section2:  Xmin -3% Xmax 3% Ymin .05% Ymax 2%
Section3:  Xmin -3% Xmax 3% Ymin .05% Ymax 2%
We also want the job to be smoothed as well as graded to the above limits. However we don't want the smoothing to carry across the section edges. To achieve this we first need to select the common links. Move the mouse and do a left click on each respective link. They will turn green. Now from the Field menu click on the "Toggle Fence Links for Smoothing". Hit the escape key to unselect the Field links. These links now turn orange and they work as a fence when smoothing.
After running the Grading - Grading (circular pivot) menu item we get the following design surface.
For the purists - the joins between sections are still a bit messy. To improve this you can add some extra points along the boundaries between sections.  Select the appropriate field links by left clicking on link and then use the "Add Points Along Selected Links".
Re-doing the grading(triangle - based) shows the following:

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