Oddity: Where did "I" go, and how'd "M" show up?

[foxtrot_xray]

This is another, which I was always amused at.

In Marion, IN, on the courthouse, there are three reported stations. One is an intersection station, the courthouse dome. This one can be ignored.

 

That leaves these two:

LA1607 DESIGNATION - I5
LA1608 DESIGNATION - I 5 RESET

Okay, this is fine, nothing unusual yet.

Until you get to the courthouse. Let's go look at "I5" (which is oddly missing that space, but..). It says it's "AT" the west entrance. And then gives info on how the stone is loose and it should not be used. I don't care how much you look - you won't see anything even close to resembling a disk. Or even an old drill-hole used to mount the disk. There ain't any indication that anything was there at the entrance.

Now let's go look for "I 5 RESET". Apparently, it's 16 feet south of the west entrance. Well, hey, guess what - there's a disk there! .. But wait.

It says "M 371". Dated 1992. Okay, so.. it's recent, NOT from 1962. And it is NOT "I 5", even if it somewhat fits the description of I 5 RESET. So, let's go to the NGS website, and see if we can find "M 371". Doing a search by Station Name, in Indiana - Not only is there no 'M 371' in Indiana, there isn't ANY station with "371" in it in the state. (No P 371, N 371, J 371, etc.) In fact, there are no "371" runs in Ohio or Illinois, either!

 

Edited August 10, 2020 by foxtrot_xray
Fixed locations

[Bill93]

The original disk in the wall must have gotten removed and somebody decided to replace it in 1992.  Since then it was not based off of the original I5, it couldn't be a reset, but would have to be measured from other bench marks.  Indiana does have a 370 line, so although that did not fill out the alphabet I can see why they went to 371.

 

I'll bet more 371 disks could be stumbled across in that vicinity.   But the 371 series measurements seems to have not been completed or the measurements rejected for procedures and quality so no data sheets.

[DaveD]

While I can't speak directly to a line "371" in Indiana, it's highly likely there are more as Bill93 noted.  It certainly wasn't normal but there were several instances during my tenure at NGS (72-13) where one or more level lines were set and for a variety of reasons never leveled to.