There is a lot that goes on between static data collection which certainly is good to evaluate raw data coming from the hardware which most likely is worked over with on board firmware to improve performance and applying it to the earth.

Then you have software that one uses to get work down on earth.  I have watched GPS hardware/software evolve to a point that really lasers are not needed.  Since you asked.........for vertical machine control I use two software products....Field Level II from Trimble and various products from AMW/AGPS for vertical control also.  FLII has taken what used to be "laser planeing" from the Spectra Precision company they bought and applied GPS to that process.  AMW/AGPS product lines have features that go beyond laser planes of light. Trimble software only works with Trimble hardware and AMW/AGPS works with many different hardware products.  I am sure after you read my experiences below there are other stories out there to be conveyed.

What you need to take away from this thread is that......aside from technical studies I personally have experienced scraper and dirt blower control with slopes of .02% and know others that have done so as well.  That is .02 feet of rise over a run of 100 feet.  That is 1/4 inch (.02*12 inchs) per 100 foot of linear travel!  Yes water will run with that kind of slope even though that seems "flat".  Speaking of flat did you know you can run water up hill if you pile it deep enough?  That is called ponding and it has shown up all over the corn belt in recent years even in more arid parts of the western corn belt.  GIS data work on yield and elevation data has shown that for years, even in dry years, but in my area it has not been given much consideration until ponding became more visual to producers.

The results are amazing with the right combinations of products.  I sell and use what I and my customers need and will leave you with this..............done correctly you can have very good vertical control just like you can have very good horizontal control for steering.  And the common denominator of both is you need to tie the hydraulics in for maximum performance.  Chasing the light does not cut it especially on really "flat" slopes.

Arnie