NGR

This false-color image can also be referred to as a summer forestry false-color image. The abbreviation NGR in the false-color image hints at the spectra it contains. It combines reflected near-infrared radiation (NIR), green light (Green), and red light (Red). Thus, the near-infrared information is placed in the red channel, green visible light in the green channel, and red visible light in the blue channel.

This map layer can be viewed year-round but is perhaps most useful and informative during the period of active vegetation. Figure 1 visualizes the changes in this color tone throughout different seasons. Generally, we see how in early spring the map layer appears in blue tones, bright orange and brown tones appear as summer approaches, and with autumn and cold, the orange and brown colors fade to bluish-gray alongside withering vegetation. When the ground is bare in winter, a bluish-gray background remains, but after snowfall, the map layer becomes whiter and duller. Snow appears in this false-color layer as a familiar white tone, whereas ice without snow on water bodies appears in light blue tones.

Figure 1. NGR false-color image during different seasons, from top left: spring, summer, autumn, winter.

Chlorophyll in plants reflects near-infrared and green light well. Since deciduous trees reflect near-infrared radiation more intensely than conifers, they are easy to distinguish by color. Near-infrared placed in the red channel thus highlights deciduous forests appearing as textured dark orange, while coniferous forests are dark green. Hence, the NGR image provides a good overview of forest composition (Figure 2).

Figure 2. Differentiation of deciduous and coniferous forests in Satiladu’s NGR false-color image. State forest boundaries are enabled.

If you are familiar with forestry orthophotos, the NGR false-color image applies a very similar tonality (Figure 3). Both forestry and regular up-to-date orthophotos can be viewed in Satiladu from the left menu under "Orto." The high-resolution orthophoto layer can be activated, for example, when you notice something unusual on the satellite image but cannot identify it due to resolution limits. When comparing satellite images to orthophotos, keep in mind that orthophoto flights and the satellite image may not be taken simultaneously. Satellite images have lower resolution but provide more frequent updates about landscape and vegetation changes than high-resolution orthophotos.

Figure 3. Forestry orthophoto (left) and summer forestry satellite NGR image (right) from the same location.

Bright orange colors also appear on open green areas, meadows, and uncut fields. Common semi-natural community types in Estonia include wooded meadows, alvars, coastal, floodplain, forest, and peat meadows, as well as wooded pastures. These areas do not have the forest texture in satellite images but appear as a uniform, smooth, bright orange surface (Figure 4). Therefore, it is a good idea in Satiladu to use the open area mask for studying fields and various open areas (like meadows), and the forest mask to distinguish forest blocks.

Figure 4. Spring view of managed meadows along the Kasari and Vigala rivers, displayed in bright orange (reference to Satiladu).

When observing forests, you can optionally enable vector layers related to forests. For example, it is possible to view boundaries of state or private forests (Borders > Private Forest / State Forest), boundaries of areas with logging restrictions established by the general plan (Borders > Protected Forest), or forest registry logging notifications (Borders > Notifications). A logging notification is an official document required to be submitted to the Environmental Board when the forest landowner intends to carry out logging.

In the summer forestry satellite image, clearcuts and forest openings, mowed meadows, and plowed fields appear light blue. Figure 5 shows a forested area together with the forest registry logging notification vector layer. Through this, the satellite image helps indicate where clearcut logging has been planned and completed (light blue), is ongoing (partially blue), or has not yet been conducted. Explanations about the abbreviations of planned logging types shown with the vector layer (e.g., LR, HR, etc.) can be found in Satiladu’s legend info bubble (Figure 6).

Figure 5. Summer forestry satellite image with forest registry logging notification vector layer showing, for example, where planned clearcut logging has been carried out.

Figure 6. Information on vector layers, such as logging notifications, can be found in Satiladu’s legend menu under the info icon.

Drained peat fields and wetland vegetation often appear in cold tones on the NGR satellite image (sample reference Satiladu), ranging from bluish-green to grayish blue. Peat fields are often recognizable by their characteristic streaky texture and linear boundaries in satellite images (Figure 7). Drained peat fields are fire hazardous because dried peat ignites easily. Satellite images can highlight drier areas.

Figure 7. Peat fields of Keskküla bog near Laiküla (reference to Satiladu).

Clean water bodies absorb light well across the entire observed spectral range, appearing black on satellite images. However, if vegetation grows in the water or there is dense shore vegetation, it appears greenish on the NGR image (Figure 8). The coloration of water bodies is also affected by sediments or turbidity, which increase light scattering. When observing water bodies, we recommend disabling the Hybrid layer in the lower-left corner.

Figure 8. From top to bottom, water bodies: Kaiavere, Raigastvere, Elistvere, Soitsjärv, Saadjärv (reference to Satiladu).

Unlike water bodies, which appear black or greenish, artificial surfaces stand out in light blue colors on satellite images, providing clear contrast to natural areas. This distinction is especially useful for identifying human-made infrastructure, such as roads, buildings, and other artificial surfaces, which stand out from water bodies and other natural objects (Figure 9).

Figure 9. Artificial structures in Pärnu city—buildings, roads, and facilities—appear in light blue.