Use custom soil data
Objective: Learn how to load custom soil organic carbon data to compute the carbon change sub-indicator using Trends.Earth.
Estimated time of completion: 20 minutes
Internet access: Not required
Loading custom soil organic carbon data
This tool assumes that the units of the raster layer to be imported are Metrics Tons of organic carbon per hectare. If your layer is in different units, please make the necessary conversions before using it in Trends.Earth.
The Load data menu will open. Select Soil organic carbon from the Import a custom input dataset section.
In the Load a Custom Soil Organic Carbon (SOC) dataset use the radio button to select the format of the input file (raster or vector). For this tutorial select raster, since the data distributed by the UNCCD is in raster format. Click on Browse to navigate to the soil organic carbon file you wish to import.
Use the Select input file window to navigate to the file to be imported, select it, and click Open.
Back at the Load a Custom Soil Organic Carbon (SOC) dataset window you have options for selecting the band number in which the productivity data is stored, in case your input file is a multi band raster. You also have the option of modifying the resolution of the file. We recommend leaving those as defaults unless you have valid reasons for changing them.
Define the year of reference for the data. In this case, we will assume the soil organic carbon data is from 2000, but if using local data, make sure you are assigning the correct year.
Click Browse at the bottom of the window to select the Output raster file.
Navigate to the folder where you want to save the file. Assign it a name and click Save.
Back at the Load a Custom Soil Organic Carbon (SOC) dataset click OK for the tool to run.
A progress bar will appear showing the percentage of the task completed.
When the processing is completed, the imported soil organic carbon dataset will be loaded to QGIS.
Calculating soil organic carbon with custom data
Once you have imported a custom soil organic carbon dataset, it is possible to calculate soil organic carbon degradation from that data. To do so, first ensure the custom soil organic carbon data is loaded within QGIS (see Loading custom soil organic carbon data).
The “Calculate indicators” menu will open. Select “Soil organic carbon” from the “Option 2: Use customized data” section.
The “Calculate Soil Organic Carbon” window will open. Click the radio button next to “Custom land cover dataset” and select either “Import” to import a custom land cover dataset, or “Load existing” to load a land cover dataset you have already processed in Trends.Earth. Be sure to select both an “Initial layer” and a “Final layer”. See the Use custom land cover data tutorial for more information on loading land cover datasets. Once you have selected both datasets, click next:
On the next screen, click the check box next to “Custom initial soil organic carbon dataset”, and then use the “Import” or “Load existing” buttons to either import custom soil carbon layer (Loading custom soil organic carbon data) or to load an existing one that has already been calculated:
Click “Next”. Now, choose the area you wish to run calculations for:
Click “Next”. on the last screen, enter a task name or any notes you might wish to save (this is optional) and then click “Calculate”:
A progress bar will appear on your screen. Do not quit QGIS or turn off your computer until the calculation is complete.
Once the calculation is complete, three layers will load onto your map: 1) the final soil organic carbon layer, 2) the initial soil organic carbon layer, and 3) the soil organic carbon degradation layer:
For example, we can see areas of degradation in soil carbon around Kampala:
Refer to the Compute SDG indicator tutorial for instructions on how to use the imported soil organic carbon data to compute the final SDG 15.3.1 after integration with land cover and land productivity.