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# System prepended metadata

title: Lab 2

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# Lab 2
`Contributer: TA, Zhixin (Another TA)`
## Mean, std, residual
![](https://i.imgur.com/BiM4m9y.png)


## Outlier detection
- Step 0: Say it loud that you assume the error distribution is normal distribution.
- Step 1: Calculate the mean and standard deviation of all data.
- Step 2: Compute mean+2*std, mean-2*std
- Step 3: Identify data beyond mean+2*std and mean-2*std
- Mean= most probable value in normal distribution
    - When the number of samples is big enough, the mean of samples will be equal to true value.
    - We never know if the number is big enough or not.

## Error propagation
### Formula
![](https://i.imgur.com/4xZxOO0.png)
or when variables are independent:
![](https://i.imgur.com/vTGsoGw.png)
### Steps
- Step 0: check (or assume) if the variables are linear dependent. 
- Step 1: Write the equation, such as f(x,y)=2x+3y
- Step 2: Use error propagation formula

## Q1 
### Mytracks for iphones
![](https://i.imgur.com/OeQCj51.png)
![](https://i.imgur.com/7Lpmd6u.png)

### GPS logger for Android phones
![](https://i.imgur.com/WXoJW7g.png)

### ArcGIS pro
- Import GPX
![](https://i.imgur.com/cfvdjP0.png)
- Project GPS file:
    - Use Project function in geoprocessing

- Add x,y,z
    - ![](https://i.imgur.com/C1B3ptS.png)
    - ![](https://i.imgur.com/ubJ4LNM.png)
    - Make sure you choose double
    - ![](https://i.imgur.com/HLaOqFY.png)
- Export to csv and do the rest of jobs

