I am trying to calculate the chord bearings on a radial lot.
I will be stating bearings for both sides of the lot heading towards the radial point. I have "built" the lot and know what the correct chord bearing should be using my surveying calculator. What I am trying to find out is what is the math formula to determine this chord bearing.
the left side has a bearing of S 46 46 36 W with a lot dimension of 125
the right side has a bearing of S 73 20 05 W with a lot dimension of 125
the delta or central angle is 26.3329
the radius in the front is 151.144.
the radius in the rear is 276.144.
the arc in the front is 70.059
the arc in the rear is 128.00.
Thanks for your help
the chord bearing determined by the calculator for the front is S 29 56 39 E or N 29 56 39 W depending which direction you are going.
I am currently using a Carlson Mini 2, (using SurvCE, ver 4.00.17) and it does not have the capability like my old HP48GX, or TDS to create a tangent curve in the manual travers mode. I think I have figured out a way to build it if I can mathematically calculate how to determine the chord bearing. If anyone else has any experience with the Mini 2 and knows a better way to do it I would like to know that as well, Carlson Tech Support has simply stated that they have that on their desk version. When I explained to them the surveyors in the field need this they could not understand why.
If I understand your description, you should be able to find the information in any relevant textbook or reference, or derive it from basic trig.
If you draw a perpendicular to the chord through the radius point, you will have formed two right triangles, and split the delta in half. The angle between the radius and chord is then 90 - delta/2
I would note that your delta seems to be in packed format and should be read as 26d 33' 29". I was confused, as to why its format didn't match that of the bearings.
I use packed format on my old HP calculator, and can see that it was once useful with the restrictions of the equipment, but most gear should be able to afford spaces or other punctuation nowadays to reduce confusion with decimal degrees.
No formula necessary. It is only a matter of adding and subtracting angles to obtain the chord bearing since both lines are radial. The difference in the side line bearings will be the Delta of both curves. 90° from either one of the side lines will be the Tangent bearing. ½ Delta either added or subtracted from the Tangent bearing, whichever case applies, will be the chord bearing.
:good:
Bruce, I don't know what program you were using but you ripped through that pretty quick. I got the same answer you got, but ws looking for a formula which although I already knew about creating the angles for the lot by taking 1/2 of the delta and adding or subtracting from 90 degrees, I never thought about trying that method.
Bill, thanks for the wake up call , I do remember the formula for the 9- - delta/2, and will try to use it in the future on my new Carlson mini.
Thanks again
Charles , thanks like I mentioned to Bill, I will try that ethod, and all of you thanks for the quick response.
Hopefully I can get this new Carlson working better.
The formula to figure the chord length is: 2Rsin½D (2 x Radius x Sin ½ Delta) in case you need it.
