Mark Naming Conventions

[MSchwiebert]

A little curious about this mark that I photographed earlier today,  yes it's near Delta Ohio - but South and not west, so this leads me to believe that it's name refers to its purpose more so than it's location.  If that is the case, what would it have been the base of?

[kayakbird]

Somewhere in that area there should be the other end of this 'Base Line'.  Does this mark have a PID?

 

For trigonometry to work in a multiple triangulation station array you must have one very accurately measured line to start reading angles from.  The longer the better and usually double measured with a steel tape under a weighted pull, with the ambient temperature noted and corrected for.  I believe that there was one north of Havre, Montana at about twenty miles.  Could only recover one end when I was there a few years back.

 

kayakbird

[Bill93]

In the national triangulation they used a carefully measured baseline about every so many tens? of miles to avoid a buildup of small errors in the triangulation. 

 

As mentioned above they were VERY careful in the measurement of the line.  It was laid out with a theodolite and marked with temporary monuments at intervals.  I think most baselines were on the order of 10 km in length, but haven't researched that. Besides all the other precautions, they did a level run so they could correct the surface length of each segment to a horizontal length. Temperature and tension corrected taping was only part of the care used.  Each tape length was probably scribed on a piece of metal on top of a stake or more permanent monument, working under magnification.

 

Here's a discussion of a base line in Nebraska.

https://rplstoday.com/community/surveying-geomatics/geodetic-base-line-sign-dedication/

and one in California

https://rplstoday.com/community/gnss-geodesy/yolo-base-line-1881/

There are some good links in those posts, as well.

Edited October 28, 2018 by Bill93

[Bill93]

Delta East Base

https://www.geocaching.com/mark/details.aspx?PID=MC1516

 https://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=mc1516

Delta West Base

https://www.geocaching.com/mark/details.aspx?PID=MC1521

https://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=mc1521

They are about 14.56 km (9.04 mi) apart.

Edited October 28, 2018 by Bill93

[MSchwiebert]

Thanks! I did see that there's a Delta East Base station after I posted this.  Makes more sense now.  Generally speaking, which direction would they work off the Baseline from? Also makes sense that its along a (now abandoned) railroad right of way, as the Oak Openings preserve is between them.

Edited October 28, 2018 by MSchwiebert
additional info

[Z15]

fyi........................................

[Z15]

Measuring Base Lines was a huge task of its own, special crews just to do that back in da days..

Base line measurement party. Triangulation party of Carl Aslakson

 

Graded road made to measure Epping Plains Base. Base Line party of Alexander Dallas Bache
 

Edited October 28, 2018 by Z15

[Z15]

https://www.photolib.noaa.gov/cgs/index.html

 

[kayakbird]

Please include some PID's - makes it a lot easier to provide information.  Be aware that secrecy is not a part of Bench Marking.  kayakbird

[MSchwiebert]

10 hours ago, kayakbird said:

Please include some PID's - makes it a lot easier to provide information.  Be aware that secrecy is not a part of Bench Marking.  kayakbird

Will do going forward,  no intent on being secretive - still learning what is expected information wise :-)  Thanks!

 

[Z15]

https://archive.bangordailynews.com/1991/11/22/epping-plains-site-of-ambitious-1850s-survey-base-line-in-columbia-one-of-6-used-to-map-eastern-u-s/