Difference between revisions of "Event logger"

Revision as of 10:25, 23 April 2013

Features

• ~1 micro second precision
• Up to 4 source channels:
  • IMU
  • GPS
  • Image Acquisition
  • External General Purpose Input (e.g., odometer - 3..5V pulses)

Description

The FPGA-based Event Logger uses local clock for time-stamping, so each log entry (IMU, GPS, Image Acquisition and External Input) is recorded with timing info.

In a single camera each acquired image has a timestamp in its header (Exif). The log entry for images has this timestamp recorded at the logger (local) time.

Multiple cameras (e.g., Eyesis4π) are synchronized by the master camera to sub-microsecond, and each acquired also image has the master timestamp in Exif. The log entries for images (if logged in the camera other than master so with different local clock) have 2 fields - master timestamp (same as in image Exif) and local timestamp (same clock as used for IMU), so it is easy to match images with inertial data.

A typical log record has the following format:

[LocalTimeStamp] [SensorData]
Examples or parsed records:
[LocalTimeStamp]: IMU: [wX] [wY] [wZ]  [dAngleX] [dAngleY] [dAngleZ] [accelX] [accelY] [accelZ] [veloX] [veloY] [veloZ] [temperature]
[LocalTimeStamp]: GPS: [NMEA sentence]
[LocalTimeStamp]: SRC: [MasterTimeStamp]

Notes

• GPS data is written to both, the event log and the image header (Exif).
• IMU data is written only to the event log.
• Example IMU (ADIS16375) samples rate is 2460Hz.
• Example GPS receiver (Garmin 18x serial) samples rate is 5Hz in NMEA or other configured format.

Examples

Raw

Raw *.log files are found here

Parsed

parsed_log_example.txt (41.3MB) - here

Tools for parsing logs

Download one of the raw logs.

• PHP: Download read_imu_log.php_txt, rename it to *.php and run on a PC with PHP installed.
• Java: Download IMUDataProcessing project for Eclipse.