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GPS - Depth - Water Temperature

Keyboard Interface Video Overlay Units

The GPSBOXKBD-XDT GPS - Depth - Water Temperature video text overlay units provide a simple solution for displaying GPS data together with the data from a separate NMEA depth / water temperature sensor combined with a flexible text interface. The unit will superimpose a display of latitude, longitude, time, date, speed, heading, depth and water temperature onto any standard colour or mono composite video signal. Four lines of GPS NMEA data can be displayed combined with four lines of text which can be edited from a PS/2 compatible USB keyboard and positioned as a block on the screen. Two models are available. The GPSBOXKBDPLUS-XDT has an internal GPS receiver with an external antenna to provide the GPS data for the overlay. The GPSBOXKBD-XDT model is designed to be compatible with any external GPS receiver which sends data using the NMEA 0183 standard. Both units require a separate NMEA depth transducer as described below. For use with a combined GPS / depth transducer with a single NMEA serial output order GPSBOXKBD-DT. See our depth units compared for an overview of all three depth models.


No keyboard is included. Order the FLEXKYBD item for use with these units.

GPS types

The GPSBOXKBD-XDT unit can be used with any GPS receiver with NMEA 0183 RS232 serial output. 4800 baud 8N1.

The units are housed in an aluminum enclosure with phono connectors for video in / out, a 2.1mm DC power socket and a power switch. Keyboard connection is via a USB A socket for a PS/2 compatible USB keyboard. These units will only work with standard USB keyboards which implement PS/2 functionality. They will not work with USB only keyboards which require PC operating system support. The external GPS receiver's PC connection cable goes into the GPSBOXKBD-XDT's upper male DB9 connector.


The GPSBOXKBD-XDT unit is designed to be used to display depth / water temperature for marine survey applications.

The data position on each line is fixed, but each line can be moved to any line location on the screen or hidden dependent on the user requirement. The speed over ground display can be switched between knots and kilometres per hour. The character background can be toggled on and off. 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 +/- 12 hour timezone offset from the GPS UTC time. The character size cannot be changed by the user, although there are two alternate character sets to the standard which can be selected at the time you make your order. Please contact us before you make your order for details. The gps data display configuration cannot be changed. The depth is displayed in metres. The water temperature is displayed in degrees centigrade.
The table below summarises the data types and user selectable options displayed by the unit, with the NMEA data sentence each is derived from. If you are unfamiliar with the serial output of the GPS receiver you intend to use with the GPSBOXKBD-XDT unit you should connect it to a PC and use hyperterminal to check that the XXRMC and XXVTG data sentences are transmitted. If they are not refer to the documentation from your receiver's manufacturer for the method required to enable NMEA output. Data sentences other than XXRMC and XXVTG should be turned off.
Data type Data sentence required
Latitude $XXRMC
Longitude $XXRMC
Time ( User selected timezone offset ) $XXRMC
Date ( DD/MM/YY or MM/DD/YY format ) $XXRMC
Heading ( Track made good, degrees true ) $XXRMC
Speed over ground ( in knots or kph ) $XXRMC, $XXVTG
Depth ( in metres ) $XXDBS, $XXDBT, or $XXDPT. See below
Temperature ( in degrees centigrade ) $XXMTW


GPSBOXKBD-XDT video overlay unit documentation
document GPSBOXKBD-XDT short form command table

Depth Data Sentences
The lower male DB9 socket of the GPSBOXKBD-XDT, labelled AUX, is the separate RS232 serial input for an NMEA depth / water temperature sensor. The unit can read one of three different NMEA depth data sentences, XXDBS, XXDBT or XXDPT. Some devices will transmit all three, but many will only have one or two. Please check the manual for your device, and if possible, confirm its serial output using hyperterminal to see which sentence(s) are available in your case. The GPSBOXKBD-XDT unit will default to display the depth from the $XXDBS if this is present. The other depth data sentences will be ignored if they are present. If $XXDBS is not present then the depth from $XXDBT will be displayed if this is present, otherwise $XXDPT would be displayed.
Each of the data sentences reports the depth in a slightly different way. Therefore it is important to know which data sentence(s) are generated by your depth sensor and which is used for display. The table below summarises the NMEA sentences which can be read and the data from each that will be displayed by GPSBOXKBD-XDT in order of precedence for display. Please note that the XXDPT sentence reports the depth as two figures, a combination of the depth measured and an offset, either positive or negative, that you may be able to enter into the receiver or sensor. This allows adjustment of the measured depth to either the keel or waterline as required. The GPSBOXKBD-XDT unit ignores this offset. The depth reported in feet and fathoms is also ignored. The depth can only be displayed in metres.
Depth data sentence Depth displayed as:
$XXDBS,35.4,f,10.8,M,5.9,F Depth below surface in metres. ( feet and fathoms ignored )
$XXDBT,25.5,f,7.8,M,4.2,F Depth below transducer in metres. ( feet and fathoms ignored )
$XXDPT,7.8,3.0 Depth below transducer in metres. ( offset in metres ignored )
The GPSBOXKBDPLUS-XDT unit is suitable for a wide range of waterborne visual survey tasks. However it should be understood that the unit will not always provide a continuously stationary display when the unit is stationary. Even when a GPS receiver is stationary each calculated position can be different from the last due to the sources of error in the GPS system which limit positional accuracy. These errors will give the appearance of random motion of the GPS receiver when stationary or occasional jumps in speed when stopped. Therefore if you will be operating at very low speeds below 0.5 knots you should use GPSBOXKBD-XDT with an appropriate external GPS receiver.


Please ensure you are aware of the limitations of the GPS system before ordering.

Four lines of 26 characters, font and character size fixed
UK English or US / International English keyboard mapping available*
Compatible with colour and mono composite video signals. 1Vp-p. PAL or NTSC
Dimensions 110 x 110 x 45mm LxWxH
Power supply required 9 - 12V DC
Power consumption 50mA (without keyboard)
Operating Temp. 0° - 85°C
*All units are shipped with US / International English keyboard mapping unless ordered from the UK.
GPSBOXKBDPLUS+XDT GPS Receiver with external Antenna*
High performance MTK GPS chipset
Very high sensitivity (Tracking Sensitivity: -165 dBm)
Rapid Time To First Fix at low signal level, Cold start average 41 seconds, Hot start average 1 second
WAAS & ENGOS supported
Position Accuracy 10 meters 2D RMS, 5 meters 2D RMS WAAS enabled
Datum WGS-84
* GPS antenna specification
The GPSBOXKBD-XDT is designed to be used with separate GPS and depth sensors. However if you require the flexibility to also use the unit with devices which produce a single combined GPS and depth serial data output you can order the DUALDB9 adaptor. This allows a single RS232 data stream which includes both NMEA GPS and depth data sentences to be split between the two inputs of the GPSBOXKBD-XDT.

Mounting Brackets for GPSBOXKBD units.

The GPSBOXKBD units can be used in a wide variety of systems and no one power supply solution would be suitable for them all. Therefore the unit does not include a power supply as standard. You may already have a suitable power supply or you may wish to source this requirement locally. Otherwise UK customers should order the PWRSUP item. This item is not available to customers outside the UK.

All the GPSBOXKBD units can be supplied with BNC connectors on request. If you want this option then make your order in the normal way, then just email us quoting your order number: sales@pic-osd.com

At the time you make your order we can provide one of two alternate character sets to the default standard character set. The character set cannot be changed by the user once units are delivered. The standard character set is suitable for a wide range of applications including those where small screens are used or viewed at a distance. The smaller alternate character sets can be more suitable for use with LCD panel displays.




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