# Lab 2
`Contributer: TA, Zhixin (Another TA)`
## Mean, std, residual

## 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
or when variables are independent:
### 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

### GPS logger for Android phones

### ArcGIS pro
- Import GPX
- Project GPS file:
- Use Project function in geoprocessing

- Add x,y,z
- 
- 
- Make sure you choose double
- 
- Export to csv and do the rest of jobs