HP Prime and Casio Prizm: Computation of “As-Built” Circular Alignments
Special thanks
to Jason Foose for bringing the topic to my attention.
The program
ASBUILT determines radius and center point of an approximate circular
curve. The program uses the least
squares method using the following matrices:
A = [ [ 2*x1,
2*y1, -1] [ 2*x2, 2*y2, -1 ] [ 2*x3, 2*y3, - 1] [ 2*x4, 2*y4, -1 ] ]
X = [ [ x0 ] [
y0 ] [ f ] ]
L = [ [ x1^2 +
y1^2 ] [ x2^2 + y2^2 ] [ x3^2 + y3^2 ] [ x4^2 + y4^2 ] ]
The matrix X is
solved by: X = ( det(A) * A)¯¹ * det(A) * L
The input for
ASBUILT is a 4 x 2 matrix, consisting of each of the four points.
The example:
(x1, y1) =
(6975.82, 6947.93)
(x2, y2) =
(7577.11, 6572.6)
(x3, y3) =
(8084.03, 6071.29)
(x4, y4) =
(8431.38, 5542)
The input
matrix is:
[ [ 6975.82,
6947.93 ] [ 7577.11, 6572.6 ] [ 8084.03, 6071.29 ] [ 8431.38, 5542 ] ]
ASBUILT is an
approximation program.
HP Prime Program: ASBUILT
EXPORT ASBUILT(ma)
BEGIN
LOCAL ml,mx,n,r,l≔{};
// build L
FOR n FROM 1 TO 4 DO
l(n)≔ABS(ma(n))^2;
END;
ml≔list2mat(l,1);
// build A
ma≔2*ma;
ADDCOL(ma,[-1,-1,-1,-1],3);
// compute X
mx≔CAS.LSQ(ma,ml);
// compute radius
r≔√(mx(1,1)^2+mx(2,1)^2-mx(3,1));
// results
RETURN {mx,r};
END;
Example Output: { [ [x0][y0][f]], radius}
{ [ [
5587.37457087 ] [ 4053.99226137 ] [ 37351007.6568 ] ] , 3209.76637679 }
Casio Prizm Program: ASBUILT
“4 × 2 Mat [X,Y]”? →
Mat A
{4 , 1} → Dim Mat B
For 1 → N To 4
Mat A[N,1]² + Mat
A[N,2]² → Mat B[N,1]
Next
2 × Mat A → Mat A
Augment(Mat A,
[[-1][-1][-1][-1]]) → Mat A
(Trn Mat A × Mat A)¯¹
× Trn Mat A × Mat B → Mat C
√( Mat C[1,1]² + Mat
C[2,1]² - Mat C[3,1] ) → R
“RADIUS”
R ◢
Mat C
Example
Output:
[ [
5587.3745555 ] [ 4053.992245 ] [ 37351007.55 ] ]
Radius, R =
3209.766346
Source: Ghilani, Charles D. “Elementary
Surveying: An Introduction to Geomatics”
14th Edition. Pearson. 2014
This blog is
property of Edward Shore, 2016
