# Regular Meeting (2020.2.17)
## Completed

* Ubderstanding what *Hough Transform* is

## Doing now

* How Hough-Transform worked in 2D-Tracker

* Testing GTY transceiver(Some parameter I don't know how to setting)

## The Hough Transform

**Normal usage of Hough Transform**

**Used in Tracker on Belle-II**


### Space

#### 1. x-y Space
$f(x,y)$ => $y = ax + b$
$a$: slope
$b$: intercept

if we fixed $a = 0.5, b= 4.5$

chart of $y = 0.5x + 4.5$


#### 2. a-b Space

$g(a,b)$ => $b = -ax + y$

if we fixed $x = 0.5, y = 4.5$

=> $b = -0.5a + 4.5$

chart of $b = -0.5a + 4.5$


(slope = $-a/b$ = tan($\theta$))

#### 3. Represent a-b Space with r-$\theta$ Space

h(r,$\theta$) => r = xcos($\theta$) + ysin($\theta$)


if we mapping a linear eq.(a-b space) to r-$\theta$ space


### 4. Accumulator with r-$\theta$ Space



#### folw of Hough Algorithm r-$\theta$ Space

1. Filtering input data or image(not found in paper)
2. Calculating (r,$\theta$) for each point which stayed after step 1
3. Choosing (r,$\theta$) with threshold
4. Rebuilding line with (r,$\theta$)

###### tags: `Regular Meeting` `DeWei`