INS is not precise enough for the final approach segment
Maybe not in terms of aviation certification, but in the 1950s INS was good enough for a submarine to go under the polar ice cap and surface through the ice within maybe 10m of there they wanted to be.
The €20k fibre optic gyro boxes around today are accurate enough to place the nose wheel in the middle of the runway centreline, if you lose GPS at an IAF. But, as I said, it will never happen for GA because nobody will want to pay the price of the noncertified box, never mind the certified box. The instant GPS arrived, the bottom fell out of the Loran market. We may have out views on the wisdom of that but the practical situation is that if The Owner of the Universe (Garmin) don’t make it, it isn’t going to happen. And they (or anybody else) aren’t going to make it because virtually nobody would buy it.
… the bottom fell out of the Loran market. We may have out views on the wisdom of that but the practical situation is that if The Owner of the Universe (Garmin) don’t make it, it isn’t going to happen. …
I don’t know… LORAN needs flat, unobstructed terrain to work well (i.e. coastal regions) and we don’t have that everywhere. In my part of the world, we therefore never had LORAN. And even our coastal regions were served by the European product DECCA, not the foreign LORAN… Many years ago I used to fly on a C172 that had a DECCA navigation unit installed, the one and only I ever saw. Of course, it displayed nothing but zeros.
…but in the 1950s INS was good enough for a submarine to go under the polar ice cap and surface through the ice within maybe 10m of there they wanted to be.
10m? No way. A few hundred metres maybe, with constant position updates. Apollo 8 navigated to the moon and back with on-board navigation alone (INS based), but they needed to take around 150 star fixes to update their INS position during their voyage.
This is from the Aera 660 on a recent flight. Is Glonass operating at all?
Apologies for the Glonass pic being out of focus 
I did once get 1 satellite showing up – some months ago.
Plenty of Glonass here.
Simon
What app is that ?
Jan Olieslagers wrote:
But is there a real advantage to receiving Glonass on top of GPS? THAT was my question!
Yes, at high latitudes. This is primarily due to Glonass’ higher orbital inclination compared to NAVSTAR.
Other advantages are higher repeatability of DOP values on a daily cycle and, theoretically, a slightly higher resistance to narrow-band interference.
There is also their contribution to the Cospas-Sarsat space segment as a secondary mission, along with NAVSTAR and Galileo.
A disadvantage (as of ten years ago, things may have changed since) is a lower density of ground stations so anomalies in individual satellites may go undetected for longer than with other constellations. This is a political, not a technical drawback.
Finally, in terms of having GLONASS on top of GPS (i.e., alongside, which I believe was your question) there is the redundancy offered by two independently developed and operated technologies. Same applies for Galileo and Beidou.
AndroiTS
Not sure if it is still available.
Simon
The news from Russia is that Glonass is soon going to come to a sticky end.
Peter wrote:
Speaking from experience, there is a significant risk that within 5 years the Russian GLONASS constellation will simply cease to exist.
I don’t see any risk there I believe it’s guaranteed. Like in probability theory, that’s sure event.
Looking on the bright side, it means it’s unlikely the Russians will shoot down the GPS constellation, since they’re just as dependent on it as everyone else. Presumably using smuggled Garmin devices.
