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Precision GPS Time Video Overlay Unit
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| Recently space.com and some other news sites ran a stories on an Israeli science team's investigation into the
relationship between sprites and UFO sightings and Kevin Fetter's observation of the secretive X-37B robotic space
plane. Images and video that accompanied these stories was annotated with the precise UTC time by a precision GPS
time video overlay unit which we sold several years ago. . |
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| As a result we have had several enquiries about the unit and whether it was still available. The original model
was discontinued in 2004. However we have an updated version which is available now. Basically these have the same
electronics with an integrated GPS receiver to greatly simplify the setup and operation of the unit. Please note
that there are some cosmetic imperfections on these units and so they are sold at a discount to reflect this.w |
| The lead time before dispatch of these units is approximately 5 - 10 working days. |
| Please read the FAQs. |
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GPSBOXSPRITE2
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| The GPSBOXSPRITE2 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 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 2m cable is included with the unit. |
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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. |
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| 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. |
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| 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 |
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| 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 |
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Compatible with colour and mono composite video signals. 1Vp-p. PAL or NTSC* |
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Dimensions 140 x 135 x 50mm LxWxH |
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Power supply regulated 9 - 12V DC |
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Power consumption 200mA maximum with antenna |
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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. |
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| Integral GPS Receiver |
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Ublox RCB-LJ |
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16 parallel channels |
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Position Accuracy to 15m |
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Datum WGS84 |
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© The BlackBoxCameraTM Company Limited 2011
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