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Plat Calcs
Posted by fielddog on March 10, 2024 at 2:32 pmHow would you calc the following?
(1) Look at the small curve (R = 255.32′, L = 44.07′) to the west of lot 222. Would you assume the line from the P.C. to the radius point is radial (N 40°55’11” E), or would you turn 90°00’00” left from the P.T. using a B.S. bearing (forward tangent of the curve) of S 58°58’20” E?
(2) Look at large curve (R = 679.25′, L = 485.88′) to the west of lots 224 – 232. Does the tangent bearing of N 40°59’06” E indicate a nonradial curve? Would I simply use that bearing as a B.S. bearing and turn 90°00’00” left from the P.C. to set the radius point?
I haven’t been able to close the legal description, and I think these two items are the reason.
Please see the attached files.
MightyMoe replied 6 months, 1 week ago 6 Members · 22 Replies 
22 Replies

Here’s the plat. I couldn’t figure out how to attach it to my post.
MH 
Hmmm. I think that description is wrong, that’s the central angle (delta) and not the tangent. Try that.
🤷🏼♂️

I ran the bearings and distances just like they show on your map and everything closes using 90 degrees for setting the 30′ radius point. The map is good so check your work.

1.) Seems clear to me the curve is tangent to the south line of lot 222.
2.) Yeah, appears to be a nontangent curve, so 90 from the tangent bearing etc.

@ Landbutcher464MHz
What 30′ radius point? Thanks for your help.
MH 
@ BStrand
What would be the purpose of using a nontangent curve? Aren’t curves designed to fit tangents? Thanks for your help.
MH 
What would be the purpose of using a nontangent curve? Aren’t curves designed to fit tangents? Thanks for your help.
No no, nontangent as in not tangent to the lines in and out of the curve. Different thing than the tangents to the PI.

I don’t have time to do any calcs, but the curve appears to be tangent to the south line of the lot, the west lot line is not radial to the curve. The bearing to the radius should be N310140E (off the top of my head) and the distance to the radius is shown for both sides of the street.
That is a really nice plat, hand lettering is classier than Autocat drawn plats.
From 1960 I wouldn’t expect super accurate findings, it’s all about monumentation 60+ years later.

This 30′ radius curve is perfectly tangent to both lines. See attached. The data calcs out tight just like Gary G. said.
 This reply was modified 6 months, 1 week ago by Landbutcher464MHz.

@ MightyMoe
That is a really nice plat, hand lettering is classier than Autocat drawn plats.
I agree. I’m keeping this plat as an example on how a plat should be drawn. The two calc problems I pointed out were a challenge for me. It was a good learning experience.
MH 
@ GaryG
Thanks, Gary. You are too kind. So, it appears that line 312 – 311 is radial.
MH 
@ BStrand
No no, nontangent as in not tangent to the lines in and out of the curve. Different thing than the tangents to the PI.
Looking at GaryG’s drawing, I’m a correct in saying that the tangent bearing of N 40°59’06” E is for the piece of 18.7′ arc of lot 224?
MH 
Correct, they give that bearing to set up the overall curve for the plat boundary.
I do see I have a fat finger bust in defining the radius of the next lot north. The intersection is correct, just messed up the radius when I built the figure.
NOTE: Replaced plat with corrected radius.
 This reply was modified 6 months, 1 week ago by GaryG.

Looking at GaryG’s drawing, I’m a correct in saying that the tangent
bearing of N 40°59’06” E is for the piece of 18.7′ arc of lot 224?Yeah, and every other lot until the pin around the middle of lot 232.

@ BStrand
I’ve never seen anything like that before. Is there something special about the curve that dictates that?
MH 
I’ve never seen anything like that before. Is there something special about the curve that dictates that?
The 679.25 radius and 485.88 length dimension by lot 227. Though when I add up the lot lengths between the pins I get a number that’s about 5 feet different, so maybe I’m misreading a number somewhere.

That’s typical, my guess since it’s along the property boundary is that it ties into a monumented line that didn’t quite match up with the math. So to “fit” found evidence the curve was adjusted to match monuments or an established line. That’s my speculation. The plat is giving a tangent slightly off the lot line to facilitate the location of the curve.
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