NGP

This false-color image can also be referred to as a land cover type false-color image. It combines near-infrared radiation (NIR), visible green light (Green), and red light (Red). Specifically, NIR data is mapped to the red channel, green light data to the green channel, and red light data to the blue channel of the visible spectrum.

Figure 1 visualizes the changes in color tones across different seasons. Generally, in early spring, the map layer appears in bluish tones. As summer approaches, it becomes more colorful as different land cover types emerge. In autumn and with the onset of colder weather, the colors blend back into bluish hues as vegetation withers. During winter, when the ground is bare, the bluish tone remains, but when snow covers the ground, the map layer shifts to vibrant greens and yellows. Snow appears yellow on this false-color layer, while open water bodies without ice take on a bright green tone.

Figure 1. NGP false-color views across seasons. From top left: spring, summer, autumn, winter.

Chlorophyll in plants reflects both near-infrared and green light well. The near-infrared data is displayed through the red channel, and the green light data through the green channel. Healthy vegetation typically has a low NDPI value, represented in this spectral combination through the blue channel. High values in the red and green channels (and low values in the blue channel) give healthy vegetation yellow and orange tones (Figure 2).

Dark orange and pinkish tones indicate areas with high chlorophyll content and low NDPI values. These include unmown fields and deciduous trees. Coniferous trees, which reflect slightly less near-infrared radiation than deciduous trees, appear dark green in the images (Figure 3). However, due to exceptions, areas should always be analyzed in greater detail to draw specific conclusions.

Figure 2. On the left, the NGP false-color image highlights healthy vegetation in orange and yellow tones; on the right, a comparison with the vegetation index (NDVI).

Figure 3. On the left, coniferous forests appear dark green, while deciduous forests are lighter textured pinkish-orange. On the right, a forestry orthophoto for comparison.

Wetlands and peatlands are well distinguished in NGP images. Satellite imagery taken in late spring or summer shows these areas as soft blue tones compared to their surroundings (Figure 4). These areas reflect little green light and near-infrared radiation and have high NDPI values, which add a blue tone when displayed through the blue channel.

Figure 4. Wetlands and peatlands stand out in soft blue tones, with the Satilao sub-1m mask activated (reference to Satilattu).

Mowed grasslands and plowed fields appear lighter blue. Bare soil surfaces have high NDPI values, represented through the blue channel in this spectral combination. The color of fields with sparse vegetation varies from green to light blue, depending on the proportion of vegetation and soil (Figure 5).

Figure 5. Plowed fields and areas with minimal vegetation appear in blue tones (left). On the right, an RGB image for comparison.

Water bodies have low NDPI values. They also absorb near-infrared radiation effectively and reflect only a small amount of green light, which is why water bodies appear dark green or black in the image. The NGP combination also highlights features such as flooding (Figure 6).

Figure 6. Spring flooding along the Emajõgi River (reference to Satilattu).

Clouds reflect both green light and near-infrared radiation, with low NDPI values similar to water bodies. As a result, clouds appear yellow in the image, as does snow. Note that cloud edges are visible in this spectral combination as bright green tones (Figure 7).

Figure 7. Cumulus and cirrus clouds in the NGP spectral combination.