GPS Sensor

Introduction

The V5 GPS (Game Positioning System™) Sensor provides accurate position and orientation tracking for a robot on the VEX Field. It uses the GPS Field Code around the Field’s perimeter to calculate the robot’s X and Y coordinates and heading in real time.

The GPS Sensor returns the robot’s position using a reference point automatically calculated from the offsets entered when configuring the GPS Sensor in the Devices window.

For more information about the GPS Sensor, read Using the GPS Sensor with VEX V5 in the VEX Library.

The reference point acts as the GPS Sensor’s own (0, 0) position where all coordinates, headings, and movements returned by GPS methods are relative to this configured point.

This page uses gps_sensor as the example GPS Sensor name. Replace it with your own configured name as needed.

Below is a list of available methods:

• calibrate – Calibrates the GPS Sensor to set its heading as the current drivetrain heading.

• set_origin – Sets the position of the reference point on the robot.

• set_location – Sets both the reference point’s position and heading on the Field.

• x_position – Returns the reference point’s x coordinate on the Field.

• y_position – Returns the reference point’s y coordinate on the Field.

• heading – Returns the reference point’s heading based on the Field orientation.

• acceleration – Returns the robot’s acceleration on a selected axis.

• gyro_rate – Returns the robot’s rotational speed on a selected axis.

• orientation – Returns the robot’s roll, pitch, or yaw orientation in degrees.

• quality – Returns the signal strength of the GPS Sensor.

• changed – Registers a function to be called whenever the GPS Sensor detects a change in heading.

Constructor – Manually initialize a GPS Sensor.

• Gps – Creates a GPS Sensor.

calibrate

calibrate calibrates the reference point, setting its configured heading as the current drivetrain heading. During this time, the robot must remain completely still as movement during calibration will produce inaccurate results.

Usage:
gps_sensor.calibrate()

Parameters	Description
	This method has no parameters.

set_origin

set_origin sets the position of the reference point on the robot manually. This can be done so to manually set a GPS Sensor’s location on a robot instead of doing so in the configuration settings.

Usage:
gps_sensor.set_origin(x, y, distance_units)

Parameters	Description
x	The x coordinate of the reference point on the robot.
y	The y coordinate of the reference point on the robot.
distance_units	The unit of measurement for the x and y coordinates: MM – millimeters INCHES

# GPS Sensor is mounted 25mm forward
# from the reference point on a robot

gps.set_origin(0, 25, MM)

set_location

set_location sets the position and heading of the reference point on the Field manually. This can be done to help reduce inaccuracies if the GPS Sensor is too close to the Field’s walls on startup to get a sufficient amount of the GPS Field Code in its view.

Usage:
gps_sensor.set_location(x, y, distance_units, heading, heading_units)

Parameters	Description
x	The x coordinate of the reference point on the Field.
y	The y coordinate of the reference point on the Field.
distance_units	The unit of measurement for the x and y coordinates: MM – millimeters INCHES
heading	The heading the reference point is facing relative to the absolute Field heading from 0 to 359.9 degrees.
heading_units	The unit of measurement for the heading: DEGREES

x_position

x_position returns the reference point’s x coordinate on the Field.

Usage:
gps_sensor.x_position(units)

Parameters	Description
unit	The unit of measurement: MM – millimeters INCHES

y_position

y_position returns the reference point’s y coordinate on the Field.

Usage:
gps_sensor.y_position(units)

Parameters	Description
unit	The unit of measurement: MM – millimeters INCHES

heading

heading returns the reference point’s heading based on the Field’s orientation from 0 to 359.9 degrees.

The heading corresponds to the absolute Field heading, which is a range of 0º to 359.9º in the clockwise direction. The 0º is in the 12 o’clock position.

Usage:
gps_sensor.heading()

Parameters	Description
	This method has no parameters.

acceleration

acceleration returns the robot’s acceleration on a specified axis from -4.0 to 4.0 Gs.

Usage:
gps_sensor.acceleration(axis)

Parameters	Description
axis	Which axis to use: AxisType.XAXIS AxisType.YAXIS AxisType.ZAXIS

gyro_rate

gyro_rate returns the robot’s rotational speed on a selected axis.

Usage:
gps_sensor.gyro_rate(axis, units)

Parameters	Description
axis	Which axis to use: AxisType.XAXIS AxisType.YAXIS AxisType.ZAXIS
units	The unit of measurement: VelocityUnits.DPS – degrees per second, from -1000 to 1000 VelocityUnits.RPM – revolutions per minute, from -167 to 167

orientation

orientation returns the robot’s roll, pitch, or yaw orientation in degrees.

Usage:
gps_sensor.orientation(axis, units)

Parameters	Description
axis	Which orientation to use: OrientationType.ROLL OrientationType.PITCH OrientationType.YAW
units	The unit of measurement: DEGREES

quality

quality returns the signal strength of the GPS Sensor as a percent.

Possible Values	Description
100	All reported positional and heading data from the GPS Sensor is valid.
~90	Any positional data is no longer being calculated by capturing information from the GPS Field Code, but rather through alternative means.
0 - 80	Only GPS Sensor heading values are valid, but as more time goes by where a GPS Sensor is not scanning enough of the GPS Field Code to accurately determine position and heading information, the reported signal quality will continue to drop until 0, where any GPS Sensor data is effectively frozen and no longer valid.

Usage:
gps_sensor.quality()

Parameters	Description
	This method has no parameters.

changed

changed registers a function to be called whenever the GPS Sensor detects a change in heading.

Usage:
gps_sensor.changed(callback, arg)

Parameters	Description
callback	A previously defined function that executes when the GPS Sensor’s heading changes.
arg	Optional. A tuple containing arguments to pass to the callback function. See Using Functions with Parameters for more information.

Constructor

Constructors are used to manually create Gps objects, which are necessary for configuring a GPS Sensor outside of VEXcode.

Gps

Gps creates a GPS Sensor.

Usage:
Gps(smartport)

Parameter	Description
smartport	The Smart Port that the GPS Sensor is connected to, written as Ports.PORTx where x is the number of the port.

# Create a GPS Sensor in Port 10
gps_sensor = Gps(Ports.PORT10)