The Future of GPS

[CarinaPDX]

GPS modules used in phones are designed for low power first, and while very good do not compare to modules designed for navigation devices. So any comparison favors the nav modules.

The newer two band nav modules (specifically SirfStar 9) reduce what might be called jitter: the error curves are the same but with less noisiness (i.e. small, short deviations). This should improve any calculations based on comparing closely spaced positions (e.g. speed, heading) but not very much to absolute position. GPS accuracy is spec'ed for 95% of the time; that other 5% can, and often is, ten or more meters off. So while most of the time our GPS systems can show us in our slips, or the next one over, that last 5% of the time it can be off by a lot. AFAIK this is not something that the new GPS modules can fix - it is a limitation of propagation. Some survey level systems work by comparing the module position with a nearby receiver at a known position, often at a survey mark. The future for accurate GPS-based instrument piloting is for marinas to operate that second receiver and transmitting the results. (Being close together both modules experience the same propagation errors so the relative position is very accurate.)

Greg

[Djarraluda]

Originally Posted by Jim Cate

While this is a neat techo feat, it seems more exciting to surveyors than to sailors. The current accuracy for GPS location seems adequate for our sort of navigation.

But then I started out doin' celestial and a small cocked hat was exciting then!

Jim

I am with you Jim, always taught that any navigator who points to a single point and stated that was their position was lying!
Roger

[Captain Anthony]

Following with interest

[SoonerSailor]

Using the newer L5 signal with the L2 signal allows, since they are different frequencies, better compensation for ionospheric perturbations of the gps signals. This is an incremental improvement but not really a dramatic one. The real impetus for L5 comes from the need for a protected radio band with a better guarantee of signal integrity, which the aeronautical community needs. L2 signals are not in a band that can be so reliably protected from interference.

[MicHughV]

the old salts used to take their thumb, give it a lick (to add drama) and inscribe a 4" circle on a chart and tell whomever was interested "we're sumwhare's in this area"

[CyKlop]

Originally Posted by CarinaPDX

So while most of the time our GPS systems can show us in our slips, or the next one over, that last 5% of the time it can be off by a lot

A fun experiment to do is, while tied up in a slip, start your chartplotter and run a track for 12 or 24 hours. You'll get a good idea of how much your chartplotter might be off. After all, you know that your boat (and receiver) isn't moving (very much), so the track gives you an idea of the errors possible.

That's not a ding against chartplotters or GPS receivers. It is simply a pointer to be aware of some of the inherent limitations of the technology.

[Elleroo]

My son works in radar, and was on board a naval ship doing daq. Said he was in the ops room, and was wondering what the box in the corner, turned off, was. Loran was the answer that came back, and apparently they test it monthly....


GPS is there for military use, and can be turned off in a blink.


I'll stay with my sextant and Walker log, and hand bearing compass and old B&G rdf on aero beacons.

[svfinlandia]

Originally Posted by Captain Anthony

Following with interest

I also.

Al, S/V Finlandia

[Pat_D]

Originally Posted by Elleroo

My son works in radar, and was on board a naval ship doing daq. Said he was in the ops room, and was wondering what the box in the corner, turned off, was. Loran was the answer that came back, and apparently they test it monthly....


GPS is there for military use, and can be turned off in a blink.


I'll stay with my sextant and Walker log, and hand bearing compass and old B&G rdf on aero beacons.

Are the loran antennas even still in place? They certainly are not continuously broadcasting...

[StuM]

Originally Posted by Pat_D

Are the loran antennas even still in place? They certainly are not continuously broadcasting...

". The Coast Guard terminated the transmission of all U.S. Loran-C signals in February 2010 and began dismantling stations."

However, their is an alternative coming:
https://www.gpsworld.com/innovation-enhanced-loran/


https://www.xyht.com/gnsslocation-te...turn-of-loran/

[Jim Cate]

GPS is there for military use, and can be turned off in a blink.


I'll stay with my sextant and Walker log, and hand bearing compass and old B&G rdf on aero beacons.

GPS is so embedded into our everyday life that the thought that the "military" could shut it down is pretty far fetched. In its early days, yep, just remember selective availability, but not now IMO.

And as one who started making his offshore passages with celestial, it's great to have the skills, but to eschew GPS nowadays is foolish, again IMO. We were in Fiji a few years back when a British yottie with similar ideals lost his boat in the Lau group due to nav errors. I view that as a self inflicted loss...

Jim

[donradcliffe]

I delivered a boat with a SkyHook dynamic positioning system. The concept is you maneuver within a foot of the dock, set the SkyHook, and then put your fenders out and step across with your docklines. I can see that a more accurate GPS would help.

[Norsailor]

Originally Posted by goboatingnow

The big advantage, will be low cost RTK gps will be heading info , the data of the flux gate compass are numbered

Heading is where your bow i s pointing. Where the boat is going is, as we all know, a different matter, mostly named TMG or Track Made Good. What the plotter software does, is making a history of your recent positions, which
equals the TMG.
There is probably a few things I don't know about GPS technology, but pls explain how you can determine the compass heading from a GPS signal. Especially when the boat is not moving.

[LakeSuperior]

As pointed out in a couple other threads, GPS speed is determined using the Doppler effect and not distance divided by time.

Additionally, the GPS satellite clocks are periodically corrected because they run faster than land based clocks as explained by the general theory of relativity. The gravitational field is weaker as the range from the center of the planet increases.

[double u]

Originally Posted by Jim Cate

...But then I started out doin' celestial and a small cocked hat was exciting then!

Jim

I am tempted to say "...the good old days...", but maybe I only remember the excitement of "having it gotten right" & have forgotten the soul-searching, triple checking & standing on the foredeck & listening (just in case)