Original Surveys / Telegraphic Time Signals

> Celestial Observations in connection with telegraphic time signals to establish location...Think about it! Are we more technically advanced today then the US Field Surveyors of the 1800s? Are we intellectually and physically as capable?

Well, had beerleg.com existed at the time, surveyors would still be arguing about the proper way to do the time transfer via telegraph and the best way to make longitude observations.

Hello Kent...Hm hm hm Thats for sure.They had a lot more to contend with and lesser means. The difference I believe was made up with their skills and abilities.

> Hello Kent...Hm hm hm Thats for sure.They had a lot more to contend with and lesser means. The difference I believe was made up with their skills and abilities.

Well, consider just the difficulty of doing an accurate time transfer of timings via telegraphic signal. First, you need to figure out how to estimate the delay in the signal. Presumably you do that by rigging a relay at the remote station so that when a time signal is sent from the station with the time standard, the time signal is echoed back to the sending station so that the lag time between sent and echo received can be measured.

To do that impersonally, you can use a clock-driven drum or something similar that winds a piece of paper at a regular rate and rig an apparatus to make a mark on the paper when a time signal is received. If you want to get scientific, at the station of observation, the observer marks time by keying the same apparatus to mark the paper time record at the instant of some astro observation.

If you assume that the delay in the relays will be the same each way when the time signal is echoed back to the sending station, then the delay in the signal between the station with the time standard and the remote station where time is to be transferred to is just half the time difference of the sent and return parts of the echo.

There are a number of survey archives which describe actual activities in regard to telegrachic transfer.

Here is one of the later ones I am aware of:

http://www.google.com/url?sa=t&rct=j&q=arthur%20d.%20kidder&source=web&cd=8&cad=rja&ved=0CE0QFjAH&url=http%3A%2F%2Fbooks.google.com%2Fbooks%2Fabout%2FObservations_and_calculations_and_field.html%3Fid%3DktoMAAAAYAAJ&ei=BB9xUJ3fOeyP0QGS2YCgCA&usg=AFQjCNF9D8ms-5HFG8gBVjTAPJZbBhyU2A

That should be a report authored by Arthur D. Kidder on one such determination. The telegraph set that was used is actually in the possession of the office which I retired from. It has OK-TX significance.

One question remains that I have not analyzed, is that in spite of the care taken the results did not seem to be that well respected and may even contain some systematic errors.

- jlw

That's a great link, Jerry.

Here's one to an illustration of the Saegmuller Chronograph that was used in the timings. The paper sheet was mounted on a clockdriven drum, just as recording thermometers were at one time, the record being a trace by a pen on the paper sheet as the drum turned.

Saegmuller Chronograph

At the Mouth of the Mississippi River, the river breaks up into several passes called the "Birdsfoot Delta." Just above that is "Head of Passes," and was the southernmost terminal of the telegraph lines to Venice, Louisiana. The shift in geodetic longitudes of USC&GS Triangulation Stations is stark because south of there the astronomical longitudes were determined by chronometers.

My analysis of that was published in "Surveying and Mapping" back in 1979: Datums of the Lower Mississippi Valley.

Interesting how those in history used existing technology to solve measurement problems. One I was impressed with in the days of chronometers and black powder was how they were used the two to determine the length of a baseline over water so shorelines could be charted. Two vessels anchored, one firing a small cannon, other vessel measuring time from the visual smoke of firing and the time lag when the report was heard, provided the means to compute distance. Sextants then measuring angles to common points on shore from each vessel to a point that could be charted, by leapfrogging around an island or along a coastline a lot of data could be gathered. Some of those charts were surprising accurate and used up until WW2 in the Pacific.
jud

hey jud,
what amazes me is how they did what they did without the technology we have today and came up with similar results. I believe they made up for the difference through skills and abilities...think about this...in the 1700s some science academy puts together a plan to observe the transit of venus, mulitiple observations from around the world, without real time communication everything is done through horse delivered message which coordinates a team of astronmers to be taken two oceans halfway around the known world to make it to the south pacific by a certain deadline by wind power and celestial navigation, meanwhile gathering, hunting, foraging, and provisioning as you go amongst natives wanting to sacrifice you....make it the observation location, set up an astronomical observatory, observe the transit of venus on the coordinated specific time that every other team is doing around the world, document your results, pack up and sail back against sea and weather and not to mention making some maps of shoreline with depth soundings whose accuracy is respected today...come on...these guys were beyond any sense of courage and resourcefulness that I believe I may have....despite all the conjecture you have to respect what they did....hey check this book out, its an interesting read

http://doylemarine.com/?action=product&id_product=70399

rlshound

Hello Cliff,

Thank you for your input. I'll look into your publication.

Thanks,

rlshound

Hello jlwahl,

Thanks for your input. It amazes me how they accomplished what they did.
I'll look into the book you mentioned.

Thanks,
rlshound