ECUTOFF

Sets satellite elevation cut-off for GPS satellites

Platform:

OEM719, OEM729, OEM7500, OEM7600, OEM7700, OEM7720, PwrPak7, CPT7, CPT7700, SMART7, SMART2

This command is used to set the elevation cut-off angle for tracked GPS satellites. The receiver does not start automatically searching for a GPS satellite until it rises above the cut-off angle (when satellite position is known). Tracked satellites that fall below the cut-off angle are no longer tracked unless they are manually assigned (see the ASSIGN command).

In either case, satellites below the ECUTOFF angle are eliminated from the internal position and clock offset solution computations.

This command permits a negative cut-off angle; it could be used in these situations:

• The antenna is at a high altitude, and thus can look below the local horizon

• Satellites are visible below the horizon due to atmospheric refraction

Care must be taken when using ECUTOFF command because the signals from lower elevation satellites are traveling through more atmosphere and are therefore degraded. Use of satellites below 5 degrees is not recommended.

Use the ELEVATIONCUTOFF command to set the cut-off angle for any system.

For dual antenna receivers, this command applies to both the primary and secondary antennas.

A low elevation satellite is a satellite the receiver tracks just above the horizon. Generally, a satellite is considered low elevation if it is between 0 and 15 degrees above the horizon.

There is no difference between the data transmitted from a low elevation satellite and that transmitted from a higher elevation satellite. However, differences in the signal path of a low elevation satellite make their use less desirable. Low elevation satellite signals have more error due to the increased amount of atmosphere they must travel through. In addition, signals from low elevation satellites don't fit the assumption that a signal travels in air nearly the same as in a vacuum. As such, using low elevation satellites in the solution results in greater position inaccuracies.

The elevation cut-off angle is specified with ECUTOFF to ensure that noisy, low elevation satellite data below the cut-off is not used in computing a position. If post-processing data, it is still best to collect all data (even that below the cut-off angle). Experimenting with different cut-off angles can then be done to provide the best results. In cases where there are not enough satellites visible, a low elevation satellite may actually help in providing a useful solution.

Message ID: 50

Abbreviated ASCII syntax:

ECUTOFF angle

Factory default:

ECUTOFF 5.0

ASCII example:

ECUTOFF 10.0

Field	Field type	ASCII value	Binary value	Description	Format	Binary bytes	Binary offset
1	Command header	-	-	ECUTOFF header This field contains the command name for abbreviated ASCII or the message header for ASCII or Binary.	-	H	0
2	angle	±90.0 degrees		Elevation cut-off angle relative to horizon	Float	4	H