The ImRa-system can be used to detect the internal differences in humidity and density conditions of a living tree. The radar measurement does not harm the tree at all. It is an easy method to control the condition of a tree. The 1 GHz antenna is the most suitable for tree diagnostics.
In living trees there exists always humidity and density variations, which generate radar reflections. If a tree is healthy and normal, then the reflections remain about constant when the antenna is moved along the trunk. The radar profile is regular and the reflections can be seen as continuous straight lines. Rot and other damage, in the tree, generate variations to the radar profile. The reflections are stronger or disappear, when measured from one point to another, along the trunk. The radar profile shows broken or curly echo lines or there can exist very clear extra lines.
Two profiles of the same birch (Betula pubescens): Spring
The diameter near ground was about 50cm. The measurements are made along the trunk from the base upwards, in these profiles the antenna has been moved along the left side of the profiles.
The profile on the left is measured in early spring (in Finland), when the tree was still resting. The profile on the right is measured later, at the end of April, when the tree was preparing for leaves and growing season. The flow of the organic fluids can be seen as intensive reflections inside the bark (the right profile, diameter scale 5.15 cm).
The profile shows a rotten spruce.
The profile shows a healthy spruce.
The profiles show the measurements of two spruces. The measurements are made along the stem downwards to the base, in these profiles the antenna has been moved along the right side of the profiles.
The profile on the left shows a rotten (Heterobasidion annosum) tree. The rotten heart of the spruce can be seen in the profile in diameter scale between 10...20 cm, where the rotten part gives strong echoes.
The profile on the right shows a healthy spruce. The bending of the echo-lines is caused by thickness variations due to the large roots. Both spruces are Scandinavian species, Picea abius.