4- WARNING MESSAGES


 

The model will show some messages if a value is out of range, or if a calculation is not done correctly. If the model is not able to compute your request, please contact us.


 

When using the model from compiled code, warning  messages may look like this: "BRDF may not be calculated correctly (PG at vza = 86.0 deg.)"

This message is sent when outside the range of valid qv, usually this happens because the gap fraction and the hotspot use a slightly different approach to compute the gaps in the canopy so that PG can sometime be greater than Pvg at large qv. To solve this problem, parameters such as Ws and Wt may need to be changed,  depending on the LAI,  etc.

On the NT/95/98 version, a message box like this appears when there is a problem: 

 

The Warnings are: 


 

Warning 1:Problem with the Neyman tree distribution; the sum of all probability is less than 0.99.
Solution: Change the values of n. The following figures shows how the Neyman grouping affects the probability of having trees in a quadrat:

Warning 2: Warning in ground proportion; the gap fraction is smaller than the probability of seeing the sunlit ground.
Solution: Although the computation may not be as accurate, this error usually does not induce a large error on the reflectance. 

Warning 3:Warning in tree crown proportion; the crown closure (1-Pvg) is smaller than the probability of seeing sunlit crowns.

Warning 4:Warning Repulsion not correctly set; it may be too large.
Solution: set the repulsion index to zero, or to a small fraction,  since the total crown area you specified is larger than the ground surface. 

Warning 5:Warning in multiple scattering scheme.
Contact us if you have this problem. 

Warning 6:Warning Problem with Omega Total.

Warning 7: Warning Problem with repulsion function Fr.
Solution: usually you need to set Fr to 0 to allow no overlapping. This warning tells you that you have too many trees for allowing no overlap of tree crowns.

Warning 8: Warning Problem with Q1.

Warning 9: Warning Problem with Q2.

Warning 10: Warning Problem with Hotspot kernel.

Warning 11: Warning Problem with fd3 (nadir function).

Warning 12: Warning Problem with Nadir function (Zg>Pvg).

Warning 13: Pvg < 0 Gap Fraction is negative. 
This problem should not happened anymore.

Warning 14:Q1 < 0 in multiple scattering scheme (q1_ms.c) 

Warning 15: Problem with hyperspectral mode (r>1)

Warning 16:Q1 > 1 in multiple scattering scheme (q1_ms.c) 
This happens for low foliage density crowns.

Warning 17: Pti is out of bound (either Pti>1 or Pti< 0)
Note this is a problem that should never happens, it is more a debugging
tool than a real warning.

Warning 18: Problem with Repulsion function parameter

Warning 20: Crown projection is larger than quadrat surface


 

When using the "No Warning" option, the warnings won't appear during the simulations, but they can be seen with the view flip button.