Dear Sir, I am very happy if you clarify my doubts regarding habitat quality model:
*First, I initially run habitat quality using the default Half-saturation Constant (0.05) to see the highest grid-cell degradation level. However, the “quality” image and Deg_sum image shows the reverse as compared to the real habitat quality. The value of “quality” image was highest in crop land and urban area but very low in forest land. Could you clarify why? After I set Half-saturation Constant 0.5 (i.e., 0.9/2), the quality image looks good as I evaluated it based on known habitat locations on the ground.
Second, the habitat quality result creates a kind of circular feature around the urban area, similar to point interpolation. The radius of the circle was the same as the maximum distance I put in the CSV file. Can I avoid circular visualization?*
*Third, could you clarify the importance of output images in the “intermediate” folder?
Hi @Eshetu , thank you for your questions, sorry for the delayed response. Which version of InVEST are you using? Can you please share the log file from the output workspace?
This model had some significant changes added in version 3.13.0, specifically related to the distance decay functions. The changes are described as follows,
The model now uses an euclidean distance implementation for decaying
threat rasters both linearly and exponentially. Since InVEST 3.3.0 a
convolution implementation has been used, which reflected how
the density of a threat or surrounding threat pixels could have an
even greater, cumulative impact and degradation over space. However, this
was never properly documented in the User’s Guide and is not the approach
taken in the publication. The convolution implementation also produced
degradation and quality outputs that were difficult to interpret.
Dear Prof. Dave, thank you so much for your reply. Attached herewith is the log file from the output workspace. I used version3.13.0. What still persists is a circular feature around the urban area in habitat quality output, similar to interpolation mapping. The remaining questions were resolved.
Hi @Eshetu , it sounds like upgrading to version 3.13.0 solved some of the problems, that’s good!
I can’t say for sure without seeing this, but this circular feature sounds like an expected outcome. The model is using a distance decay function to map the impact of a threat on the surrounding landscape. The impact will be greatest near to the threat, and then less as distance increases in all directions, forming a roughly circular impact zone. Does that agree with the quality results you see?