The contents of this page are no longer available.GPS Plot Layout Government of Alberta, Alberta Agriculture and Rural Development Government of Alberta, Alberta Agriculture and Rural Development, Policy and Environment, Agri-Environmental Integration and Engagement Government of Alberta, Alberta Agriculture and Rural Development 2002-11-25 2009-08-27 Soil/Water/Air`Integrated Cropping`Precision Farming Describes how a plot was laid out for tracking testing in the Lethbridge area using GPS eng news release 2001-10-16 Land Managers;Producers (Crops) www1 deptdocs sag 2004-09-23 , Government of Alberta, Alberta Agriculture and Rural Development Government of Alberta, Alberta Agriculture and Rural Development, Policy and Environment, Agri-Environmental Integration and Engagement Government of Alberta, Alberta Agriculture and Rural Development 2002-11-25 2009-08-27 Soil/Water/Air`Integrated Cropping`Precision Farming Describes how a plot was laid out for tracking testing in the Lethbridge area using GPS eng news release 2001-10-16 Land Managers;Producers (Crops) www1 deptdocs sag 2004-09-23

The Global Position System, or GPS, is a constellation of 24 satellites operated by the U.S. Department of Defense. With the proper receiver, radio signals transmitted from these satellites can enable the user to pinpoint their location to within 100 metres. The military introduces intentional errors into the signal to reduce the accuracy of civilian users, but using a second receiver over a known location can decrease the error to sub-metre level. A stationary receiver, called a base, is set up over a known location (such as a survey benchmark). The moving unit, or rover, is mounted on a truck, ATV, tractor, or even a backpack (as shown) to make it truly portable. A pair of FM radio modems is used as the real-time data link between the base and the rover. This is called differential GPS or DGPS since the base unit is correcting the position to the known location and applying the same difference to the rover unit. Engineering Services is currently using NovAtel AG-20 GPS receivers to achieve an accuracy of 20 cm or better.

Traditional methods for large plot layouts are now outdated thanks to GPS. In August, several 40-acre plots were laid out for tractor testing in the Lethbridge area. After choosing a starting point, a distance and bearing is used to calculate the next point in the plot. This location is entered into a handheld computer and can be navigated to. Stakes are placed along a line between the two points using the cross-track error to stay on course. Using this method, plots can be laid out by simply driving around the perimeter of the area one wants to mark. It can also be applied to grid soil sampling or to parallel track applications such as spraying or tillage to prevent costly misses and overlaps.

The Engineering in Agriculture Newsletter - Fall 1996
Doug Mackay, Project Engineer, Edmonton
 

GPS Plot Layout

 
 
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This information published to the web on October 16, 2001.