Workshop 3: Integrated Decision Units for Land Use Suitability Modeling#

Instructor: Dr. Changjie Chen ( Date: April 11 - April 15, 2022

Goal and Objectives#

The third GALUP workshop focuses on the creation of Integrated Decision Units (IDUs) using geoprocessing tools in QGIS. IDUs are land units, within which land properties (or attributes) are homogeneous. Such homogeneity ensures the integrity of a land use decision. For rural or less developed area, delineation of land units is a critical step that must take place before the process of land suitability analysis. Participants will be able to independently create IDUs for any region if base input data are provided. Specific objectives of this workshop include:

  • Understand key concepts of IDU and why it is useful to land use planning

  • Capable of using 16 tools in QGIS involved in the process

  • Independently create IDUs for different regions

An Integral Part of Land-Use Planning#

In 1976, the Food and Agriculture Organization (FAO) of the United Nations published A Framework for Land Evaluation, in which a system of philosophy and principles on the evaluation of land potential was developed. The framework was tested and adopted in many countries. In 1990, FAO published another report, Land Evaluation for Development, reiterated the significance of reliable land evaluation in the context of land-use planning and rural development, i.e., developing a rural area into an area of higher intensity of human activities, i.e., urban area. In this newer report, land evaluation and its relationship to (i.e., being a part of) the overall land-use planning process was further elaborated. As shown in the figure below, land evaluation is a procedure between Stage 2 and Stage 6, as well as a part of the Stage 7.

Fig 1. The process of land-use planning. Source: FAO. (1990).

The Stage 4, in parallel with identifying land uses (Stage 3), is identifying land units, e.g., IDUs.

Key Concepts#

  • Land unit: areas of land with specific characteristics (or qualities). For a comprehensive introduction of land unit, please check Zonneveld's paper.

  • Land characteristic: simple attribute that can be measured or estimated. For example, mean annual rainfall.

  • Land quality: a complex attribute that usually reflects the interaction of many land characteristics, such as susceptibility to flooding.

Implication of IDU#

Although any parcel of land can be considered a land unit, it is more efficient and meaningful to use parcels that can be adequately described in terms of one or a combination of land properties. A land unit should therefore represent an area that is, in terms of predetermined properties (such as floodplain, land cover, climate, soil), different from the surrounding land and can be assumed to have homogeneous land properties.

IDUs essentially are a set of polygons with definite boundaries. A specific land use can be assigned for each IDU based on land-use suitability analysis. Such assignment is referred to as a land-use decision. Due to homogeneity, the integrity of land-use decisions is assured. Since land-use decisions are intrinsically discrete (two adjacent parcels can have different uses, for example), a vector (polygon) representation is more applicable than a raster representation. That’s why we need to have a system of polygons, such as IDUs, to begin the land evaluation process. This is the first, however, critical step to develop a spatially explicit land-use plan.


Assignment Submission and Help#

The participants will have to sign into their GitHub accounts to submit assignments. Below is a video explaining how to submit the module assignments and how to request help through GitHub. Note: It may be convenient to open videos in the workshop in a new tab or window to easily navigate the GitHub page.


  1. FAO. (1976). A framework for land evaluation (No. 32; Soils Bulletins). Food and Agriculture Organization of the United Nations.

  2. FAO. (1990). Land evaluation for development. Food and Agriculture Organization of the United Nations.

  3. Zonneveld, I. S. (1989). The land unit—A fundamental concept in landscape ecology, and its applications. Landscape Ecology, 3(2), 67–86.