Raster data is a rectangular matrix of cells, represented in rows and columns. Real-world features and surfaces can be represented as vector data stored in a GIS. Vector data is defined by points, lines, and polygons and their associated relationships that comprise geospatial data. GIS data can generally be categorized into two major types: raster and vector. Points show where the concentration was sampled. The illustration below shows a surface model of chemical concentration across an area. A surface model approximates a surface by taking a sample of the values at different points on the surface and interpolating the values between these points. Because a surface contains an infinite number of points, it is impossible to measure and record the z-value at every point. Surface models allow you to store surface information in a GIS. Any of these values may be represented on the z-axis in a three-dimensional x,y,z coordinate system, so they are often called z-values. For example, points in an area on the earth's surface may vary in elevation, proximity to a feature, or concentration of a particular chemical. A functional surface is a continuous field of values that may vary over an infinite number of points. Raster, TIN, terrain, and LAS datasets are all types of a functional surface. You can also convert between these surface models. You can build triangulated surfaces by creating a TIN, terrain dataset, or LAS dataset. There are several interpolation methods to create raster surfaces, such as Inverse Distance Weighted, Spline, Kriging, and Natural Neighbor. The two main methods of creating surface models are interpolation and triangulation. These surface models can be created from a variety of data sources. ArcGIS can create and store four types of surface models: raster, triangulated irregular network (TIN), terrain datasets, and LAS datasets. Imaginary examples of 3D surfaces are often the types found in video games or computer simulation environments.Р”Р„ 3D surface is usually derived, or calculated, using specially designed algorithms that sample point, line, or polygon data and convert it into a digital 3D surface. Those contaminants could be mapped as a 3D surface too. An example of a derived surface is the contaminant levels of a particular bacteria in each well. These are all examples of real features, but surfaces could be derived or imaginary. Some simple examples of 3D surfaces are a landscape, an urban corridor, gas deposits under the earth, and a network of well depths to determine water table depth. A 3D surface model is a digital representation of features, either real or hypothetical, in three-dimensional space.

Panda3d reading digital terrain model