ArcGIS Tutorial: 3D polyline Features

　　What are 3D polyline (polyline) features?

A polygon feature is a GIS object whose geographic representation (a series of x-and y-coordinate pairs) is stored in a row of the database as one of its properties (or fields). Some line features, such as metro lines, also need to contain z-values or heights to correctly position themselves in 3D space. These objects must be modeled as 3D line features.

3D line features embed their z-values in the Geometry or Shape fields of their feature classes. This means that each new vertex created for a 3D line will automatically contain z-values, allowing it to connect any two points together-whether they are on the ground, above the ground, or below the ground.

Examples of 3D line features include:

Subway transportation;

Aircraft flight routes;

The sight between the buildings;

A transport network in skyscrapers;

Although you can also model Z-values using the numeric feature attributes, this option displays all features with the same z-value in the entire line and may not support all the same analysis and interaction options supported by embedded Z-values.

All features that are located only on the elevation surface, such as streets, paths, and fence lines, should always be modeled as 2D line features. This simplifies the data storage and maintenance operations of the features and enables the features to automatically adjust the height when the underlying surface data is improved. In addition, if these lines require Z-values, you can use tools such as interpolation shape to calculate the Z-values of features by referencing the elevation data.

　　Two ways to create a 3D polyline (polyline) Feature class

There are two main ways to create a 3D line feature class: Create a new Line feature class or convert existing 2D line data to a new feature class that contains Z-values.

To create a new 3D line feature class: Select the coordinates include Z-values check box when defining the geometry of the feature class.

To convert existing 2D data, there are several options for setting the Z-value source, including: set to get the height value from the elevation surface or use an existing feature attribute.

　　What should the z-value indicate?

Z-values are primarily used to include elevations in GIS features. These values can represent absolute heights (such as the aircraft at 30,000 feet) or height relative to the ground (for example, a subway station located 50 metres below the ground). Both methods are fully supported when displaying and analyzing a generated 3D feature class.

It is important to note that Z-values can also be used to include other vertical measurements, such as air pollution observations, temperatures, and other measurements for surface generation. Creatively applying Z-values and what they represent are useful for understanding and analyzing data.

The units and planes of the feature class Z-values should be defined in the feature dataset where the feature class resides, if it exists, or in the feature class itself (if there is no feature dataset). If no units are defined, ArcGIS assumes that the units of Z are consistent with the units of XY. This assumption can be problematic, especially if the XY unit is a geographic unit (latitude/longitude).

　　Creating 3D polyline Features

You can create 3D features interactively in the geoprocessing framework using standard ArcGIS editing frameworks in ArcMap, ArcGlobe, and ArcScene, or with tools that include Z-values in the output.

ArcGIS Tutorial: 3D polyline Features