MSchwiebert Posted October 28, 2018 Share Posted October 28, 2018 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? Quote Link to comment
kayakbird Posted October 28, 2018 Share Posted October 28, 2018 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 Quote Link to comment
Bill93 Posted October 28, 2018 Share Posted October 28, 2018 (edited) 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 Quote Link to comment
Bill93 Posted October 28, 2018 Share Posted October 28, 2018 (edited) 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 Quote Link to comment
MSchwiebert Posted October 28, 2018 Author Share Posted October 28, 2018 (edited) 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 Quote Link to comment
Z15 Posted October 28, 2018 Share Posted October 28, 2018 fyi........................................ Quote Link to comment
Z15 Posted October 28, 2018 Share Posted October 28, 2018 (edited) 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 Quote Link to comment
Z15 Posted October 28, 2018 Share Posted October 28, 2018 https://www.photolib.noaa.gov/cgs/index.html Quote Link to comment
kayakbird Posted October 29, 2018 Share Posted October 29, 2018 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 Quote Link to comment
MSchwiebert Posted October 29, 2018 Author Share Posted October 29, 2018 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! Quote Link to comment
Z15 Posted April 6, 2019 Share Posted April 6, 2019 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/ Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.