Multilateration and Local GPS in Aviation

Only by standing still, and then falling out of the sky. Just think about it. ...Oh, never mind.

Possible applications occur to me by the dozen - well, half-dozen given that I have more immediate things to do. Use some imagination. And don't forget drones.

Quiddich (ok, other athletics / extreme sports), surveillance/exploration, aerobatics, surveying (h/t to the poster who mentioned it already) & measuring, remote sensing, precision-guided munitions, higher-resolution route finding.

Could not imagine why such precision is required in aviation. Even Cat III precision approach doesn't need anything that precise.

Most airports use LAAS (GBAS), which is a local area augmentation service that takes over for GPS to provide precision approach guidance for aircraft. GBAS precision is sub-1 meter.

I know that Wide Area Multilateration (WAM) is now filtering its way into various airports, but I don't know that much about it. I have been out of the aviation GPS systems for almost 6 years now. I though that WAM was more of a mechanism to get better or more efficient traffic patterns to and from the airport.

For your search you might want to start contacting some universities and see if you can track down some professor or PhD doing research on the subject.

The tech to actually achieve this particular level of GPS accuracy (if it is even possible using the mentioned technique) is outside my expertise, but from my experience I cannot think of any applications - aviation, military, exploration, tracking, etc where this increased accuracy would be of benefit over existing GPS accuracy.

Even with precision guided munitions (or directed energy) the devation, tolerance, uncertantity levels inherent in the guidance systems, construction and plain natural environment and physics involved are going to be larger to much larger than the potential 1mm tolerance offered by the GPS for targeting purposes.

What possible market and use do you think there is, and bare in mind that non-military uncontrolled consumer GPS is still limited in accuracy by governments, and the new technology is bound to be more expensive?

For precision surveying and construction nothing really beats good old ground optics and lasers for cheap and repeatable accuracy.

I am not sure the industry would take to relying on GPS over local optics, but if affordable precision and repeatable GPS is possible then there could potentially be a market here. Industry standards would have to be changed however and like the automotive industry this could kill any new GPS use in the industry.

All of the earthwork for the fifth runway at Hartsfield-Jackson International Airport in Atlanta was staked using centimeter-level accurate differential GPS. One company had the contract to do all of the fill work and another company to do all of the cut work. Centimeter accuracy is .03 feet, which is more than accurate enough for earth work. If millimeter level accuracy could be obtained with GPS that would be less than 1/16" which is less than the 1/8" accepted accuracy for building layouts. There are many applications where that level of accuracy in the construction industry would be more than adequate.

As for the industry accepting GPS, take a look around and see how many surveying and construction companies are relying on centimeter level accurate differential GPS at the current time. If it can be shown that repeatable measurements in the millimeter range were obtainable then those same companies would put their optics and lasers in the same closet as there chains and tape measures that they used to use.

As a side note, when they were doing the planing for that runway, a portion of I-285 around Atlanta had to be surveyed because the runway actually goes over the interstate. The company that had the contract to do the location of I-285 was facing astronomical fines if they were going to shut down the highway to survey it. They bought what is called a reflectorless total station to do the job. When you see someone surveying they usually have a reflector on a pole that is used to reflect a laser (like "jack of all trades" was referring to) back to the total station to get a distance measurement by using modulated wavelengths and interference patterns, not with time delay as most people, even within the industry, think. (See https://en.wikipedia.org/wiki/Total_station#Distance_measurement) A reflectorless total station can measure distances to any object that is relatively light in color without the use of a reflector. The cost of the instrument was less than the cost of the fine and the job took less time to complete than it would have with a reflector so they basically got a reflectorless total station for free. Not long after that they came to realize that a differential GPS would be acceptably accurate for their earth work on the fill side of the project.

Basically what I am saying is that the industry will adapt to new technology if it is proven to them that they can get acceptable accuracy at a reasonable return on their investment.

It can't.

Which autonomous airborne vertical delivery systems are used for building? Could you drop a link, because I could only find is autonomous airborne for military which uses parachute..

Sorry if my note implied such systems are being currently used for autonomous building. There may be, but I'm not aware of any.

There is a lot of development going on, though, such as with control programs displayed in this LINK. See the videos down the page.

To me, it's just a matter of time. I was involved in a project that demonstrated autonomous take-off, flight and landing of a CH-47 Chinook helicopter. This was pre-GPS and involved ground based laser tracking of the aircraft returning to within a meter of its takeoff point.

And here's an ARTICLE about a Marine project for drone delivery. It doesn't say if it's autonomous yet but I'm sure that's only a matter of time.

And any of these delivery systems could be pilot programs for assembly systems, IMO.

Hooker

As multilateration uses Time Difference of Arrival (TDOA) method, i was thinking that using very precise timing device could give such accuracy. Similar technique is used in Satellite Laser Ranging. But ok, it really does seem that extreme precision is not necessary in aviation.

Thanks for sharing your opinion!