The texts get into some imaginative concepts but in actuality, how long a longest line was regularly observed?
Given those observations what calculations are appropriate.
In the same light what are the longest observed EDM distances near the surface of the earth?
Paul in PA
Triangulation: Mt Shasta to Mt Helena: 192 miles, 309 km is the longest I have ever read about.
EDM: I don't remember how far, but I think it was in Texas, much shorter than the above line.
GPS: ????. I have had to process lines 1000's of km long in Egypt and India when establishing control there, because there were no CORS any closer. Nowadays, there are way more CORS, so the lines don't need to be quite as long.
The longest EDMI observation that I ever did was ~206,000 feet (Electro-Tape). I'm sure that isn't even close to the "record."
Loyal
In the 1950s, Army Map Service did a number of SHORAN and Flare Triangulation observations between islands and continents, but I do not know the specific lengths.
I received an emailed requesting clarfications on my questions. My reply:
Longest direct line observed with a theodilite, etc from one point on earth to another point on earth?
How to handle that observation in reducing same to values that could be included in Least Squares or other adjustment?
Is it necccessary to use the full Direct/Inverse method, for lines that are geodetically short?
We pretty much no longer make such observations now with GPS available to make indirect but rather precise observations.
One cannot observe satellites or stars with observations that remain close to the surface of earth, so they are excluded.
Paul in PA
What about a flare dropped by an airplane inbetween two theodolites? That's what Flare Triangulation was all about. Radio time signals syncronized the observations.
Must Be Ground To Ground
Flare triangulation does not give the precision to justify using the Direct/Inverse equations.
Flare triangulation is a mapping and not a surveying tool.
Paul in PA
Maybe after everyone makes their best guess, we can email TDD and ask him what his longest observation was, and we can see how close the longest guess was to the truth...;-)