info: Nasa GPS Repeater- problem if wpt is over 100nm away

[roam]

if you have a Nasa GPS repeater, you may want to do a quick test on your unit.

We installed a new Nasa GPS repeater last year to replace an old one of another make. it is linked to a Garmin 152 GPS.
On a voyage earlier this year i put in the destination waypoint into the GPS some 350 nm distant. The speed on the Nasa repeater displayed a constantly changing number that did not correlate to our actual speed at all - it would change every 5-10 seconds with random values from 0.1 to 99. the GPS unit was unaffected. whilst under way, we decided to alter course slightly to avoid a potential hazard which happened to be less than 100nm away and hey presto, the speed returned to normal.

i reported this to Nasa who, after sending them video of the problem and a file of the nmea data agreed the unit needed some attention. they have kindly re-programmed the unit (although i am unable to test it until i return to the boat later this year).

They were reluctant to admit that it might affect other units. But it may....so you might want to check yours!

 

[pvb]

Nasa, innit?

 

[nigelmercier]

I imagine that they don't expect their instruments to last for such a long voyage.

 

[[70521]]

We installed a new Nasa GPS repeater last year to replace an old one of another make. it is linked to a Garmin 152 GPS.
On a voyage earlier this year i put in the destination waypoint into the GPS some 350 nm distant. The speed on the Nasa repeater displayed a constantly changing number that did not correlate to our actual speed at all - it would change every 5-10 seconds with random values from 0.1 to 99. the GPS unit was unaffected. whilst under way, we decided to alter course slightly to avoid a potential hazard which happened to be less than 100nm away and hey presto, the speed returned to normal.

i reported this to Nasa who, after sending them video of the problem and a file of the nmea data agreed the unit needed some attention. they have kindly re-programmed the unit (although i am unable to test it until i return to the boat later this year).

They were reluctant to admit that it might affect other units. But it may....so you might want to check yours!

Out of interest why would you want to set a WayPoint some 350nm away?

Sounds like cracking service, again, from NASA.

 

[roam]

errr.... because that was how far it was from origin to destination (Thailand to the Andamans in case you are interested).
cheers

 

[nimbusgb]

But does the instrument calculate great circle or rhumb line?

 

[macd]

But does the instrument calculate great circle or rhumb line?

It doesn't calculate anything. It's a repeater.

Roam: I had a NASA repeater on my last boat. Never showed the glitch yours seems to have had, even when nine years old.

 

[[70521]]

errr.... because that was how far it was from origin to destination (Thailand to the Andamans in case you are interested).
cheers

Ahh I understand now... thanks

We all do things differently never put in a WP until we are at close quarters to the hard stuff.

 

[demonboy]

We all do things differently never put in a WP until we are at close quarters to the hard stuff.

Are you saying you passage plan on the hoof? I hope I've misunderstood you.

When doing long crossings it is not unusual to be putting in WP many hundreds of miles away. On our last trip the distance between two points was over 800 miles, a straight run from the bottom of Sri Lanka to Sabang. Hence the need for an instrument that works over long distances.

 

[GHA]

Ahh I understand now... thanks

We all do things differently never put in a WP until we are at close quarters to the hard stuff.

It can be very useful long distance to display velocity made good, gaining half a knot by pointing away from your destination can get you there quicker. Though offshore I don't bother much keeping to rhum lines, keep the boat happy in the general direction. VMG is handy.

 

[roam]

hello macd: we had a Nasa repeater on our last boat too and if it had a similar fault, we didn't notice it, but we were mostly coastal sailing around the Med at the time. i rather suspect it may only be newer models.

if anyone has one, its worth testing this just by sticking in a waypoint of over 100 nm, even if you're not actually moving, it will show the fault.

 

[makingplansfor]

Definitely not a problem on my unit - sounds like a batch/firmware issue if they sorted it like that

 

[[70521]]

Are you saying you passage plan on the hoof? I hope I've misunderstood you.

When doing long crossings it is not unusual to be putting in WP many hundreds of miles away. On our last trip the distance between two points was over 800 miles, a straight run from the bottom of Sri Lanka to Sabang. Hence the need for an instrument that works over long distances.

No, not on the hoof, just don't see the value in placing a WP that far in the distance... (perhaps I do things the old way)

 

[GHA]

No, not on the hoof, just don't see the value in placing a WP that far in the distance... (perhaps I do things the old way)

One of the many fun bits about sailing is that you never stop learning new tricks

 

[[70521]]

One of the many fun bits about sailing is that you never stop learning new tricks

Very true

Mind you I am still coming to grips with this new Cardinal buoyage system