Create Isolines

Isolines are curves that unite surface points having same quota value.

Quota value meaning depends on surface physical magnitude intended to model. Thus to a surface that represents temperature it is obtained isothermal; to atmospheric forecast, isobaric; terrain height, level curves, etc.

Isolines can be viewed like being a plane projection (x,y) of intersections between the surface and an equidistant horizontal planes family.

The isovalue curves have some important properties among them: all are closed unless they intercept map definition border and never cross each other.

This plugin generates isoline or isovalue curves from the terrain numeric model in a rectangle and triangle grid format using a cell method.

It is accessible through: 

PROCESSING → DTM PROCESSING → CREATE ISOLINES... 

1. Select Input Layer

Use combobox or to select a layer that will be used to generate isolines. Be sure that there is a rectangle grid (raster) or a triangle grid (TIN) representation.

2. Set Step: 

• check Fixed: Isolines will be distributed equally in equal quote intervals. 

2.1. Insert  the quote Minimum value;
2.2. Insert the quote Maximum value;
2.3. Insert the  Step (interval value);
2.4. Click in to add values in the isolines quote list. The values ​​will be calculated according to the values ​​reported.

• check Variable:  The value of each quota must be informed. 

2.1. Insert the quote Value;
2.2. Click in to add value in the isolines quote list.

Repeat the the itens 2.1 and 2.2 until inserting all the quote values.

5. Create guidelines: when fixed step is selected, each line in five steps interval will be considered and created as a guideline. It will not be showed in a different style or width in the picture but indicated only in line attributes.

  to select output layer SRS.

7.1. to select the output directory and also inform the new layer name to store the result, or
7.2.  to select the Data Source and Inform the new Layer Name to store the aggregation result.