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GPSBOXPLUS GPS Video Overlay Unit
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| From airborne surveys in Amazonia to fishery observation in Australia, there are a number of applications where
it is useful to display the information from a GPS receiver as a video text overlay. The GPSBOXPLUS GPS video overlay
unit provides a simple method for displaying GPS position data over a video camera’s composite video signal. The
data for the overlay is provided by an integral 20 channel GPS receiver. The GPS position data is also available
from the unit in standard NMEA 0183 RS232 serial data format. The unit will superimpose a display of latitude,
longitude, speed, heading, time, date and altitude onto any standard colour or mono composite video signal. A nine
character user defined string is also displayed. An active antenna is included with the unit. |
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| The screen display can be alternated between four lines of data, with or without a solid black background. Click
on each picture for larger version. |
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| The unit is housed in an aluminum enclosure with phono connectors for video in / out, a 2.1mm DC power socket and
an illuminated power button. RS232 NMEA serial data output is available from the female DB9 connector. This allows
the output of the integral receiver to be used to be with data logging or satellite navigation software. Display
options and the ID string are selected by two push buttons. The character background can be toggled on and off.
The altititude display can be toggled between feet and metres. The speed over ground display can be toggled between
knots, kilometres per hour or miles per hour. The date can be shown in either the standard DD/MM/YY format or the
North American MM/DD/YY format. The time is displayed according to a user selected timezone offset from the GPS
UTC time. You can select whether to display the data on either line 1 only, lines 1 & 2 only, lines 1,2, &
3 only, all four lines or have the screen clear. See the video clip above. 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. If you require a rearrangement of the standard data positions, please
contact us before you make your order and this can be programmed for you. |
| The table below summarises the data types and user selectable options displayed by the unit, with the NMEA data
sentence each is derived from. The GPGSA, GPGSV sentences may also be output from the device. |
| Data type |
Data sentence |
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Latitude |
$GPRMC |
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Longitude |
$GPRMC |
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Time ( User selected timezone offset ) |
$GPRMC |
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Date ( DD/MM/YY or MM/DD/YY format ) |
$GPRMC |
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Heading ( Track made good, degrees true ) |
$GPRMC |
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Speed over ground ( in knots, kph or mph* ) |
$GPRMC, $GPVTG |
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Altitude ( in metres or feet* above / below mean-sea-level (geoid) ) |
$GPGGA |
| *Calculated by the unit. Accurate to +/- 1. |
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| The NMEA serial data output from the GPSBOXPLUS unit can be used with satellite navigation or datalogging software.
As an example Google Earth *.kml track files can be generated from the raw data using
a converter like GPS visualizer. |
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| Suitability |
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| The GPSBOXPLUS unit is suitable for a wide range of visual survey tasks. However it should be noted that the standard
unit will not provide a continuously updated display when the unit is stationary or starts moving slowly, approximately
less than 3 mph. This means that the standard unit is not suitable for some applications, drifting with a slow
current while at sea for example. Even when a GPS receiver is stationary, each calculated position will be different
from the last. This would give the appearance of continuous random motion of the GPS receiver even when stationary.
The standard GPSBOXPLUS unit determines that it is in fact stationary based on pre-defined velocity and distance
values. If the vehicle’s velocity drops below a threshold value, then the position and heading are pinned to the
last computed value. The position and heading will remain at these values until the receiver detects that the velocity
has increased above a slightly higher threshold, or its position is computed to be more than a set distance from
that to which it is pinned. In a vehicle there are likely to be some effects such as delayed starting after a stop,
or occasional jumps in position when stopped among high buildings with severe multipath. Click on the image below
right for a video clip illustrating the effect. On request the GPSBOXPLUS unit can be supplied with this static
navigation option turned off. The overlay is updated once per second. Since the GPS receiver must calculate it's
position and then transmit it for display, the displayed data lags the actual motion by approximately two seconds. |
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Video Clip of static navigation at low speed <3mph
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| GPSBOXPLUS |
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Compatible with colour and mono composite video signals. 1Vp-p. PAL or NTSC |
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Dimensions 110 x 110 x 45mm LxWxH |
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Power supply required regulated 9 - 12V DC |
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Power consumption 150mA maximum with antenna |
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Operating Temp. 0° - 85°C |
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| Integral GPS Receiver GlobalSat ET-332* |
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SiRF StarIII high performance GPS Chip Set 20 channel all-in-view tracking |
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Very high sensitivity (Tracking Sensitivity: -159 dBm) |
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Rapid Time To First Fix at low signal level, Cold start average <40 seconds, Hot start average 1 second |
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WAAS & ENGOS supported |
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Position Accuracy 10 meters 2D RMS, 5 meters 2D RMS WAAS enabled |
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Datum WGS-84 |
| *Full GPS receiver specification. |
| GPS antenna specification |
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© The BlackBoxCameraTM Company Limited 2008
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