---
# System prepended metadata

title: Regular Meeting (2020.2.17)
tags: [Regular Meeting, DeWei]

---

# 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**
![hough-result](https://i.imgur.com/HYWt6I6.png)

**Used in Tracker on Belle-II**

![b2dtrc](https://i.imgur.com/cwiSHiM.png)

### 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 $y = 0.5x + 4.5$

![xy-space](https://i.imgur.com/jWqH7Pt.png)

#### 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 $b = -0.5a + 4.5$


![ab-space](https://i.imgur.com/JqrzkCW.png)

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

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

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

![r-th](https://i.imgur.com/uCTAxu3.png)

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

![th-xt](https://i.imgur.com/XVO8edR.png)

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

![acc-1](https://i.imgur.com/4nz9QbX.png)

![rotate](https://docs.opencv.org/3.4.9/houghlinesdemo.gif)

#### 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`