Wednesday, January 22, 2014

Surveying the first transcontinental railroad

From: "Erica Brandt"

I was researching the Transcontinental railway to use as an illustration. Basically how the two sides needed to come together, and if they were one degree off over time, would not have met in the middle.

But I can't find any details on line detailing the actually engineering/mapping of how the two sides were able to meet at the same place on May 10.

I have read that they were only working miles apart as they got closer, but could you point me to anything detailing how they actually mapped it to come together? ...

—Erica Brandt


Blogger CPRR Discussion Group said...

From: "Larry Mullaly"

... Aligning the tracks of the two system was much more of a political than an engineering challenge. Both companies wanted to claim as much mileage as possible because of the bond support this provided from the federal government. The Central Pacific, for example, aspired to build to a point many miles east of Ogden but never laid track that far.

At the time the agreement to meet at Promontory was reached, the Union Pacific and Central Pacific already had surveyed and staked out individual parallel lines for many miles beyond the point of junction. They had also done a considerable amount of grading (earth preparation for the tracks). However, grading was relatively cheap – it was trackage, bridges, culverts, and heavy cuts and fills that cost.

Once the point of encounter was established by the separate managements, survey teams from both roads would have worked together to obtain as much "tangent" or straight track in both directions as possible. Curves were avoided wherever possible and both sides would have wanted to reach a compromise.

A meet would have required a realignment of both railroads to some degree. But realigning the projected line of the road on level ground such as Promontory should not have posed much of a technical problem. ...

—Larry Mullaly

1/23/2014 2:40 PM  
Blogger CPRR Discussion Group said...

From: "Kyle Wyatt"

I will add to Larry's discussion a couple of specific at Promontory. By the May 8, 1869, intended ceremony date, both companies had already built parallel grades through the Promontory Summit area. The Central Pacific delegation arrived in time for the planned May 8, 1869, ceremony, but the Union Pacific delegation was delayed, so the ceremony was rescheduled for May 10, 1869. At the time the Central Pacific delegation arrived, no connection had been graded between the grades of the two railroads. Central Pacific intended to grade a connection on the morning of May 9 (I believe that is the correct date – this from memory) to the Union Pacific depot site. But the night before the Union Pacific stole a march on the Central Pacific and graded their own connection just West of the depot site. And so the Golden Spike ceremony took place on the Central Pacific alignment, at the end of the connecting track that the Union Pacific had just completed.

As noted by Larry, grading and track construction on the relatively level plateau of Promontory Summit was pretty easy, and did not require a lot of advance engineering work. My impression is that the Union Pacific connection track was built quickly and easily, with little advance work needed.

—Kyle Wyatt

1/23/2014 2:45 PM  
Blogger CPRR Discussion Group said...

See, Finding the Way and Fixing the Boundary: The Science and Art of Western Map Making, As Exemplified by William H. Emory and his Colleagues of the U.S. Corps of Topographical Engineers, by Rollie Schafer.

1/23/2014 3:03 PM  
Blogger CPRR Discussion Group said...



Reports of Explorations and Surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean, made under the direction of the Secretary of War, in 1853-4, Volumes I-XII.
Washington, Government Printing Office, 1855-61

1/23/2014 3:09 PM  
Blogger CPRR Discussion Group said...

The exact final location of the Central Pacific Railroad's route was established over the Sierra Nevada mountains and in Utah by Lewis Metzler Clement, as locating engineer. The first exhibit that visitors see when entering the California State Railroad Museum in Sacramento is of Clement surveying with his equipment. Skilled use of that equipment measures angles accurately so that the location can be determined using trigonometry.

1/23/2014 3:18 PM  

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