SDG 11.3.1 - Land Consumption Rate

  • Objective: Learn how to compute urban extent for 2000, 2005, 2010, 2015 in raster format and tabular outputs with areas estimated.
  • Estimated time of completion: 20 minutes
  • Internet access: Required

Compute urban area change

  1. Select the Calculate icon (iconCalculator) from the Trends.Earth plugin in QGIS.
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  1. The Calculate Indicators menu will open. In that window, click on Urban change and land consumption indicators (SDG indicator 11.3.1) button.
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  1. Select Step 1: Calculate urban change spatial layers
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  1. The Calculate Urban Area Change Metrics menu will open. In that window, you will step through the four tabs to set the parameters for your analysis.

Before you begin filling out these settings, you may wish to explore your area of interest using the interactive Urban Mapper page

Nota

Refer to the Urban Mapper section of this manual for a detailed explanation of how each of these sub-indicators is computed in Trends.Earth

  1. Settings
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By default your window will be open on the Settings tab. A. Select the Impervious Surface Index (ISI) by choosing a value between 0-100. The higher the value the smaller the urban area. B. Select the Night Time Lights Index (NTLI) by choosing a value between 0-100. The higher the value the smaller the urban area. C. Select the Water Frequency (WF) by choosing a value between 0-100. The higher the value the larger the urban area.

  1. Advanced
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Click Next from the Settings tab to view the Advanced tab. Here you will need to define the thresholds for suburban and urban built up areas. A. Define the area of largest captured open space (ha) which is the contiguous captured open space larger than this area that will be considered rural. B. Select which population density dataset you would like to use for the analysis.

  1. Area
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Click Next from the Advanced tab to view the Area tab. Here you will need to define the area for your analysis.

Nota

The provided boundaries are from Natural Earth, and are in the public domain. The boundaries and names used, and the designations used, in Trends.Earth do not imply official endorsement or acceptance by Conservation International Foundation, or by its partner organizations and contributors.

If using Trends.Earth for official purposes, it is recommended that users choose an official boundary provided by the designated office of their country.

You can select a country, region or city from the dropdown lists or upload an area from a file. If you select a city or upload a point location of a city, apply a buffer to the chosen area so that analysis encompasses all potential urban areas.

  1. Options
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Name the task and some note on how you customized the parameters for your analysis for future reference. When all the parameters have been defined, click «Calculate», and the task will be submitted to Google Earth Engine for computing. When the task is completed (processing time will vary depending on server usage, but for most countries it takes only a few minutes most of the time), you’ll receive an email notifying the successful completion.

  1. Download results
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When the Google Earth Engine task has completed and you received the email, click «Refresh List» and the status will show FINISHED.

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Click on the task and select «Download results» at the bottom of the window. A pop up window will open for you to select where to save the layer and to assign it a name.

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Then click «Save». The layer will be saved on your computer and automatically loaded into your current QGIS project.

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Compute urban area for 2000, 2005, 2010 and 2015

  1. Select the Calculate icon (iconCalculator) from the Trends.Earth plugin in QGIS.
../_images/ldmt_toolbar_highlight_calculate.png
  1. The Calculate Indicators menu will open. In that window, click on Urban change and land consumption indicators (SDG indicator 11.3.1) button.
../_images/calc_indicators.PNG
  1. Select Step 2: Calculate urban change summary table for city.
../_images/calc_urban2.PNG
  1. Input
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Load an existing .json file if it has not been populated within the dropdown automatically from your QGIS project.

  1. Output
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Select browse to navigate to a file on your computer and save the json file and excel table.

  1. Area
../_images/summary_area.PNG

Define the area for your analysis

  1. Options
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Enter a task name and notes for the analysis. This final step is calculated locally on your computer, it will load automatically in your QGIS project window.

8. View results A window will appear when the summary is complete. Select OK.

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  1. If an error window appears, select the Yes and the summary will proceed to open.
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  1. The summary table will appear and a spatial layer will be added to your QGIS project.
../_images/summary_table.PNG ../_images/urban_change.PNG

Urban Mapper

The Urban Mapper tool in GEE allows users to explore how changing different parameters impact the final output. Here we look at Kampala, Uganda:

../_images/calc_urban_mapper1.PNG

To get a better look at the fine details of the layers, we can zoom in to an area with the default parameters (ISI-20, NTLI-10, WF-25):

../_images/calc_urban_mapper2.PNG

Explore the changes to the map layers with changes to the Night-time lights parameter (ISI-20, NTLI-2, WF - 25)

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See how this changes with a higher Impervious Surface value (ISI-30, NTLI-2, WF-25)

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The area considered urban has decreased in size. Change the Impervious Surface to a lower number to see how it impacts the urban area (ISI-10, NTLI-2, WF-25)

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Zoom out to view the impact of these changes on the overall urban area in Kampala (ISI-10, NTLI-2, WF-25)

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In contrast, we can look at Dubai, an arid city.

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Adjusting the parameters we can see that Dubai would require a different set of parameters than Kampala (ISI-35, NTLI-5, WF-25)

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Change the Water frequency parameter to see the impact on the man-made islands of Dubai(ISI-35, NTLI-5, WF-80)

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