|
|
|
|
Precision
GPS Time Video Overlay Unit
|
|
| The GPSBOXSPRITE3 precision GPS time video overlay unit is designed to meet the needs
of people who require a precision time and date display combined with GPS position. This unit uses the precision
one pulse per second (1PPS) timebase from an integrated GPS receiver to drive its display. In addition to the display
of time and date, each video field is time stamped with the time in milliseconds since the last second. In this
way each video field can be easily referenced to the UTC time generated by the GPS receiver. |
|
|
|
|
| The video time inserter unit is housed in an ABS enclosure with phono connectors
for video in / out, a 2.1mm DC power socket and a latching power button. The GPS receiver's RS232 NMEA data is
available from a 3.5mm jack socket. A serial cable with a female DB9 connector is supplied to be used to connect
the unit to a PC. This allows the output of the integral receiver to be used to be with data logging or satellite
navigation software. Please note that the output is non standard 19200 baud, 8N1. The $GPRMC, $GPGGA and $GPVTG data sentences are transmitted. For USB only laptop PCs without a serial port order USBADAPT.
An active GPS antenna with a magnetic base and 3m cable is included with the unit. |
|
|
|
|
| Please note that the lead time
before dispatch of these units is approximately 5 - 10 working days. |
| Please read the FAQs. |
|
|
|
Other examples of science done using
the precision GPS time video overlay unit
|
Understanding the display |
| A camera's composite video signal is composed of a series of frames. Each frame is
made up of two fields which are interlaced when displayed. Each field is effectively the exposure snap shot made
by the camera. After a field has been exposed it is transmitted as part of the composite video signal. At the start
of the transmission of each field the camera generates a vertical synchronisation signal, VSYNC. The precision
time video overlay marks each field with the precise UTC time at which this signal occurs. This time is derived
from the 1PPS signal and NMEA data provided by the unit's GPS receiver. |
|
|
| The bottom line of the time display shows the time in milliseconds since the last
1PPS signal for each of the two fields in the frame. The odd field time is shown on the left, the even field time
on the right. The field time display from the time overlay unit is accurate to ±0.1ms over each second.
For individual fields the higher field time is the point at which the field began transmission from the camera.
The lower field time brackets the interval during which the camera exposure will have taken place. This display
allows you to read the UTC time of an event recorded on video from the screen and reference it to any other time
base very easily. Please note that not all video recording equipment will allow the display of individual fields
in playback. |
|
|
|
| 1 |
Latitude and Longitude (datum WGS84) |
| 2 |
Number of satellites in view, horizontal dilution of precision (HDOP) & altitude
in metres |
| 3 |
Speed over ground in kilometres per hour |
| 4 |
UTC time and date |
| 5 |
Time in milliseconds from the last 1PPS signal to the current frame / field VSYNC |
|
| The on screen display can be switched betwen 1, 2, 3 or 4 lines of data under the
control of the unit's select button. The date types which can be displayed are shown in the table above. The character
background can be toggled on and off. You cannot display any other combination of lines, change on which line each
data type is displayed or change the position of the display on the screen. The character size cannot be changed.
Once set, the user options remain stored in the unit until they are changed again. The unit has no other user controls. |
| Timing Accuracy and Suitability |
| The 1PPS signal from the GPS receiver is accurate to within 1 us as long as the receiver
has reported a valid and accurate fix for at least the previous 4 seconds. Under these conditions the time displayed
is accurate to ±0.1 milliseconds. Although the receiver will continue to output the 1PPS signal when its
position fix is lost, there is no specification of its performance when there is no position fix. Due to changes
in satellite configuration and signal reception all GPS receivers can produce invalid NMEA data or in some cases
fail to provide a 1PPS. In such cases the time displayed by the precision time overlay unit display will be incorrect
for as long as this error condition continues. Generally such errors cause the time display to halt and so can
easily be identified in any timing recording. Therefore any application must include an examination of the recorded
timings immediately prior to an event to ensure the event time is valid. The millisecond count over each second
allows the 1PPS second duration to be verified at the same time as the frame / field interval of the video signal
allows the millisecond count to be verified when any recording is reviewed. The precision time overlay is not suitable
if you need to simply read the time off the screen rather than reviewing a recording. Please ensure you are aware
of the limitations of the GPS system before ordering. |
| GPSBOXSPRITE2-U |
 |
Compatible with colour and mono composite video signals. 1Vp-p. PAL or NTSC* |
|
Dimensions 140 x 135 x 50mm LxWxH |
|
Power supply regulated 9 - 12V DC |
|
Power consumption 200mA maximum with antenna |
|
Operating Temp. 0° - 85°C |
| *By default the unit will be
supplied compatible with the video standard of the country from which you make your order. If you live in a PAL
country and require an NTSC compatible unit, or vice versa, then email and tell us this at the time you make your
order. |
|
| Integral GPS Receiver |
|
Ublox NEO-6M Chipset |
|
50 parallel channels |
|
Position Accuracy to 15m |
|
Datum WGS84 |
|
| |
| |
|
|
|
|
|
© The BlackBoxCameraTM Company Limited
2020
|
|
