About Topology

GIS is to transform the paper maps into digitized maps and truly displays the spatial information that the maps convey. For instance, a map uses different symbols, colors and shapes to represent location name, road, school and administrative district.

To let computers understand the spatial relationships, users need to generate “Topology” for spatial information that can be applied to more advanced analysis and processing.. In practice, users need to define the data model and calculate the result of spatial relationships with related algorithms.

Through Topology, the location of spatial information and the spatial relationships of features can be well described. Furthermore, the results can be applied to query and analysis; also, the results are the essential references for decision-making.

Topology application

SuperGeo is going to release the new Topology Analyst, which provides cartographers with the most convenient tool to inspect the spatial relationship and do quick correction. In addition to the new manipulation design, the new analyst allows users to work with multiple layers at once. Meanwhile, some common topology rules are available to use and map can be corrected right after inspection; thus the partial spatial relationship can be effectively recreated. Topology analyst is definitely a crucial tool for cartographers, which enhances their working performance significantly.


The brand new Topology analyst

To correct the map with new Topology analyst, a Topology object must be created in SuperGIS Desktop map environment first. This Topology object is not a physical layer but more like an independent environment for inspecting and correcting map. When creating this environment, we need to decide some basic settings: 

A.Cluster Tolerance:

Tolerance must be considered when users are inspecting maps. It filters those line and polygon features which are too small or the vertices which are too close to each other; cartographers can decide to remove or keep the filtered ones.

B. Feature Classes:

Generally it refers to point, line and polygon layers of vector format. Because cartographers usually correct maps with multiple layers at once, the analyst allows users to add multiple Feature Class layers to the same Topology environment. As a result, these layers can be processed based on the same settings.

C. Topology Rules:

It represents the rules for inspecting spatial relationship between point, line and polygon. Topology analyst 1.0 only has Dangle Nodes and Pseudonodes rules: however, in version 3.0, there are more than 20 Topology rules for point, line and polygon types. Furthermore, multiple rules can be added to one Topology environment to help inspect whether the spatial data obey all the Topology rules.

D. Symbology:

The symbols assist cartographers in error correction. Cartography is a hard visualization task; in different Topology environments, users can set symbols to represent error point, line and polygon during inspection. Also, users can define the less important errors as exceptions and distinguish them in other symbols. Moreover, cartographers can review the inspected areas which have not been corrected. These areas can be displayed in so-called Dirty Area symbol.

When basic settings are finished, start to inspect and correct map. In SuperGIS Desktop environment users can decide to inspect the extent covering all Feature Classes or some specific area only by dragging a frame on the map to accomplish the inspection task effectively.

Inspection is performed based on the Topology Rules; the found errors or exceptions will be labeled with specific symbols on the map after inspection and then users can start to correct. Before starting correction, cartographers can read the description and understand the error type by using error review function so that they can know whether the results are indeed what they need. After confirmation, the analyst will list the available correction methods for cartographers to choose, and then system will correct automatically without any editing tool.

During the process of correcting map, cartographers can inspect the spatial relationship at any time to ensure the progress. Also cartographers can partially or entirely inspect it according to the size of Dirty Area. All of the map corrections can be saved in project file for further use.

The topological data can be used for spatial analysis, such as creating files for different categories, urban planning, land resource management etc. The latest version of Topology will be released at the first quarter of 2012. Any suggestions will be appreciated.

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