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Precision GPS Time Video Overlay Unit

Frequently Asked Questions


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


GPSBOXSPRITE documentation

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.
Q. General questions about setup and compatibility etc.
A. Please see Bruce Berger's excellent blog post about his setup for an example.

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.

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.
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.



The current version of the GPSBOXSPRITE3-U is not affected as it uses a different GPS receiver.

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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