Northstar 951 XD in Loran Mode (accuracy?) - The Hull Truth

jlr · 05-25-2004, 07:36 AM

I have a Northstar 951 XD. It says and I believe it to be accurate to about 9' 95% of the time in DGPS mode. First question--without adding a Loran antenna , can I display TD's rather than Lat/Lon. If so, will the TD's also be accurate to about 9' or so? I have a set of TD numbers (fishing spots) and I want to be able to locate them accurately with this GPS. What's the best way to do this without converting them to Lat/Lon?

Kerry · 05-25-2004, 07:29 PM

Many units (not being specific Loran units) can display/input TD's BUT any conversion will only be approximate within the accuracy of TD & Lat/Long conversions, which isn't all that flash and certainly one shouldn't be expecting that converted TD's to LAt/Long to be anywhere close.

Best way is to find with actual Loran and save with GPS or convert and expect to do some searching, maybe anything up to 0.25 miles?

Cheers, Kerry.

jlr · 05-26-2004, 07:02 AM

Thanks. It looks like I'll ditch the backup GPS for a Loran. Hate to add another antenna. Do all Lorans still need a whip antenna?

Sea_Dad · 05-26-2004, 07:10 AM

yes. The antenna has a pre-amplifier in it's base.

First Light · 05-26-2004, 08:47 AM

And the 8 ft whip, yes. There are shorter whips - I've seen um as short as 4 ft, but you stand the chance of degraded reception with the shorter version.

jlr · 05-26-2004, 08:51 AM

I have a charter captain coming aboard to fish with some clients. All of his "spots" are in TD's and I wonder whether the 1500 foot accuracy of the phantom loran on the 951 XD is too broad--hence I may need to buy a Loran as a backup. I am surprised that with 9' accuracy on DGPS, the Loran readings would be off by as much as 1500 feet.

Sea_Dad · 05-26-2004, 09:14 AM

The phantom is nothing more than funky math that is terribly inaccurate. Save yourself the embarrassment, and get an actual loran.

jlr · 05-26-2004, 09:39 AM

Will do. The last Loran I had I bought in 1991. Retro boating--as my kids would say.

amada8 · 05-26-2004, 02:53 PM

Quote:

jlr - 5/26/2004 8:51 AM

I am surprised that with 9' accuracy on DGPS, the Loran readings would be off by as much as 1500 feet.

Think about it. when you set up your unit to input TDs, the 941 will convert these into decimal numbers L/L and save to memory as a decimal. It has to convert because you have a DGPS unit, not a LORAN machine. Northstar calls this Phantom LORAN when you set up your display for LORAN. After input, you can output in several formats, including DGPSxx.xx.xxx or LORANxxxxx.x

If you have accuracy of 9' with DGPS, then you will also have the same accuracy with the LORAN inputted numbers when you set the display to xx.xx.xxx You will find that spot everytime! Problem is, you will be finding the 'converted' number everytime and the conversion performed by the 951XD is not accurate. It's good, but not excellent. You will still need to hunt for the LORAN spot that the captain gives you..... which could be as much as a quarter mile away.

Just one more thing. I reread your post and may have misinterpretted your statement. If you were implying that you expected Northstar algorithems to accurately convert your TDs, then you have jumped the gun on technology. There is not a perfect conversion tool as witnessed by all the threads titled "How do I convert..." Andren is good if you use the offsets correctly. But it is my understanding that the offsets cover a very small area and you will need to use several different offsets to cover your small fishing range. Not big differences in the offsets mind you, but enough to put you 100-300 feet away from 'the' converted spot.