LST Calculation Using Landsat 8 Calculator

A specialized tool for calculating Land Surface Temperature (LST) from Landsat 8 satellite data. This calculator uses the single-channel algorithm for accurate scientific analysis.

LST Calculator

Dynamic chart showing LST sensitivity to NDVI changes.

What is LST Calculation Using Landsat 8?

The LST (Land Surface Temperature) calculation using Landsat 8 is a scientific method to determine the temperature of the Earth’s surface from space. It’s not the same as air temperature; LST is the radiative skin temperature of the ground, which is a crucial indicator in various fields like climate science, agriculture, urban planning, and hydrology. Landsat 8, a satellite in the NASA/USGS Landsat program, is equipped with a Thermal Infrared Sensor (TIRS) that measures thermal energy radiating from the Earth. By processing this data, specifically from Band 10, scientists can create detailed temperature maps. This calculator simplifies one of the common algorithms used for this purpose.

LST Calculation Formula and Explanation

This calculator uses a well-established single-channel algorithm to estimate LST. The primary formula is:

LST = (BT / (1 + (λ * BT / ρ) * ln(ε)))

Where the variables depend on intermediate calculations, primarily the estimation of Land Surface Emissivity (ε) from the NDVI.

Description of Variables for LST Calculation

Variable	Meaning	Unit / Typical Range
LST	Land Surface Temperature	Celsius (°C) or Kelvin (K)
BT	At-Satellite Brightness Temperature	Celsius (°C) or Kelvin (K)
λ	Wavelength of Emitted Radiance	~10.8 µm for Landsat 8 Band 10
ρ	Constant (h * c / σ)	~14388 µm K
ε (Emissivity)	Land Surface Emissivity	0.95 – 0.99 (unitless)
Pv	Proportion of Vegetation	0 – 1 (unitless)
NDVI	Normalized Difference Vegetation Index	-1 to +1 (unitless)

Practical Examples

Example 1: Temperate Forest Area

A dense forest area will have a high NDVI, which affects its emissivity and final LST.

• Input Brightness Temperature: 20 °C
• Input NDVI: 0.7
• Resulting LST: Approximately 21.53 °C

Example 2: Arid Urban Area

An urban area with little vegetation has a low NDVI, leading to a different emissivity value.

• Input Brightness Temperature: 35 °C
• Input NDVI: 0.15
• Resulting LST: Approximately 37.89 °C

How to Use This LST Calculator

1. Enter Brightness Temperature: Input the Top of Atmosphere (TOA) Brightness Temperature value obtained from Landsat 8 Band 10 data. This should be in Celsius.
2. Enter NDVI: Provide the Normalized Difference Vegetation Index for the same location. This value is critical for estimating the surface’s emissivity.
3. Review Results: The calculator will instantly provide the final LST in Celsius. It also shows the intermediate values for Proportion of Vegetation (Pv) and Land Surface Emissivity (ε) so you can understand the calculation.
4. Analyze the Chart: The dynamic chart visualizes how LST changes as NDVI varies, keeping the brightness temperature constant. This helps in understanding the strong influence of vegetation cover on surface temperature.

Key Factors That Affect LST Calculation

• Vegetation Cover (NDVI): Densely vegetated areas tend to have lower LST due to evapotranspiration. This is the most significant factor in the emissivity calculation.
• Soil Moisture: Wet soil has a higher thermal inertia and can appear cooler than dry soil.
• Land Cover Type: Urban materials like asphalt and concrete absorb and retain more heat than natural landscapes, leading to the Urban Heat Island effect.
• Atmospheric Conditions: Water vapor and aerosols in the atmosphere can affect the radiance received by the satellite, requiring atmospheric correction for precise measurements.
• Sun Angle and Season: The time of day and year impact the amount of solar radiation received by the surface, directly influencing its temperature.
• Surface Emissivity (ε): This property determines how efficiently a surface radiates thermal energy. It is a key variable that this calculator estimates based on NDVI.

Frequently Asked Questions (FAQ)

1. Where do I get the input values?

The input values (Brightness Temperature and NDVI) are derived from processing raw Landsat 8 satellite imagery using GIS software like QGIS or ArcGIS, or platforms like Google Earth Engine.

2. Is this calculator 100% accurate?

This calculator provides a very good estimation based on a standard algorithm. However, for research-grade accuracy, a full atmospheric correction using tools like MODTRAN is often required.

3. Why does NDVI affect LST?

NDVI is used to estimate the proportion of vegetation, which in turn helps determine the land surface emissivity. Different surfaces (vegetation, soil, water) emit thermal energy at different efficiencies.

4. Can I use this for other satellites?

No. This calculator is specifically parameterized for Landsat 8’s TIRS Band 10. Other satellites have different thermal bands with different wavelengths and require different constants.

5. What do negative NDVI values mean?

NDVI values below zero typically correspond to water bodies. Values close to zero represent barren land, sand, or snow.

6. What is “Brightness Temperature”?

It is the temperature of a surface as measured by the satellite sensor without any correction for surface emissivity. It’s an intermediate value used to calculate the actual LST.

7. Why is LST important?

LST is a key indicator of the Earth’s energy balance and is used to monitor drought, predict agricultural yields, analyze urban heat islands, and study climate change.

8. What is the unit of the constant ρ (rho)?

The constant ρ is a combination of the Planck constant, speed of light, and Boltzmann constant, and its value is approximately 14388 µm K.