The Trimble FMX and TMX controllers use a fairly rudimentary file file format (.gps) to create files for grading. It contains the following elements

 

The original FMX controller only supports a fixed size file of about 1MB. So if you only have 5 points by 5 points, the file is the same size as a 300 by 300 point file. As a rough guide you can have roughly 500,000 points in the file if you only have a design. (ie about 700 by 700). If you also have a difference surface then your limit is about 250,000 points. (ie 500 by 500). However if you have a large number of strings then this reduces the size of the surfaces that will fit.

 

Also early FMX controllers were limited to a maximum of 1024 points in a row or column. No error as such, just rubbish on the screen.

 

The FMX/TMX controller displays the cut-fill surface as a colored surface. The design surface is not displayed. So if you only have a design surface then nothing is displayed. In this case it is rather useful to have some strings in the job so the operator knows where the surface is.

 

What to do if we only have a design surface and no strings

 

As mentioned the screen in the cab will only be showing the MB and any BM's. If we don't have any strings I normally would make some from contours. Assume we have the following job:

 

 

In this case the operator only needs the contours as a guide. He doesn't need this many. We need to recreate them further apart. So go to Contour ->  Surface Parameters. And change the major and Minor contour interval. In this case make it 10 and 2 instead of 1 and 0.5

 

 

We now have enough contours to show job outlines but not too much to overwhelm the FMX system.

 

 

At present the routines to create strings from contours are in the CDS program. So close the job in Ezigrade and open in CDS:

 

 

Now click on Contour -> Utilities -> Create Strings from Contours. A progress message is shown bottom left of the screen.

 

Turn off the contours and we have this:

 

 

Re-open the job in Ezigrade and Export -> Trimble Machine (.gps).

 

 

Make sure you have the "export visible strings" ticked and click Create. The file is created.

 

We have our own viewer. Go to www.foresoft.com and the link to the viewer is top left. We have a represenation as below:

 

 

You can see the string. In the cab you wont have the colored surface as FMX/TMX has no facility to display a design surface.

 

We want to grade the top right corner only

 

Assume we only want to grade the top right hand pad only and have a grid size of 1 foot. If we put in the numbers we can see that we end up with over a million points for the whole job and it wont fit.

 

When Ezigrade makes up the .gps export it uses the extents of the design surface. So an obvious solution is to restrict the size of the design surface. If you open the job in CDS under the Contour menu there is an option to set the extents of the triangulated surface. Set this and reform the contours. In this example you would also delete the strings copied from the contours and recreate them.

 

A second solution is to stay in Ezigrade and go to Contour -> Edit model -> Select Triangle by Polygon. Select all the triangles on the left and hit the delete key. Repeat for those triangles under the pad and again hit delete. Fix up the contour strings if necessary.

 

A third solution and the least effort is as follows.  Click in a new section around the pad. Click on Fields -> Field Edge and left click on the screen. Move the mouse and left click again. Go around the pad and left click on top of the start point. To finish the process hit the Enter key. If you mess up hit the escape key.

 

We have this and you can see Section1.

 

 

Now go to Export -> Trimble Machine and we have this: Take note of the Export 1 section only and filled in with "Section 1"

 

 

 

Our 1 foot grid now fits. Hit create. We only have the top right gridded. We do have some strings over the whole job. At present any string that goes through the section is drawn in full.

 

 

How to Rotate the Grid

 

If you are creating a road or drain or some other linear feature it is often handy to create a rotated grid. To do this use the Grid that is controlled from the left. If you cant see the grid select the Grid Pane on the left and hit reset. You can see the green cells. You can click on the grid and drag and rotate it. The cell size doesn't matter here. So we will square it up with the pad.

 

 

and we have.

 

 

Please note that you can type in the bearing of the grid in decimal degrees.

 

Now if you create the Trimble .gps file:

 

 

we have this:

 

 

One thing to look for with the rotation. The grid at present doesn't compenate for the distance between our grid north here and true north that the Trimble controller uses. Here we are using a State Plane coordinate system and there is no discernable difference. For WGS84 near the edge of the zone it is visible. So you may need to correct the grid roation depending on the grid convergence.