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Raster images or surface are more designed for analytical purposes. A raster image constitutes of over thousand of cell each containing values that can be analyzed or used in algorithms. Triangular Irregular Networks or TIN's are more used for surface display purposes. TIN's are vector based representations of the physical land surface made up of irregular distributed nodes and line with 3D coordinates (x,y and Z) that are arranged in a network of non-overlapping triangles.
TIN's can basically be created from various data formats such as contour lines, sample points, raster images, any data containing coordinates (x,y) and the most important 3D values (z) which in most cases are depth or height values.

I will derive data contained in this raster to create a 3D TIN model of the project

Cells Constructing a Raster

A large raster surfaces are constructed by combining these tiny square cells together. Each cell is registered in a database with their values or attributes. Attributes such as x,y coordinates and z values extracted from the cells will be sufficient enough to create a TIN for my modelling purposes.

Contructed TIN

The algorithm used in creating TIN's are complexed but pretty easy to master. The most important data in this stage are the x,y coordinates and the z values. The TIN is presented in a uniform color and requires further processing before an accurate representation of the entities can be achieved.

Triangles Constructing a TIN

Its clear in this image that the cells were replace by "triangles". Its important to know that the "triangles' does not constitute any data or attributes.

TIN with Contours

I created this TIN purely from collecting sample points from a contour map and manipulating the points in the geodatabase.

Contours with Attribute Table

Vector Vegetation Layer

Data in this vegetation layer is in vector form and not triangulated. To add this layer to the TIN a process of re-triangulation is done. The boundaries of each polygon is "traced" onto the TIN creating a boundary. Re-triangulation then occurs within these new boundaries creating much smaller and unique triangles.

Tagging Vegetation

As noted with a close up view the red boundaries "traced" around the vegetation polygons onto the TIN. This process is called "tagging".

Vegetation Triangulated

After the tagging process is done the entire TIN surface is once again re-triangulated. Triangles don't cross any boundaries setup in the algorithm thus the re-triangulated process creates various new surfaces which representation both vegetation and landformations.