The Draw Land Use command is used to manually define land use on the Map View by interactively painting in the areas of land use. The painted areas are automatically converted into polygons with attribute data associated to the assigned land use. The defined land use polygons are then used to compute the composite hydrologic parameters for each catchment area.
Note that the user does not have to “paint-in” land use for the entire watershed being analyzed. The user can select a “default” land use which is then applied to areas that do not have a land use defined.
From the Input ribbon menu, select the Draw Land Use command. Selecting this command will display the following panel floating to the right side of the Map View.
When selecting this command, if the Map View is in 3D view mode (even if viewing from directly above), the software will force the Map View into 2D view mode. This is because this command needs the user to define areas of land use, and the Map View must be in 2D mode to perform this task.
Note that prior to using this command, the user needs to assign a CRS to the project. Refer to this article in our knowledge base to learn about how to assign a coordinate reference system to a project.
The various subsections of the Draw Land Use panel are discussed below.
The General Specifications section of the Draw Land Use panel is used to define the following properties:
- Land use layer
This entry is used to define the land use layer to add to the land use polygon data.
Clicking on the pencil icon will allow the user to rename the selected land use layer.
In addition, at the top of the listing is an Add New Layer entry, which will create a new layer.
- Land use layer transparency
This option adjusts the transparency of the land use being painted using the horizontal slider, allowing the user to see through the defined land use areas to the underlying displayed map. Default transparency value is 50%.
Map Definition Tools
The Map Definition Tools section of the Draw Land Use panel is used to define land use polygon areas and perform various operations on the same. The software provides two modes: overwrite mode and clip mode, which are used to draw straight and curvilinear polylines, trace existing polylines, paint the land use areas, and fill polygons. In addition, the software also provides various tools to edit the drawn land use areas.
The two modes are as follows:
- Overwrite mode – Overwrites any existing overlapping land use areas
- Clip mode – Clips the current land use painting to existing overlapping land use areas
The different tools provided in the Map Definition Tools section are as follows:
The following observations apply to the Draw tool:
- While drawing land use, the start and end points take the shape of the selected nib, as shown below.
- When starting to draw land use by holding down the [Shift] key, the drawing is done along a straight line. Similarly, if the user holds down the [Ctrl] key while drawing, the drawing is done along a curvilinear line.
The following observations apply to the Fill Area tool:
- Filling will only occur if the selected location is surrounded by other land use polygons. It will not work in areas that are not surrounded.
- Filling in an area will cause the currently selected land use to fill into the empty void space.
- Adjacent land use areas of the same type will merge with the filled-in land use area.
The following observation apply to the Erase Tool:
Creation of interior holes (doughnuts) is supported when erasing land use areas. For example, the user may erase the park area that is surrounded on all sides by a street land use.
Delete Land Use Polygon
Clear All Land Use
The Nib Style section of the Draw Land Use panel is used to choose a nib style (circle, square, or diamond) and/or adjust the nib size. (A nib is the part of a quill, dip pen, or fountain pen which comes into contact with the writing surface in order to deposit ink.)
The nib size is defined in pixels, and the paint tool and erase tool will change in size according to the selected nib size.
Land Use Palette
The Land Use Palette section of the Draw Land Use panel is used to define various land uses and their associated properties, as well as allow the user to easily switch between various land uses while painting the land use areas onto the Map View.
The following features are provided in the land use palette section.
- The […] lookup button is used to select the land use with associated curve numbers and impervious values. Clicking on this button will display a Select Land Use lookup table dialog box.
- The Impervious (%) column displays the imperviousness associated with a specific land use or land type.
The following button commands are listed at the bottom of the land use palette.
- To define various land uses and their associated properties
- To style the border associated with the land use polygon(s)
- To change the image’s transparency
- To change the current CRS (coordinate reference system) of the project, etc.
Refer to this article in our knowledge base to learn more about the Land Use Properties dialog box.