{"id":56,"date":"2014-08-25T22:47:45","date_gmt":"2014-08-26T05:47:45","guid":{"rendered":"http:\/\/isaacsapple.littlebytesofpi.com\/Resources\/?page_id=56"},"modified":"2015-06-14T10:31:41","modified_gmt":"2015-06-14T17:31:41","slug":"understanding-sensor-measurements","status":"publish","type":"page","link":"https:\/\/isaacsapple.littlebytesofpi.com\/Resources\/understanding-sensor-measurements\/","title":{"rendered":"Understanding Sensor Measurements"},"content":{"rendered":"

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Measurement Axes<\/h1>\n

Many\u00a0devices, such as smart\u00a0phones and the Broadcom WICED Sense,\u00a0\u00a0have embedded\u00a0sensors that can measure acceleration, rotation, magnetic field, light, and other physical properties. Sensor measurements are given in a 3D coordinate system relative to the front, side, and top of the device. Both the iOS and the Android device use the same coordinate system: \u00a0the x,y axes are defined by the screen bottom and side, and the z axis comes directly out of the screen.<\/p>\n

\"acceleration_axes_2x\"
iOS Measurement Axes<\/figcaption><\/figure>\n
\"axis_device\"
Android Measurement Axes<\/figcaption><\/figure>\n

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Range and Resolution<\/h1>\n

A measuring device has a range and a resolution defining its capabilities and performance. \u00a0For example, if you had a yard stick with inch marks, the range of your measurements would be 3 feet, and the resolution would be one inch. This is useful for measuring longer objects, but is not very precise. \u00a0If you had a 30 cm ruler with millimeter marks, the range would be 300 mm, and the resolution would be 1 mm. This would be useful for measuring smaller things more precisely.<\/p>\n

The range and resolution of the sensors on your Android device is visible on the main screen of the Isaac\u2019s Apple Android application. \u00a0The range and resolution values are specified in the measurement units for that particular sensor.<\/p>\n

\"rangeResolution\"\u00a0 \u00a0 \u00a0\"rangeResolution2\"<\/a><\/p>\n

Consider the two accelerometers above. \u00a0The first sensor has a smaller resolution number. It is three times more precise than the accelerometer on the right. \u00a0The second accelerometer\u00a0has a larger range, it can measure plus or minus 4g while the accelerometer on the left can only measure plus or minus 2g.
\n<\/a><\/p>\n

Types of Android Sensors<\/h1>\n

The Isaac\u2019s Apple Android application can use any of the built in measurement sensors. \u00a0The main page of the Android application shows which sensors are built into your device.<\/p>\n

An Android device can have any of the following sensors.<\/p>\n

Accelerometer<\/h2>\n

Measures the acceleration force applied to the device , in meters per second per second (m\/s2). \u00a0This measurement includes the force of gravity which is always acting on the device. \u00a0For example, when the device is resting on a table, the accelerometer will be measuring 9.81 m\/s2, which is the Earth\u2019s gravitational pull.<\/p>\n

Gravity<\/h2>\n

Measures the force of gravity along the device axes in meters per second per second (m\/s2). \u00a0When the device is at rest, the gravity sensor will show the same measurement as the accelerometer.<\/p>\n

Linear Acceleration<\/h2>\n

Measures the acceleration force applied to the device, minus the force of gravity, in meters per second per second (m\/s2). \u00a0The linear acceleration measurement should be equivalent to the accelerometer measurement minus the gravity measurement. \u00a0The linear acceleration measurement is usually calculated by the device software, although it can be a unique hardware sensor in some high end Android devices.<\/p>\n

Gyroscope<\/h2>\n

Measures the rate of rotation around each of the axes in radians\/second (rad\/s). Rotation is positive in the counterclockwise direction.<\/p>\n

Orientation Sensor<\/h2>\n

Measures the orientation of the device in a familiar reference frame. The orientation sensor measurements values are:<\/p>\n