Calculation Method

The profile generator in Gemini Terrain has two different methods for calculating quick sections, longitudinal profiles, and cross-sections. You specify which method to use in the layer settings of the application layer. You can choose between the following methods:

• Calculate from original data
• Terrain grid

Different calculation methods: Left = Original data, Right = Terrain grid

Calculate from original data

The main principle of this method is that it only uses the elevation values from the original data. The method preserves exact intersection points in the profiles.

Advantages of this method:

• Finds data even where lines are missing
• Preserves sharp breaks in the terrain

Principle for calculation from original data: A = Intersection with source data, B = Interpolated points, C = Grid

How the method works is dependent on which method is selected for calculating the terrain grid:

• Contour lines
• Triangle network
• Point cloud

Triangle network

If the calculation method is Triangle network, the rule is simple: the method only uses the elevations from the triangle network's surfaces. Outside the triangle network, no data is generated.

Point cloud

If the calculation method is Point cloud, profiles are not generated directly from the points. The program performs the following operations:

1. Triangulates the points near the profiles
2. Generates profiles from these triangle networks

Triangulation of point cloud for profile generation

This way, you don't have to triangulate the entire point cloud in advance.

Note

The triangulation process occurs in the background, but you must specify the triangulation parameters in the profile generator.

Contour lines

With contour lines, the process is more complex. The line will typically not start and end exactly on original data points in the application layer. In these cases, the program generates the start and end points from the grid. Additionally, cross-sections must have a center point. If there are two exact intersection points within the width of the cross-section, the program interpolates between them. If not, points are generated from the grid.

Calculate from terrain grid

With this method, all points in the profile are generated directly from the terrain grid.

Info

You can adjust the grid density in Settings Gemini Terrain... - Project - General.

Advantages and disadvantages of this method:

• Finds data even where lines are missing
• Provides smoothing with lines "in the vicinity"
• Loses sharp breaks in the terrain

Principle for calculation from terrain grid: A = Intersection with source data, B = Interpolated points, C = Grid

Note

The size of the grid affects which sharp breaks are preserved in the profiles. A denser grid provides better reproduction of sharp terrain formations.