"Street View auto ready" specifications

Street View auto ready badge

Introduction

These specs detail all hardware, timing, and data requirements for advanced, vehicle/bike-mountable 360 cameras that intend to offer high-speed, high-accuracy Street View capture and publishing capabilities. These cameras can be controlled via the Street View app.

Imagery

  • ≥15MP at ≥5FPS
  • 360º horizontal FOV
  • ≥135º contiguous vertical FOV—if less than 180º vertical FOV is captured, the FOV must at least cover the zenith
  • Google will review image and geometry quality

IMU

Recommended components:


The accelerometer should satisfy the following specifications:

  • Resolution: ≥16 bit
  • Range: ≥ +/- 8G with ≥4096 LSB/g typically
  • Sampling rate: ≥200 Hz with <1% jitter
  • Low-pass filtering must be enabled to eliminate aliasing. The cut-off frequency should be set at the highest possible value below the Nyquist frequency, which is half the sampling rate. For example, if the frequency is 200 Hz, then the low-pass filter cut off should be below 100 Hz but as close as possible.
  • Noise Density must be ≤300 μg/√Hz, and should be ≤150 μg/√Hz
  • Stationary noise bias stability <15 μg * √Hz from 24-hour static dataset
  • Bias change vs. temperature: ≤ +/- 1mg / °C
  • Best-fit line non-linearity: ≤0.5%
  • Sensitivity change vs. temperature ≤0.03%/°C

The gyroscope should satisfy the following specifications:

  • Resolution: ≥16 bit
  • Range: ≥ +/- 1000 deg/s with ≥32 LSB/dps
  • Sampling rate: ≥200 Hz with <1% jitter
  • Low-pass filtering must be enabled to eliminate aliasing. The cut-off frequency should be set at the highest possible value below the Nyquist frequency, which is half the sampling rate. For example, if the sampling frequency is 200 Hz, then the low-pass filter cut off should be below 100 Hz but as close as possible.
  • Noise Density: ≤0.01 °/s/√Hz
  • Stationary Bias Stability <0.0002 °/s *√Hz from 24-hour static dataset
  • Bias change vs. temperature: ≤ +/- 0.015 °/ s / °C
  • Best-fit line non-linearity must be ≤0.2%, should be ≤0.1%
  • Sensitivity change vs. temperature: ≤0.02% / °C

The magnetometer should satisfy the following specifications:

  • Resolution: ≤0.3 μT
  • Range: ≥ +/- 1000 μT in x,y and ≥ +/- 2000 μT in z
  • Sampling rate: ≥10 Hz with <1% jitter
  • Best-fit line non-linearity should be ≤1%
  • Sensitivity change vs. temperature: ≤0.01% / °C

GPS

Recommended components:

  • Either of the u-blox MAX-M8 series or the u-blox NEO-M8 series

Requirements:

  • Sampling rate: ≥4 Hz
  • Constellation: simultaneous tracking of at least GPS and GLONASS
  • Time to first fix:
    • Cold: ≤40 seconds
    • Hot: ≤5 seconds
  • Sensitivity:
    • Tracking: -158 dBm
    • Acquisition: -145 dBm
  • Horizontal position accuracy: 2.5 meters (circular error probable (CEP), 50%, 24 hours static >6 SVs)
  • Velocity accuracy: 0.06 m/s (50% at 30 m/s)
  • Operational limit: ≥4g
  • Internal antenna or rigidly affixed external antenna of known type

Antenna design:

Physically small products, such as cameras that contain both the GPS receiver system and numerous complex electronic systems, are prone to problems with radio receiver performance caused by RF emissions from the included electronics systems. This interference is often in-band to the radio receiver and as such, cannot be filtered out. Given this, we have specified a set of tests to verify the device is working properly in the GPS Testing section below.

Camera architecture

The six degrees of freedom (6-DOF) transformation (relative position and orientation) between each sensor’s and each camera’s frame of reference (FOR) must be specified with respect to the accelerometer FOR. The sensor FOR must be as defined in the sensor’s data sheet and aligned with the sensor’s physical placement in the device. The FOR for each camera has the positive z-axis pointing away from the device into the FOV of the camera along the optical axis, the x-axis points to the right, the y-axis points down from top to bottom, and the origin of the FOR is at the camera’s optical center. The GPS FOR is located at the antenna.

The 6-DOF transformation (3-DOF for position and 3-DOF for orientation) of each sensor or camera is represented as a 3x4 transformation matrix T = [R p], where R is the 3x3 rotation matrix representing the orientation of the sensor or camera FOR in the accelerometer FOR, and p is the 3x1 position vector (x, y, z) in meters representing the origin of the sensor or camera FOR in the accelerometer FOR.

The requested transformations can be from a computer-aided design (CAD) model of the device and do not need to be device-specific to account for manufacturing variations.

Miscellaneous

Connectivity:


Power (either or both of the following models should be employed):

  • USB 3.1 tethered power and recharging, supporting ≥ 4 hours of recording
  • Battery-powered operation supporting >1 hour recording and upload

Mechanical, Environmental:

  • IP67 or IP68 rating or compatible with a water- and dust-proof accessory case that minimally affects image
  • Ambient Temperature: 0˚ to 40˚C operating, -20˚ to 60˚C storage
  • Shock: 0.5 meter drop. 1 meter drop shipping - while packaged
  • Vibration: 3 gRMS (Shipping - while packaged)
  • Humidity: 90% operational




Timing specifications

All sensor measurements must be accurately timestamped with respect to the same stable system clock. The measurements must be timestamped when the sensor measured the quantity, not when the processor received the message from the sensor chip. The timestamp jitter between the different sensor readings should be <1 ms. All timestamps recorded in the same sensor data log must be continuous with no discontinuities. If the hardware reboots or resets and the system clock resets, then a new log must be created to store the new incoming data.


GPS

The GPS sensor should support an output of a time pulse and an associated message with the GPS time corresponding with the time pulse. This can be used to timestamp other GPS data packets with the same GPS epoch timestamp. The device should have an input to receive these time pulses, and when it receives a leading or trailing edge (whichever is appropriate), it should record the timestamp from the stable system clock. When the corresponding message packet is received that contains the GPS time, the device can now calculate the timestamp with respect to the stable system clock when it receives the navigation message from the GPS sensor, which contains the GPS time.


Video / images

The image sensor must support hardware timing to determine the precise time with respect to the stable system clock. In the event of dropped frames, subsequent frames must still reflect accurate timestamps. The timestamp must be with respect to the first active photon in the image. The manufacturer must specify which pixel this corresponds to.


IMU / magnetometer

The IMU (accelerometer and gyroscope) and magnetometer measurements must be timestamped with respect to when the measurement was taken, not when received.





Data specifications

Street View optimized cameras and systems must collect multiple, per-sensor data measurements per second. The following details the data for each individual measurement.


IMU and magnetometer data requirements

IMU (accelerometer and gyroscope) measurement data:

int64 time_accel;    // The time in nanoseconds when the accelerometer
                     // measurement was taken. This is from the same stable
                     // system clock that is used to timestamp the GPS and
                     // image measurements.
// The accelerometer readings in meters/sec^2. The x, y, z refer to axes of
// the sensor.
float accel_x;
float accel_y;
float accel_z;

int64 time_gyro;     // The time in nanoseconds when the gyroscope
                     // measurement was taken. This is from the same stable
                     // system clock that is used to timestamp the GPS and
                     // image measurements.
// The gyro readings in radians/sec. The x, y, z refer to axes of the sensor.
float gyro_x;
float gyro_y;
float gyro_z;

Magnetometer data:

int64 time_mag;  // The time in nanoseconds when the magnetometer
                 // measurement was taken. This is from the same stable
                 // system clock that is used to timestamp the GPS and
                 // image measurements.

// Magnetic field components in microtesla (uT). The x, y, z refer to the axes
// of the sensor.
float field_x;
float field_y;
float field_z;

GPS data requirements:

int64 time;         // Time in nanoseconds, representing when the GPS
                    // measurement was taken, based on the same stable
                    // system clock that issues timestamps to the IMU
                    // and image measurements
double time_gps_epoch;      // Seconds from GPS epoch when measurement was taken
int gps_fix_type;           // The GPS fix type
                            // 0: no fix
                            // 2: 2D fix
                            // 3: 3D fix
double latitude;            // Latitude in degrees
double longitude;           // Longitude in degrees
float altitude;             // Height above the WGS-84 ellipsoid in meters
float horizontal_accuracy;  // Horizontal (lat/long) accuracy in meters
float vertical_accuracy;    // Vertical (altitude) accuracy in meters
float velocity_east;        // Velocity in the east direction represented in
                            // meters/second
float velocity_north;       // Velocity in the north direction represented in
                            // meters/second
float velocity_up;          // Velocity in the up direction represented in
                            // meters/second
float speed_accuracy;       // Speed accuracy represented in meters/second

Video:

Video must be recorded at a frame rate of 5 Hz or greater. To reduce the file size, the data recorded from the camera should be compressed using HEVC / H.265 encoding. The camera should also record metadata associated with each image frame. For each image,

int64 time;   // The time in nanoseconds when the image was taken.
              // This is from the same stable system clock that is used to
              // timestamp the IMU and GPS measurements.

// The corresponding frame in the video.
int32 frame_num;

The time must be from the first active photon in the image and the manufacturer must specify which pixel this corresponds to. Manufacturer partners must also provide the rolling shutter details in order to calculate the time each pixel was exposed.


API support

Wi-Fi-enabled 360 cameras must support the control of basic camera operations via the Open Spherical Camera (OSC) API and/or direct content upload via the Street View Publish API. Support for OSC API control over USB 3.1 connections is optional but not required.





GPS testing

It’s very easy to have performance limitations due to noise, antenna selection, antenna implementation, LNA, filter, and transmission line implementation. This section defines a test process to ensure that your final product (as a whole) meets the performance requirements needed to ensure accurate data output and qualify for Street View auto ready certification.


Certification service

To simplify the testing of the devices, we have worked with Taoglas Antenna Solutions to provide a Google Street View Qualification GPS RF Service. Taoglas Antenna Solutions are leading experts in GPS technology with 5 Anechoic Test Chambers and all necessary equipment to perform the following tests. However, any comparable service provider can be engaged to perform the following tests.


Test setup

Testing must be done in a 3D anechoic chamber. This chamber shall conform to the range requirements and test site characteristics of the CTIA Over-the-Air Wireless Device Test Plan [1] sections 3 and 4 for the GPS L1/CA frequency, 1575.42 MHz except when in conflict with other requirements below.

The device shall provide a means to report NMEA GPS result strings [2] to an external computer for evaluation of the GPS status. This is required and testing is not possible otherwise.

The measurement/transmit antenna in the chamber shall be right-hand circular polarization (RHCP) with an axial ratio of 1 dB or better.

The GPS signal generator shall replicate one GPS satellite L1/CA signal.

Signal strengths mentioned in the following test processes are defined to have an accuracy of +/- 1 dB with an offset of 3 dB as measured at the device-under-test (DUT) position with a dipole centered on the measurement frequency. For example, when the test calls for -120 dBm, the chamber calibration shall show the measured power at the DUT location to be -117 dBm +/-1 dB. The 3 dB offset is to account for the calibration antenna being a linearly polarized dipole.

Test data points shall cover a hemisphere most representative of the device’s typical use-case. Manufacturers should try to maximize the coverage of the antenna to support a wide range of users’ usage.


Pass/fail determination

The following Acquisition and Tracking Conformance tests are required for a pass/fail determination. These tests are run only for the GPS L1/CA signal.

After values that do not change for a given sample of DUT—such as Data Point Dwell Time (DPDT) or Required Acquisition Signal Quality (RASQ)—are determined, these values can be re-used for a specific DUT sample in later tests to save test time as long as the DUT sample is not modified in any way.


Acquisition conformance test procedure

This is a single point offset test to provide a quick pass/fail answer. The DUT is positioned with the measurement perpendicular to the base plane of the measurement hemisphere, that is, at theta = 0° or zenith.

An incident signal equivalent to -120 dBm shall be presented and the DUT triggered to begin a cold start.

After the DUT has acquired the test signal, as seen by examining the GPGSV message [2], the test signal shall be turned off and the duration required for the GPGSV signal to reflect the loss of signal recorded. This duration, plus 3 seconds, shall be defined as the Data Point Dwell Time or DPDT.

The test signal power shall be set to the DUT’s conducted acquisition sensitivity level. When in doubt, use the level stated in the receiver datasheet. {The DUT shall be commanded to cold start, and after 45 seconds the GPGSV string is evaluated to determine if the receiver has acquired the test signal. If the signal is not acquired, the test signal shall be increased 1 dB.} The previous section in brackets {} shall be repeated until the test signal is acquired.

After the test signal level that allows the DUT to acquire is determined, the GPGSV string shall be evaluated over 10 seconds and the satellite signal quality value as reported by the DUT recorded. These 10 values are then averaged and defined as the Required Acquisition Signal Quality or RASQ.

The test signal strength shall then be set to -138dBm and the DUT allowed to acquire. The test signal strength is then held constant for the remainder of the test.

At each 15° increment over the selected hemisphere, the receiver shall be held stationary for the DPDT duration. At the end of this period, the GPS NMEA string GPGSV shall be examined. For the data point to pass, the satellite signal quality value as reported by the DUT must be equal or higher than the previously recorded RASQ value.

All data points must pass to pass the test.


Tracking conformance test procedure

This is a single point offset test to provide a quick pass/fail answer. The DUT is positioned with the measurement perpendicular to the base plane of the measurement hemisphere, that is, at theta = 0° (zenith).

An incident signal equivalent to -120 dBm shall be presented and the DUT triggered to begin a cold start.

After the DUT has acquired the test signal as seen by examining the GPGSV message [2], the test signal shall be turned off and the duration required for the GPGSV signal to reflect the loss of signal recorded. This duration plus 3 seconds shall be defined as the Data Point Dwell Time or DPDT.

The test signal shall be restored and the DUT allowed to acquire the satellite.

The incident test signal shall be lowered to -151 dBm.

At each 15° increment over the selected hemisphere, the receiver shall be held stationary for the DPDT duration. At the end of this period, the GPS NMEA string GPGSV shall be examined to determine if the test signal is still being seen by the receiver and the results recorded for that data point.

All data points must pass to pass the test.


References

[1] CTIA, "www.ctia.org," June 2016: http://www.ctia.org/initiatives/certification/certification-test-plans

[2] National Marine Electronics Association, "NMEA Standard 0183," 2008





Exceptions

Exceptions may be granted for specific hardware and software solutions that do not match individual requirements but meet the overall end-to-end performance metrics stipulated in this document.





Product evaluation

When you’re ready to submit a compatible product for certification review—or if you have questions in the meantime—contact us.