## Remote Sensing

- Collection of information without being in contact.

### EM Spectrum in RS

- Near UV: 0.3 - 0.4 micrometer
- Visible: 0.4 - 0.7 micrometer
- IR: 0.7 - 14 micrometer
- Microwave: 0.3 to 300 cm

Visible & IR mostly used.

### How EMR used in RS

- Passive: Energy source from somewhere else (e.g., Sun)
- Active: Self generated beamed energy for reflection (e.g., when sunlight not sufficient or at night)

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- Scattering
- Transmission
- Reflection:
	- Reflectance = \frac{Rs}{I}			[impo]

### NDVI

- For LandSat 8, band 4, 5 [check]
- (5 - 4) / (5 + 4)

#### Procedure

- Import relevant TIF files
- Search and open `Raster Calculator`
- Expression: `Float("LO08_L1TP_137044_20201109_20201120_02_T1_B5.TIF"-"LO08_L1TP_137044_20201109_20201120_02_T1_B4.TIF")/Float("LO08_L1TP_137044_20201109_20201120_02_T1_B5.TIF"+"LO08_L1TP_137044_20201109_20201120_02_T1_B4.TIF")`
- Set color ramp or reclassify

### NDBI (Built-up Index)

- Point of confusion: "chor" may give similar reflectance of building