Hi David ,
I am assuming , that you are looking for software,( on a computer ) since you did not show any.
Take a look at this, the programmer is Barry Graham. Barry gave this to LSU members,so give him a thanks. He has two versions ,one with Azimuth and one with Bearings. the one with bearings is North America or American version. I do not no what you mean, with 2 unknowns.( Does this mean Open) There is also some Spreadsheet programs there must be one on traverse. There is a lot of calculator programs even for emulators. SGS has a very good Cogo for the HP 50 G free the emulator and the program. Barry's programs and the spreadsheets are maybe the easiest,although The calculator SGS programs work very good. There are Hp 35s programs which you have to key in and there are Casio survey programs that some you have to key in. So take a gander and see if any of this is what you are looking for, spreadsheets are right in front you. I am sure there are some I did not mention.
I think the poster means missing bearing or distance on one leg and missing bearing or distance on another.
Hi Barry, first how have you been doing,I hope well.
I do not know what he meant, But he has been surveying a long time,but your cogo program works as good or better as any I have use. And I have several including Cogeo and it is not free. So I do not know what David is looking for but I like yours a lot ,and thank you for sharing it with us.
I got to thinking about , " allowing Two Unknowns" , the only reasoning I could come up with is are you asking about two Missing distances. A program that would calculate this. A example may be, once all the known sides have been entered (order does not matter), the resultant vector of the traverse is known. This forms one side of a triangle, with the two unknown lines forming the other two sides. We know the length of the resultant vector, and the azimuths of all three sides. So we can deduce all three angles.The triangle is solved using the Sine Rule. The ratio of the sine of the angle opposite the resultant vector and the resultant vector’s length are stored and used with the sines of the other two angles to compute the lengths of the two missing sides. This is all I can think of.
After , Thinking about what I said about the Two missing Distances, and what Barry said, I also considered the algorithms of a missing Bearing and distance. For missing bearing and distance, the missing line must be the last line in the closure.And for double missing distance, the missing distances must be on the last two lines of the closure. I think I could write a small program In RPN or RPL to do this no problem . Equations in RPN or Algebraic expressions or notation in both would also work, but as there is no redundant data to allow computation of a misclosure. That said this still could be useful if required.
B 1n - B ⁿ n-1 = ± (180 - y )
B1 ⁿ-1 - B 1n = ± ( 180 - a )
SIN (180 - y) = SIN ( y )
SIN (180 - a ) = SIN ( a )
± a = c* SIN ( a ) ÷ SIN ( y )