Implement decaying D8 flow accumulation #389
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…/386-add-decaying-flow-accumulation Conflicts: HISTORY.rst
| cdef struct DecayingValue: | ||
| double decayed_value # The value, which will be progressively updated as it decays | ||
| double min_value # The minimum value before the Decaying Value should be ignored. | ||
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| cdef struct WeightedFlowPixelType: |
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I noticed the other struct definitions have a few comments above to describe them. Should these follow that same convention?
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Yep, great catch! Patched in 4f0e062
| int xi | ||
| int yi |
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The other struct definitions use unsigned int for pixel location, any reason not to do that here as well for consistency?
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Nope! In fact they really should be unsigned ints for consistency with the way indexes are used elsewhere in the function. Patched in d645b70
| # Search the block for root pixels. | ||
| # A root pixel is a flow direction pixel that is nodata, which means it | ||
| # may be a drain just off the edge. |
| double decayed_value # The value, which will be progressively updated as it decays | ||
| double min_value # The minimum value before the Decaying Value should be ignored. | ||
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| cdef struct WeightedFlowPixelType: |
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I think that this replaces ALL instances of FlowPixelType. Should we remove that struct definition?
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Interestingly, I'm still seeing FlowPixelType used in flow_accumulation_mfd, so I think it makes sense to leave it here for now.
This PR copies the modifications to D8 flow accumulation implemented for the NCI Water Quality project that allow for pixel loads to decay as they pass over the landscape. You could think of like a pollutant flowing across the landscape, where some fraction is absorbed due to landcover or some other factor.
Tests have been implemented and runtime should only trivially be affected when decaying accumulation is not in use. When decaying accumulation is used, there is an extra cost in memory and in iteration over the pollutant contributions to the pixel.
Fixes #386