Why did we change it? How does the new color map work?
Thermal imagery provides reliable temperature data across different regions, soils, and plants over the entire growing season. Make that information easy to understand is more difficult than it seems. When TerrAvion display any thermal map, one of two factors has to be prioritized: temperature precision and ranged variation. TerrAvion wants to display precise temperature variations throughout the year; however the more precise the temperature, the smaller the the range variation.
The temperature range of this field in early May was 72-83°F (an 11° spread) around 3 PM. The image is mostly a dark red color, which indicates warm temperatures on our scale.
A month later, the same field was 92-109° (a 17° spread) at 12:30 PM. The image is colored bright orange, indicating the field is hotter than prior, according to our scale.
A constant scale produces colors that are always meaningful: purple is cold and yellow is hot. However, a ranging scale is useful is displaying variations across the field despite the temperature relative to the rest of the season.
The two images above are from the exact same data and time, but are shown in different color scales. In the image on the left, the colors are kept constant like the earlier images. Switching to a different color scale, as shown in the image on the right, shows a lot of variation , although the actual temperature spread is only 10 degrees.
However, if the fine-tuned color scale for the same field is used a month later, there is no variation in colors, because the temperatures are too far off the scale.
Fine-tuning thermal images for each field at every point in the growing season, creates another problem: the colors are not useful when comparing to any other fields or historical images.
In the image on the left, the dark purple, near the center of the field is 86°F, but in the image on the right, it's 98°F. Furthermore, the blue, which indicates a higher temperature, is 91°F on the left, but 108°F on the right.
When looking at two different fields, this problem becomes even more pronounced.
In the field on the left, the black color, which is colder than purple, is 103°F while the purple on the right is already 98°F. If you were looking at several fields at once, what might seem like a 'hot spot' in one field might just be slightly warmer in another. Furthermore, a field that is really hot, might look normal temperature because the thermal scales are fine-tuned per field.
When designing our thermal maps, we wanted to show important variations that would not create any confusion. Therefore, TerrAvion has chosen to provide consistent colors over the whole season, while displaying enough variation to spot significant problems.