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Precision GPS Time Video
Overlay Unit
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Frequently Asked Questions
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GPSBOXSPRITE3
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| On this page we try to answer some of the questions most frequently asked about the
precision GPS time video overlay unit. If you have a question about the product after reading the documentation
or if you require any further information please contact us: sales@pic-osd.com |
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| Q. Questions about supposed
GPS errors and error correction, effect on timing accuracy, etc. |
| A. Please read the GPSBOXSPRITE3
documentation.
This explains how the unit reacts to GPS error conditions. Thanks to the excellent error analysis of Oliver
Kloes and others there is good understanding of these conditions. None
of the errors are systematic or long lasting, less than 0.02 % of all timings. They are random, of short
duration and can easily be detected from the unit's display. The GPSBOXSPRITE3 unit does not maintain its own clock
and is therefore is not susceptible to errors at any single point in time. The time displayed is based on the continuous
update of the data received from the GPS receiver and the 1PPS signal. Because the display is continuously updated,
any random error in the data will be corrected by subsequent updates. The 1PPS signal, frame time interval, millisecond
counter and NMEA serial data provide 4 independent timing references which allow errors to be detected when they
do occur. |
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| Q. General questions about setup
and compatibility etc. |
| A. Please see Bruce Berger's
excellent blog post about
his setup for an example. |
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| Q. Questions about either the
old STVASTRO, GPSBOXSPRITE or GPSBOXSPRITE2 units, sold pre-2011, showing the incorrect date. |
| A. Please note this error does
not affect either our current GPSBOXSPRITE3-U units or GPSBOXSPRITE2-U units sold since 2011. In October - November
2014 three users of our STVASTRO, GPSBOXSPRITE and GPSBOXSPRITE2 units reported the same error in which the date
displayed by the video overlay was incorrect. Apart from the date, all the other information displayed, position,
time and altitude was apparently correct. Thanks to user Jose Madiedo this problem was rapidly diagnosed as a fault
in the memory of the Garmin GPS-35 receiver antenna units used with his STVASTRO units. It was found that this
problem could initially be cleared by reseting the device using the Garmin sensor configuration utility SNSRCFG.
However it was found that this fix did not stop the error recurring. We threfore regret that there is no fix possible
for the error. |
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The date problem is caused by the non-volatile memory of the Garmin GPS receiver
and is related to the GPS 1024 week rollover error. It is nothing to do with the STVASTRO or GPSBOXSPRITE video
overlay electronics so we cannot provide a general guaranteed fix to everyone who may have this type of problem.
If you have any questions about any of the information presented on this page please contact us directly sales@pic-osd.com. If you have questions
about the nature of the error please contact Garmin technical support via the Garmin website.
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| The incorrect date problem affects the Garmin GPS-35 combined antenna receiver and
the Garmin GPS-25 receiver module. Both of these receivers use the same chipset. It is believed that the error
occurs due to an incorrect setting in the non-volatile memory of the receiver after a GPS euphemeris update related
to the 1024 week rollover. The GPS-35 is used with the STVASTRO unit we sold from 2001. The GPS-25 was included
in the GPSBOXSPRITE and GPSBOXSPRITE2 units we sold from between 2009 and 2011. |
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GPS35 with STVASTRO
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GPSBOXSPRITE
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| The current version of the GPSBOXSPRITE3-U is not affected as it uses a different
GPS receiver. |
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| Q. How many GPSBOXSPRITE3 do
you have left? How long do you think they will last before you sell out? Can I still purchase a GPSBOXSPRITE3 unit?
Etc. |
| A. We build the GPSBOXSPRITE3-U
units in batches. Between batches we may temporarily run out of stock. We do not provide a running countdown for
the stock of the GPSBOXSPRITE3-U. Stock is available when the item is shown on the products page. If you wish to
make an order you should do so. We will make it clear on our website when the units are not available. |
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© The BlackBoxCameraTM Company Limited
2020
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