ArcGIS plotting skills (Part II)

2.4 graphic expression the graphic expression is used to represent data in a flexible and rule-based structure, which is stored together with the data in the geographical database. The element class supports multiple element class plotting expressions at the same time. Therefore, you can obtain multiple map products from a single database without storing data copies. Plotting expression of a single element (referred to as the element system)

2.4 graphic expression the graphic expression is used to represent data in a flexible and rule-based structure, which is stored together with the data in the geographical database. The element class supports multiple element class plotting expressions at the same time. Therefore, you can obtain multiple map products from a single database without storing data copies. Plotting expression of a single element (referred to as the element system)

2.4Graphic expression

A graphical expression is used to represent data in a flexible and rule-based structure, which is stored together with the data in a geographical database. The element class supports multiple element class plotting expressions at the same time. Therefore, you can obtain multiple map products from a single database without storing data copies. The graphic expression of a single element (referred to as the graphic expression of a factor) can be modified as necessary to permanently overwrite the graphic expression rule, which is also stored and maintained in the geographical database. While providing a rule-based Symbolic System's organizational structure, the graphic expression also retains great flexibility and allows you to customize the rendering methods of each element [1].

Therefore, the graphic expression inherits the rule-based matching mode of ArcGIS, and has the function of freely editing elements similar to the Common graphic software. Because the graphic expression is a series of attribute fields, rules and drawing methods are stored in the Attribute Table, the graphic expression can be separated from the geometric image, modifying the expression does not affect the data itself, so that modifications to the graphic expression during the drawing process do not cause any data risks.

You can use ArcGIS to plot several terms, elements, layers, and graphic expressions. It makes it easier to understand these three aspects.

An element is the most primitive data. It is a series of common dot and Line Graphics, without color or symbols. It is stored in files or databases. When data is loaded to ArcGIS, a layer is created by default. You can set the symbols and colors of these elements based on the layer. Layers actually associate our color scheme and symbolic scheme with data to achieve visualization. In general, the map can be drawn to the layer level. However, when there are higher requirements for advanced plotting or thematic plotting, it is necessary to use the graphic presentation. For example, in the National Topographic Map of (a map that can be published), there are clear rules on river painting. The source of the River must be fine, and the middle and lower reaches of the river must be rough according to the standard. In this case, we need to coordinate with the representation, which is the best choice.

There are also some higher requirements, such as line elements in the boundary part to the real reality of the intersection, the corner must be connected to the real, elements need vertical or horizontal distribution, these are not GIS Traditional Graphics can be processed, in this case, you can use the graphic expression to implement it.

The use of graphical expressions is generally to first use ArcMap to sign the data (the operation process of the 2.2 symbol system), and then directly convert the data to the graphic expression mode through the software. After being converted to a graphic expression, you can use its series of rules and special effects. As mentioned above, the thickness gradient of a linear River uses the cone surface effect of the line element in the graphic expression. You can view the graphic expression rules in the layer attributes, as shown in figure

In traffic and planning, some special effects may be needed to enhance the map display capability. For example, shadows are used at the intersection, and three-dimensional effects are used for buildings. The following graphic expression is used to create a three-dimensional effect for a two-dimensional building.

After converting it into a graphic expression, add the following offset effects. Click "+" on the top of the rule, add a "move" effect, and set the offset rules respectively, so that the layer will be offset. The offset-based plotting expression is dimmed to make it look like a shadow.

After that, you can add the original "building" to the map again (similar to creating a roadside line in 2.2, loading the same data twice in a row) and set it to a deep color. In this way, the whole three-dimensional effect will come out. As shown in

3 conclusion

Drawing is an art, but after being familiar with tools and skills, it becomes more technical and standardized. As a mature GIS platform, ArcGIS has outstanding performance in plotting. Reasonable Use of tools, appropriate time skills, and in-depth understanding of drawing rules are convenient for creating beautiful maps. With the continuous advancement of technology and people's understanding of maps, plotting will become easier and easier.