AccuGradeTM - Grade Control System (GPS/ATS/Sonic/Cross Slope) Caterpillar

GPS Accuracy Mode - Set

The AccuGrade - Grade Control System continually generates estimates of the GPS position error. You can set the maximum value of the GPS error estimate that is acceptable for your application. If the GPS error estimate exceeds the limits defined for the selected mode, a Low Accuracy GPS message is displayed.

There are three GPS accuracy levels, or modes:

• Fine

• Medium

• Coarse

Your site manager sets the limit for each mode, setting each mode to suit the type of work you are doing. (Your site manager can also deactivate the modes.) For example, the limits for Fine mode are set for finish trim work. If GPS accuracy is not within the tolerance set for Fine mode, do not change into Coarse mode to continue work on your final trim surface. Instead, do one of the following things:

• Wait for the GPS accuracy to improve and then continue in Fine mode.

• Change the GPS accuracy mode and then continue working on an area that does not require Fine mode GPS accuracy.

• Change the GPS accuracy mode and then raise the vertical offset to leave the constructed surface high. Return to the area when the GPS accuracy has improved and allows Fine mode operation. This lets you continue working on the same area of the design and not overcut the final design surface.

The GPS accuracy mode setting also determines what GPS accuracy is required before automatic controls can be activated. The GPS Accuracy Mode dialog displays a Yes in the Auto column if controls are available. Three text items that display the current GPS accuracy level can be displayed on the guidance views:

• H. GPS Err.

• V. GPS Err.

• GPS Acc. Mode

The color of the text item shows whether the current GPS error is within the selected GPS accuracy mode limits:

• The text item value remains black while the GPS error is less than 90 percent of the limit defined for the GPS accuracy mode.

• When the GPS error is approaching the defined limit, the text is blue.

• If the GPS error exceeds the limit of the GPS accuracy mode, the text is red.

Selecting The GPS Accuracy Mode

If you are using one or more GPS receivers as position sensors, make sure that the selected GPS accuracy mode is appropriate for the work you are about to do. To check and/or set the GPS accuracy mode, complete the following steps:

1. From any guidance screen, press the "GPS" soft key.

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2. Press Change Mode soft key to swap between fine, medium, and coarse accuracy modes.

3. Press "OK" to confirm the settings, or "ESC" to exit without saving.