V-Data VED-M Operation Manual

693 Melrose Road
Lottsburg, VA 2251
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Video Encoder/Decoder Model VED-M

Operation Manual

Description

The Video Encoder/Decoder (VED) Model VED-M has two modes of operation, encode
and decode. When GPS data from an external GPS receiver is available, the VED automatically
enters the encode mode. In encode mode GPS data is inserted into camera video in both alpha­numeric and edge-code format. The edge-code data consists of one bit per video line placed
immediately after horizontal sync. Edge-code data appears at the far left of the screen in a video
monitor capable of underscan. The edge-code is not visible in normal scan. When video
containing edge-code is input, the VED automatically enters the decode mode. In decode mode
the edge-code is read and GPS data is output in simulation of a GPS receiver.

Applications

The VED with video camera and video cassette recorder (VCR) comprise a complete
GPS data acquisition and retrieval system. In the encode mode imagery and GPS data are stored
together on convenient video tape. In the decode mode GPS data is recovered from the playback
video and output in a form compatible with popular moving map programs, thereby allowing
simultaneous viewing of camera picture and map location. Since complete GPS data is stored on
each video field, the VED will output GPS data even when the VCR is paused, or when the input
is a captured video image. For fleet vehicle identification, the VED serial number is included in
the on-screen display. A rotary switch allows GMT or UTC time to be offset to local time. The
hour offset is also displayed to maintain a link to UTC time. Internal switches allow for top or
bottom screen display, and selection of English or metric units.

Power

The VED operates at 100 milliamps with nominal 12 VDC (9-16 VDC) input power.
Input power up to 30 VDC can be used provided that the installation allows for dissipation of 3
watts of heat from the VED enclosure. The power input connector is a 2.1 mm jack with long
barrel to allow use of locking plugs. The center pin is positive and reverse polarity protection is
built-in. Input power is routed through a polycrystalline self-resetting fuse inside the VED to
several pins on the COM connector to provide power to the GPS receiver and other sensors. It is
recommended that the power source be fused at 1 amp for additional protection. Note: Some 2.1
mm plugs do not have recessed center pins. Avoid use of these plugs. If the center pin contacts
the barrel of the jack during insertion, a short circuit will occur.

2

Encode Mode

On power-up the VED begins searching for either GPS input or edge-coded video input
to determine whether to enter encode or decode mode. If GPS data is detected the VED enters
the encode mode and begins inserting alpha-numeric data and edge-code data into the video.
Once the encode mode is entered, removal of GPS input will cause the warning "NO GPS IN" to
be displayed. If GPS input is present but the receiver is not tracking, the warning
"ACQUIRING" will be displayed. If neither warning is displayed, the GPS data is valid.

As a minimum, the VED requires the $GPRMC message in RS-232 form (4800 baud, 8
data bits, 1 stop bit, no parity) to be input from an external GPS receiver. If the $GPGGA
message is also present, receiver status and altitude will be added to the display. If a pulse-per­second is available from the GPS receiver, precision time will be displayed to the millisecond,
otherwise time will be displayed to the second. When millisecond time is displayed, it is
sampled at vertical sync and updated on each video field.

Assuming that the $GPRMC and $GPGGA messages are input and the receiver is
tracking, the display will be as follows:

Bottom line from left; serial number, latitude, longitude, speed, course.
Top line from left; date, time, hour offset, receiver status, altitude.

The receiver status consists of the number of satellites separated by a "/" or a "*" from the
horizontal dilution of precision (HDOP). If more than 9 satellites are tracked the number of
satellites tracked remains at 9. A "/" indicates normal track, and a "*" indicates differential
track. The HDOP ranges from 00 to 99 and is an indication of the quality of the position fix
based on geometry. Smaller numbers indicate higher quality, with 00 or 01 being excellent.

To access the internal switches and adjustment, disconnect power and remove the two
screws from the rear connector panel. Slide the rear connector panel and attached board out a
few inches to gain access to the switches. The potentiometer adjustment is factory set and
determines the width of the lines of displayed data. Adjustment is correct when the lower line is
fully visible and centered horizontally on the video monitor in normal scan. The four internal
switches control display options as follows:

Switch 1 determines the polarity of the hour offset. In the on position, hour offsets of -12 to 0 to
+3 are obtained by using the rotary switch. In the off position, hour offsets of 12 to 0 to -3 are
obtained.
Switch 2 in the on position displays data at the bottom of the video picture. In the off position
data is displayed at the top of the picture.
Switch 3 in the on position displays altitude in feet. In the off position altitude display is in
meters.
Switch 4 in the on position displays speed in MPH if switch 3 is on, and Km/H if switch 3 is off.
In the off position speed is displayed in knots regardless of the position of switch 3.