Random Point Grading

Please note: Both the documentation and the program for this section are under construction. The basics are here but the program is to be refined and made more user friendly over the next month.

See some of the earlier tutorials for traditional collection or importing from a dwg or dxf file. I will briefly comment on collecting using a hand held GPS and the MEI laser system.

To collect data in this fashion a notebook computer with two serial ports is needed. If there are not two ports available a USB adapter can be used which converts a single USB port into two serial ports. Start up the program and create a new blank job. Under the entry menu select GPS and then GPS options. This dialog controls some of the parameters of how data is entered into the system. The two major options are to collect data at a pre-defined interval or to collect data when we are a certain distance from the previous point. In this case we are collecting data every 5 seconds. You can also set whether you wish the program to automatically zoom or automatically pan if desired. At present the Autozoom is recommended. You should note that you are free to zoom and pan manually while data is being collected.

We are now in a position to start the data collection. Under the GPS menu select the pickup option. This runs a separate program which has a job of simply collecting the raw data from the GPS and the laser system and combining the two. The program GpsDeskTop pops up. The first job is to set the communication parameters for both the GPS and the MEI laser. Under the edit menu of GpsDeskTop you will find the comm's parameters for both main and secondary ports. Set the main to match the communications parameters of the GPS and set the auxiliary to match the parameters of the laser system.

Make sure they are both turned on; and we are ready to collect data. Under the run menu select the MEI laser option. A dialog will appear. Once a valid GPS position is optained a value for northing and easting is displayed in the appropriate sections of the dialog. Also a height is read in from the auxiliary port for the height from the laser equipment. Once you are happy that data is being collected you are free to minimize the GpsDesktop program; it will run happily in the background.

Now is a good time to describe what is actually happening here. The hand held GPS needs to be outputting a NMEA GGA string. This is a common format that most hand held GPS systems output automatically. The latitude and longitude obtained are converted internally into northings and eastings. These are done using a UTM conversion. This has the advantage of being valid for all area except near the north and south poles. The height is obtained from the ascii string that the MEI laser system outputs. Once these values are obtained a string is passed using a messaging system supported by windows programs to the main program.

Back in the main program you will see that a new icon bar has appeared once we ran the GPS pickup. Starting from the left there is a stop/go icon. This turns off any GPS input if need be; and once off will turn it back on. To the right of this is an icon which brings up the option dialog mentioned before. In this way you can change the time interval or distance interval of points that are picked up. You will notice the new icon bar in the screen below. There are also some fields which show any local GPS coordinates as well as height and an error indication in red, orange or green if available.

It is now time to start up the tractor. However before we start driving anywhere a quick note. When we start to process the data and calculate volumes; we are going to need to know the perimeter of the field. This can be done back in the office. However if you find it easier to drive a tractor rather than a mouse here is a hint. You can define the perimeter by simply driving around it picking up points. If you look at the screen above this is exactly what we have done. However we have coded the points as we picked them up with a code of edge. To do this click on the modes button ( to the left of the layers button) and select the modes input screen. Set the code to be constant and type in a value of edge. The screen is seen below.

It is now time to simply drive around the internal part of the paddock picking up data points as we go. As a rule of thumb the smoother the paddock the less data points that we need. Thus you need to pick up more points in the rougher sections of the paddock compared to the smoother sections. Once you have finished picking up the points you should obtain a screen such as seen at left.

It is now time to head back to the office and process the results. The first thing is to select the random land grading dialog. Under the grading menu select the random dialog. You will see the dialog below as well as an outline of the job. The first thing to do is to create the bounding string around the job. Fill in the edit box that say's Perimeter code with the code that we defined in the field. In this case fill it in with the edge string. Press the create perimeter string button. If you didn't pick up the boundary points separately in the field then you can create the string in the office as follows. Select the points that make up the edge by point selection. Then by point alter set the codes of the outer edge points to edge.Go back into the random grading dialog and fill in the appropriate code. Then run create perimeter string as before. In this case as the points are not in increasing order the string will need to be fixed in string utilities - restring.

Once you have created the triangulated surface it is recommended that you contour the surface as a check that what is picked up accurately reflects the surface as displayed by the program.

Going back to the program we can now calculate the grades of the field. Press the grade button and the program will report the respective grades of the field of -.9% at 90 degrees and 0.641% at 0 degrees. At present quadrant bearings are not implemented in this section of the program. We can now print out a random points report which tells is some volumes and the difference in height between the picked up points and there new graded values. The display printout is seen below

The program also has the facility to create reports in a gridded format if that is required. Leave the random dialog up and now press on the gridded grading option. Both dialogs will be visible which is OK. Eventually the random dialog will be made a subsection of the gridded grading. Fill in the setup stuff. You will need to supply an origin as well as a grid size and the size both length and cross ways. Once this has been done you should be able to display the job with the grid overlayed. ( At present program runs slow here - this is to be looked at). You are now able to create the gridded cut/fill and elevation reports. In this case the volumes reported in the cut/fill use each appropriate grid in turn and use the triangles or parts there of that the grid overlays.

It is probably a good time to check that the design surface produced is valid as can be seen in the picture at right. To do this under contouring menu create a new surface and call it a design surface. Under surface area make sure that you select the intri radio button to use the bounding string. You can now triangulate and contour to obtain the contour plan shown.

If you wish to obtain a picture showing the amount of cut and fill you need to create a further surface which is defined by a difference. Under contour menu add a surface and select by difference. Again select the intri optin in surface area and create the triangles. Again you can create the difference contours. Here we have decided to produce a colored diagram showing the cut and fills by colors. Under contour parameters select the color dialog and fill in the defaults. You can now obtain the following on screen display which you can easily print on your bubble jet printer.