Last month we were cleaning out the supply room, and I found a brand new Philly rod target still in the box. The new rodman asked "What's that?". I told him I used such a target years ago to do mortgage surveys, so I could read the rod from long distances without actually reading the rod. The rodman would set the target to my crosshair and tell me what the reading was. The boss wanted it done that way to save time. Anyway, a bit of nostalgia.
I am among the group that approved of their use.
They solved the splitting of hairs decision.
I remember using something like that years and years and years ago.
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To really blow his mind, explain how the vernier scale works.
Looks to me like it's out of calibration. Shouldn't the zero mark match a straightedge across the painted lines?
Bill93, post: 401194, member: 87 wrote: To really blow his mind, explain how the vernier scale works.
Looks to me like it's out of calibration. Shouldn't the zero mark match a straightedge across the painted lines?
Bill, if I remember correctly the scale on the target was used by the rodman as a vernier. The instrument man would instruct the rodman to "tune" the target with up or down motion with the black knob until centered with the observing instrument's cross-hairs. At that time the vernier could be read by either the rodman, or most generally the PC with the field book that was standing close. The vernier, which i believe graduated 0.09' into ten equal hashes, allowed a rod graduated to the hundredth to be read to the thousandth.
And that's probably why it has stayed in such pristine condition in a box all these years.
Paden, that's pretty much my understanding of it. I've used verniers (I'm probably a bit older than you), although never on a level rod. I figured the new rodman was probably too young to ever have seen a vernier anywhere.
My observation about the zero calibration may be wrong because of parallax in the photo.
Bill93, post: 401234, member: 87 wrote: Paden, that's pretty much my understanding of it. I've used verniers (I'm probably a bit older than you), although never on a level rod. I figured the new rodman was probably too young to ever have seen a vernier anywhere.
My observation about the zero calibration may be wrong because of parallax in the photo.
The new rodman, in his late twenties, has only been surveying for six months. I'm happy to say he's taking an interest in surveying!
If it was smaller it would make a nice bottle opener