Understanding Satellite Vegetation Maps

The Vegetation Maps feature on AcreValue offers users access to past and present observations of vegetation and other plant health indicators. These maps are generated using data from the Harmonized Landsat-Sentinel (HLS) satellite imagery project, curated by NASA and the USGS. The data provided is of 30-meter resolution, allowing detailed analysis of property conditions.

How do satellite imagery maps work?

Satellite imagery works by instructing satellites to measure electromagnetic radiation (EMR) that is reflected or emitted from Earth's surface. Sensors on the satellites simultaneously measure data in multiple regions of the electromagnetic spectrum, including visible light, near and shortwave infrared. The range of wavelengths measured by a sensor is known as a band and is commonly described by the wavelength of energy. Bands can represent any portion of the electromagnetic spectrum, including ranges not visible to the eye, such as the infrared or ultraviolet sections.

Each band of an image can be displayed as a greyscale image or combined with other bands to create a color composite image. A color composite image uses three bands, each representing one of the primary colors of light (red, green, and blue), to produce a color image. This combination allows for detailed visualization of different features and conditions on the Earth's surface, such as vegetation, water, and urban areas. Understanding these bands and their combinations helps in isolating various features on the Earth's surface, enhancing property analysis and monitoring.

Satellite Imagery Bands on AcreValue

AcreValue displays a wide range of individual and composite bands. Below is a list of available bands, their wavelength ranges, and applications:

Standard Individual Bands:

• Coastal Aerosol (0.43 - 0.45 µm): Useful for coastal and aerosol studies.
• Blue (0.45 - 0.51 µm): Penetrates water bodies, helps in analyzing aquatic vegetation.
• Green (0.53 - 0.59 µm): Used in vegetation and plant health studies.
• Red (0.64 - 0.67 µm): Sensitive to chlorophyll, crucial for vegetation discrimination.
• Red Edge 1 (0.69 - 0.71 µm), Red Edge 2 (0.73 - 0.74 µm), Red Edge 3 (0.77 - 0.79 µm): Sensitive to vegetation, particularly in monitoring chlorophyll content.
• Near-Infrared (NIR) (0.85 - 0.88 µm): Reflects vegetation vigor, critical for vegetation analysis.
• Narrow Near-Infrared (NNIR) (0.86 - 0.88 µm): Enhances vegetation monitoring.
• Shortwave Infrared 1 (SWIR 1) (1.57 - 1.65 µm): Sensitive to moisture content in soil and vegetation.
• Shortwave Infrared 2 (SWIR 2) (2.11 - 2.29 µm): Similar to SWIR 1, helps in differentiating between types of vegetation and soil moisture.
• Cirrus (1.36 - 1.39 µm): Detects cirrus clouds.
• Thermal Infrared 1 (TIR 1) (10.60 - 11.19 µm): Measures surface temperature.
• Thermal Infrared 2 (TIR 2) (11.50 - 12.51 µm): Similar to TIR 1, used for thermal mapping.

Composite Index Bands:

Composite bands, or band indices, are calculated using ratios between different individual bands. These indices isolate and accentuate specific terrain features.

• NDBI (Normalized Differential Built-Up Index): NDBI = (SWIR−NIR) / (SWIR+NIR). Range: -1 to 1. Higher values indicate built-up areas.
• NDTI (Normalized Differential Tillage Index): NDTI = (SWIR1−SWIR2) / (SWIR1+SWIR2). Range: -1 to 1. Used for detecting tillage practices.
• NDVIre (Normalized Differential Vegetation Index minus Red Edge): NDVIre = (NIR+RedEdge) / (NIR−RedEdge). Range: -1 to 1. Indicates vegetation health.
• NDWI (Normalized Differential Water Index): NDWI = (NIR+SWIR) / (NIR−SWIR). Range: -1 to 1. Higher values represent water bodies.
• GCVI (Green Chlorophyll Vegetation Index): GCVI = (NIR+Green) / (NIR−Green). Range: -1 to 1. Measures chlorophyll content.
• MTCI (MERIS-based Terrestrial Chlorophyll Index): MTCI = (Red−Blue) / (NIR−Red). Range: -1 to 1. Indicates terrestrial chlorophyll.
• SPI (Solar Panel Index): SPI = 0.3 x (2Blue – Red – Green) / (2Blue + Red + Green) + (2SWIR1 – SWIR2 – (0.7xNIR))) / (2SWIR1 + SWIR2 + (0.7xNIR)). Range: -1 to 1. Used in solar panel suitability studies.
• UI (Urban Index): UI= (NIR+SWIR) / (NIR−SWIR). Range: -1 to 1. Identifies urban areas.

Non-Indexed Composite Bands:

These bands are composites used to visualize specific terrain features and can be displayed as color composite images to enhance visualization.

• RGB (Red, Green, Blue): Standard color composite using the red, green, and blue bands. Red Channel = Red, Green Channel = Green, Blue Channel = Blue.
• AGR (Agriculture): Highlights agricultural areas. Red Channel = SWIR1, Green Channel = NIR2, Blue Channel = Blue.
• AP (Atmospheric Penetration): Enhances visibility through atmospheric conditions. Red Channel = SWIR2, Green Channel = SWIR1, Blue Channel = NIR2.
• BE (Bare Earth): Highlights bare soil areas. Red Channel = SWIR1, Green Channel = Green, Blue Channel = Blue.
• CIR (Color Infrared): Combines the infrared, red, and green bands to enhance vegetation analysis. Red Channel = NIR1, Green Channel = Red, Blue Channel = Green.
• FFBS (Forest Fire Burn Scars): Identifies areas affected by forest fires. Red Channel = SWIR2, Green Channel = NIR, Blue Channel = Blue.
• LW (Land & Water): Differentiates between land and water bodies. Red Channel = SWIR2, Green Channel = SWIR1, Blue Channel = Red.
• UE (Urban Environment): Highlights urban areas. Red Channel = SWIR2, Green Channel = SWIR1, Blue Channel = Red.
• VW (Vegetation & Water): Differentiates between vegetation and water bodies. Red Channel = SWIR1, Green Channel = NIR, Blue Channel = Red.

Why the Vegetation Imagery is Helpful

The Vegetation Maps provide significant value to various types of AcreValue users:

• Farmers: Overhead vegetation maps help monitor crop health during the growing season. Farmers can quickly identify areas with poor vegetation growth and apply targeted treatments such as herbicides or fertilizers, optimizing resource use and improving crop yields.
• Timber and Grassland Managers: These maps allow managers to detect low vegetation growth areas, enabling them to prescribe appropriate treatments to boost vegetation.
• Property Developers and Investors: Vegetation maps offer insights into the current state of the property, including past vegetation and crop growth history. Developers can identify areas suitable for development without needing to visit the property, saving time and resources.

Ultimately, the Vegetation Maps facilitate remote analysis and management, providing actionable insights that help users make informed decisions about their properties.

How to Access the Vegetation Maps

To access the Vegetation Maps on AcreValue, follow these steps:

1. Select a property or property sale record on the AcreValue map.
2. Generate a full property report.
3. Navigate to the "Vegetation" tab within the report.
4. Choose the desired image bands and date ranges to view historical and current vegetation data.

These reports, including the Vegetation Maps, can be exported and printed as PDFs, allowing for easy sharing and offline analysis.