Manual
The manual covers two sections. Firstly the workflow will be covered. This includes a discussion of the calculations and formulas. This is so that a user can understand how the CPLUS processing workflow and calculations for each step are done when processing the pathways and carbon layers, how the activities are created, algorithms applied to create the priority weighted layer (weighted activity), and the last step, which is the highest position calculation.
The second section offers a succinct overview of each step, providing references to detailed explanations for further clarification. A description of the generated report is also provided.
CPLUS calculations and formulas
Figure 1 shows the workflow of the CPLUS model. The workflow can be split into four parts:
- Natural climate solution (NCS) weighted carbon pathway(s)
- Activity
- Priority weighted layer (Weighted activity)
- Highest position (Scenario result)
Figure 1: CPLUS workflow
NCS weighted carbon
The following steps/rules are considered to create the NCS weighted carbon layer(s):
- Carbon layers:
- When multiple Carbon layers are provided, the average is calculated from the layers to create a single Carbon layer
- The produced Carbon layer is multiplied by the Carbon coefficient provided by the user in the settings
- If the Carbon coefficient is zero, the value is ignored
- NCS pathways:
- Multiply the pathway raster with the Suitability index
- If the index is zero, the pathway raster is used as-is
- Equation 1 shows how the NCS weighted carbon layer is calculated
Equation 1: NCS weighted carbon
where CarbonCoefficient is the carbon coefficient value multiplied with the averaged carbon raster;
Carbon is a carbon raster;
SuitabilityIndex is the NCS pathway index value;
NcsPathway is the NCS pathway raster; and
n is the number of carbon rasters.
- The results from the above calculation are normalized to create the normalized NCS Weighted Carbon layer
- A normalized raster's pixel values range from 0 to 1
- Normalization is done as shown in Equation 2
Equation 2: Normalized NCS weighted carbon
where value is the pixel value;
min is the minimum value of the raster; and
max is the maximum value of the raster.
Activity
- Because an activity can consist of multiple pathways, the normalized results will be summed
- All NCS weighted carbon layers, as created from Equation 2, are summed as shown in Equation 3 to create the activity from the pathways
Equation 3: Summed pathways for the activity
where NcsWeightedCarbon is a pathway set up by the user; and
n is the number of pathways.
- Now that the pathways have been summed for the activity, the result needs to be normalized
- The Suitability index and the Carbon coefficient then needs to be taken into account after the normalized raster has been created
- This calculation is shown in Equation 4
Equation 4: Final activity created from pathways
where value is the pixel value;
min is the minimum value of the raster;
max is the maximum value of the raster;
SuitabilityIndex is the NCS pathway index value; and
CarbonCoefficient is the carbon coefficient value multiplied with the averaged carbon raster.
- The resulting output is the final activity
Priority weighted layer (Weighted activity)
- This step is performed after the activities have been created
- The PWL is more important, and will therefore be multiplied by five to take this into account
- The PWL weighted is calculated as shown in Equation 5
Equation 5: Priority weighted layer (Weighted activity) calculation
- The resulting PWL will then be used as input to the Highest position calculation
Highest Position
The Highest position tool determines the raster in a stack with the highest value at a given pixel. Essentially the result is a classification, where each class represents a specific activity. If multiple rasters has the highest pixel value at a given pixel, the first raster with that pixel value in the stack will be used. Figure 2 shows an example from the QGIS description of the Highest position tool.
Figure 2: Highest position example
In the plugin, the nodata values are ignored. This means that if at least one raster has a pixel value at that cell there will be a raster stack value. If none of the rasters in the stack has a pixel value at that cell (e.g. each raster pixel is nodata) the output will be nodata at that pixel.
Here is an explanation of how to use the Highest position tool:
- Figure 3 shows the layer for the Highest position at stack position 1
Figure 3: Layer 1 used as the highest position input
- Figure 4 shows the layer for the Highest position at stack position 2
Figure 4: Layer 2 used as the highest position input
- Figure 5 shows the result from the Highest position calculation (Scenario result)
- Stack layer 1 (blue): Figure 2 raster had the highest pixel value
- Stack layer 2 (red): Figure 3 raster had the highest pixel value
Figure 5: Highest position result
This concludes the section on how the calculations are done
References
- https://www.pnas.org/doi/10.1073/pnas.1710465114
- https://royalsocietypublishing.org/doi/10.1098/rstb.2019.0126
Plugin
Detailed descriptions for each UI element of the plugin. This covers steps 1 to 3, dialogs, and the settings UI.
Dock widget
This is the main UI of the plugin. The dock widget opens on the right side of QGIS. The dock widget consists of three tabs, each focussing on a particular phase of the analysis. Here is a short description of those steps:
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Step 1: Scenario information. Click here for a detailed explanation.
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Step 2: NCS pathways and activities. Click here for a detailed explanation.
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Step 3: Weighting priorities (weighted activities). Click here for a detailed explanation.
For a detailed explanation of the plugin settings, the user can to refer the setting documentation