Generating a Rectangle Grid

The rectangle or regular grid is a digital model that shape surfaces through rectangle face polyhedron. Vertexes of those polyhedra can be the sampled points in case they have been acquired in same XY locations that define the wanted grid.

The rectangle grid generation must be done when a sampled data in the surface is not obtained with regular spacing. Thus from isoline contained information or in sampled points it is generated a grid that represent as closest as possible to the real surface. Initial values to be determined are x and y coordinate space in a way they can represent close values to the grid points in big variation regions. At same time, they should reduce redundancies in almost plane regions.

The grid space, i.e. x and y resolution, should be ideally lower or equal to the lower distance between two samples in different quotas. When generating a very thin grid (dense), with a very small distance between points, there will be a bigger amount of information about the analyzed surface, but will need more time to generate. Otherwise considering big distances among points, it will be created a thick grid that could lose information. Therefore, the final grid resolution must have a commitment of data accuracy and grid generation time.

Once defined the resolution and consequently the coordinate in each grid point, it is possible to apply one of interpolation methods to calculate the elevation rounded value.

The regular grid can be generated from samples, isolines, regular grid or irregular grid.

In the case of samples and isolines the following interpolators can be used:

 In order to generate a new regular grid from other regular grid the following interpolators can be used:
 For the generation of rectangular grid from a TIN ("Triangular Irregular Network") tthe following interpolators can be used:

It is accessible through:
PROCESSING → DTM PROCESSING → DTM GENERATION... 

1. Select the type of input layer. 

2. Use combobox or to select a isolines and/or samples layer. If you are not going to use both types of layer leave one blank, but one type should be selected.
If the selected layer does not have 3d information in its geometry, in the Quota Column combobox, select the attribute that contains the attribute to be used.
2. Use combobox or to select a grid retangular or triangular layer.
In the case of rectangular grid it is possible to set the dummy value of this.

3. Select the interpolator:

3.1. Set the Radius value: Maximum radius used to filter elements. Default value is calculated using box of input layer.
3.1. Set the Power : power value used in the IDW interpolator.
3.2. Inform the Radius : Maximum radius used to filter elements. Default value is calculated using input layer box.
3.1. Set Separation in X / Y: are the number of parts considered in the x and y directions.
3.2. Set Minimum Points: the minimum of points considered.
3.3. Set Overlapping: overlap value considered.
3.1. Set Tension: the tension spline factor considered in the spline fitting process.
3.2. Set Smothness: the smooth factor used.
3.3. Set Minimum Points: the minimum of points considered.
4. Inform Output Parameters
Resolution X / Y : grid space.
Dimension C / L : number of lines and columns.
Note that these values ​​are calculated as they are edited, when entering resolution the size of the grid is calculated and vice versa.

5. Set Output SRS
  to select output layer SRS.

6. Inform the Output Repository by clicking on:
6.1. to select the output directory and also inform the new layer name to store the result, or
6.2.  to select the Data Source and Inform the new Layer Name to store the aggregation result.

7. Click OK to perform the operation or Cancel to close the interface.