sline_results Structure

Source: product.h


Byte	Size	Contents
0	SINT4	East coordinate of center point (cm)
4	SINT4	North coordinate of center point (cm)
8	BIN4	Rotation angle to X-Y coordinates of curve fit polynomial Span is -90 ... +90°.
12	SINT4	X coordinate of left of curve (cm)
16	SINT4	X coordinate of right of curve (cm)
20	SINT4[6]	6 polynomial coefficients
44	SINT4	Standard deviation of fit
48	SINT4	Propagation speed (mm/second)
52	BIN4	Propagation direction (binary angle)
56	SINT4	Reference side wind speed (mm/second)
60	BIN4	Reference side wind direction (binary angle)
64	SINT4	Other side wind speed (mm/second)
68	BIN4	Other side wind direction (binary angle)
72	SINT4[32]	ETA in seconds for each protected area (0 if in area, -1 if unexpected)
200	UINT4	Flags: Bit0=Propagation speed available Bit1=Wind speeds valid
204	796	`<spare>`

The polynomial curve fit is calculated as follows:

Threshold a shear product based on the shear threshold specified in the product configuration.

Let East and North refer to the distance of the center of each pixel from the radar position in centimeters. This coordinate system is rotated by an angle θ clockwise about the radar location to produce a new coordinate system with distances also in centimeters. This is the Rotation angle to X-Y coordinates of curve fit polynomial. This coordinate system uses the variables X and Y. The equations for the transformation are:
```
X = Northsinθ + East cosθ
Y = Northcosθ – East sinθ
```
This transformation is T_rotate, and the reverse transformation isT^-1_rotate.

In this coordinate system, the X-coordinate of the left most end of the line is X_l and the right most end X_r.
Shift and scale the coordinate system to keep the polynomial coefficients from becoming too large. The equations for the transformation are:

$X' = \frac{X - X_{l}}{X_{r} - X_{l}}$

Call this transformation T_scale, and the reverse transformation T^-1_scale.

In this new coordinate system, the polynomial is expressed as:
```
Y' = A₀ + A₁X' + A₂X'² + A₃X'³ + A₄X'⁴ + A₅X'⁵
```
or
```
Y' = P[X']
```
The standard deviation is computed as follows: Let [X'_i,Y'_i] represent the i^th point in the data set in the rotated and scaled coordinate system, and N the total number of points, then the standard deviation is:

$s t a n d a r d d e v i a t i o n = \sqrt{\frac{1}{N} \sum_{i = 1, N^{{[{Y'}_{i - P} {[{X'}_{i}]}_{}]}^{2}}}^{}_{}}$

The center point is computed as follows: Let [East_i,North_i] represent the i^th point in the data set in the original coordinate system, and N the total number of points:

$E a s t c e n t e r = \sqrt{\frac{1}{N} \sum_{i = 1, N^{{E a s t}^{}_{i}}}^{}_{}}$

$N o r t h c e n t e r = \sqrt{\frac{1}{N} \sum_{i = 1, N^{{N o r t h}^{}_{i}}}^{}_{}}$