Foliage Crown Factor

Glenn Morvan

Dear Community,

In the Tygron wiki, the foliage crown factor is explained as the ration between the length of a tree and the radius of the crown. In case of standard deciduous trees this factor is 0,75 which would mean that a tree of 5m has a crown radius of 3,75m and a diameter of 7,5m.

For a standard deciduous tree, this crown diameter seems to large. Could it be that the crownfactor is in fact the ration between the diameter of the crown and the length of the tree instead of the radius and the length?

Keen to hear from you.

Kind regards,

Glenn

Glenn Morvan

Link to wiki: https://support.tygron.com/wiki/Foliage_crown_factor_(Heat_Overlay)

Hansje

Hi @Glenn Morvan ,

Maybe this wiki link can help you understand the foliage crown factor that is been used in teh Tygron Platform better.

Foliage height calculation model (Heat Overlay) - Tygron Support wiki

Here the explanation is given on how the factor is calculated.

Per type of tree the factor can be adjusted. So maybe that is also something to think about. To make sure you select the correct type of tree?

Glenn Morvan

Hi @Hansje ,

Thanks. So it is the ration between height and diameter. That seems logical :).

In that case, just a suggestion to adjust the explanation in the other wiki page about foliage crown factor (https://support.tygron.com/wiki/Foliagecrownfactor(HeatOverlay)) for other users. There it says Radius.

Kind regards,

Glenn

vincent.rd

Dear @Glenn Morvan,

The Foliage Crown Factor is based on the ratio between foliage height and foliage radius (NOT the foliage diameter). Just to be sure, I confirmed this just now with our R&D department.

If you find that a default value for a function is not in accordance to your own data, you can always adjust the value in the function values table.

I hope this answers your question.

Regards, Vincent

Glenn Morvan

Dear Vincent,

In that case, as mentioned in the first post, that would mean that a tree of 5m with a foliage crown factor of 0,75 (factor for Standaard Loofboom) has a diameter of 7,5 meter (larger than the length). That doesn't seem to make sense and is contradictory with the explanation that Hansje sent me in her first reaction (Foliage height calculation model (Heat Overlay) - Tygron Support wiki) which says the following:

It also seems that trees in Tygron with a factor of 0,75 have a diameter that is smaller than the length in the design. Lastly, I have computed the shade of a 21m tree with Tygron giving a shade surface of approx. 350m2. Given a 21m meter tree with a radius of 15,75m the shade surface would have to be at least the surface of the crown of 780m2 (Pi * 15,75^2 = 780). In this calculation a tree radius of 7,8m (diameter of 15,75m) gives a more realistic figure of the crown surface of 200m2 in order to yield the computed shade surface of 350m2.

I hope you can follow my reasoning :). In short, to me it seems more logical in multiple ways that it is the ratio between height and diameter, but if this is surely not the case, I will adjust my models accordingly.

Keen to hear from you.

Kind regards,

Glenn

vincent.rd

Dear @Glenn Morvan,

Although I can easily find images in Google of deciduous trees that have wider crown diameters then their height, I have sent your question forward to R&D. I understand how you come to your question and there is some ambiguity in how this is documented on our end.

I will get back to you when I have feedback from R&D.

Best regards,

Vincent

vincent.rd

Dear @Glenn Morvan,

We have finally found the source of the confusion, diameter is indeed the parameter to work with!

The diameter is derived from multiplying the tree height with the foliage crown factor. Each grid cell stores tree height and radius. In the background the radius is multiplied by 2/ the diameter is divided by 2 to work with foliage. In the source code the cell uses radius, while the calculation uses diameter, hence the contradiction.

There is no sound scientific base for this calculation, as mentioned before, but I hope the clarification from above will answer your question.

A more (scientific) accurate approach would be to use (foliage) areas or grid, if that data is available.

We have adjusted the documentation accordingly, which we will update on the LTS support wiki after final review.

Thank you very much for bringing this question to our attention!

Kind regards,

Vincent

vincent.rd

Dear @Glenn Morvan,

Both wiki pages are corrected too now:

'https://support.tygron.com/wiki/Foliage_height_calculation_model_(Heat_Overlay)#Functions'

and

'https://support.tygron.com/wiki/Foliagecrownfactor_(Heat_Overlay)'

Kind regards,

Vincent

Glenn Morvan

Dear Vincent,

Thanks a lot for this clarification. Glad I could help :).

Kind regards,

Glenn