Blue Earth Imaging takes aerial photography beyond simple color images and makes use of light that is invisible to the human eye. This acquisition of information about the properties of different objects and phenomenon is called Remote Sensing. Remote Sensing allows significantly more information to be obtained about an area than with color imagery alone. Particularly, vegetation tends to absorb most visible light in the process of photosynthesis, but it reflects most infrared light. This characteristic of photosynthesizing organisms allows many characteristics to be observed that would otherwise be invisible.
*Images below can be enlarged by clicking on them. They will also show a color version for reference by dragging your pointer over the image.
Imagery is also typically georeferenced for viewinhg in our online mapping application. Click here for more information on Georeferenced Image Formats.
Raw Image Formats Overview
Blue Earth Imaging collects two types of unprocessed imagery - Color (RGB) and Color Infrared (CIR). These images are only processed for color and contrast, to correct for ambient sunlight variations.
Color (RGB) Imagery
Color imagery consists of Red, Green and Blue light, and therefore is often referred to as RGB imagery. This is also how your eye sees the different colors in light, so it is very useful for comparing to processed imagery in order to understand what is happening in the processed image.
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Color Infrared (CIR) Imagery
Color Infrared film was originally developed to detect camouflage for the military after World War II. Camouflage would appear very dark, surrounded by bright red vegetation. Color infrared film is sensitive to infrared light that has a wavelengths slightly longer than visible light. This infrared light then becomes the red channel in CIR imagery. Vigor has been interpreted in traditional CIR imagery by subjectively judging the relative brightness of the shade of red in an image. The deeper, the red, the more vigorous the growth in a crop. As can been seen in the image below, vegetation can even be located in areas that look like soil in the RGB image.
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Processed Image Formats Overview
To gain the maximum benefit from Remotely Sensed imagery, the data must be processed into image formats that allow analysis that cannot be accomplished with the raw imagery. The analysis can yield information about vegetative health, land cover, and changes over time.
Normalized Differential Vegetative Index (NDVI)
The Normalized Differential Vegetative Index is calculated using the following equation with the Infrared and Red image bands.
NDVI images show the difference between the brightness of the red band and the infrared band. Vegetation is much brighter in the red band than infrared band and therefore will have positive values for NDVI. Water is much brighter in the red band than the infrared band and will have negative values for NDVI. Soil, concrete, asphalt and other materials tend to have NDVI values near 0. When evaluating the NDVI of vegetation, higher values will indicate more vigorous growth. By applying a color map to these values, as seen below, NDVI can be presented in a way that highlights specific features.
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NDVI HD
NDVI HD is a custom imagery product, provided exclusively by Blue Earth Imaging. NDVI HD imagery highlights vegetation and suppresses other information that tends to clutter the image. The vegetation with the least vigor is colored Red while areas with high vigor are colored darker shades of green. This allows instant identification of areas that are progressing the best or other areas that may have problems.
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Fraction of Photosynthetically Active Radiation (FPAR)
The Fraction of Photosynthetically Active Radiation (FPAR) is a measurement of the ratio of area that is photosynthetically active, such as a leaf, versus area that is photosynthetically inactive, such as soil. FPAR can help to determine overall leaf density which is often closely related to crop yield. In crops that do not have 100" ground coverage, FPAR can show growth trends that do not appear in the NDVI image.
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Change Detection
Change Detection imagery requires images collected at two different dates. The NDVI of the more recent image is compared to the older image to see how the vigor has changed over time. Increases in vigor are colored darker shades of green, while decreases in vigor are colored yellow and red. An NDVI image may show some areas of a field to be stressed, but a change detection image may reveal that those areas are progressing well and thereby eliminate the need for further investigation.
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Color Variation
Color Variation imagery shows how the color changes in an area. For agricultural applications, color would be expected to be very uniform, indicating that all the plants are growing in the same way. As the color varies, this can indicate nutrient deficiencies, invasive species and weeds. In the case of weeds, the vigor of a weed is often very similar to the crop, so a NDVI image would show uniform stress. A color variation image may show subtle differences in the colors of the weed so it can be treated effectively and contained without causing damage to areas of the field without the infestation.
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