Overview of the functions of GIS

The core issues of geographic information system can be summarized into five aspects: location, conditions, trends, patterns and models.

1) Locations (Locations)

That’s what’s in a particular place.

First of all, the specific location of an object or area information must be defined, and the common definition methods are: determining the location through various interactive means, or directly entering a coordinate; second, after specifying the location of the target or area, you can obtain the expected results and all or some of its characteristics, such as the current parcel owner, address, land use, valuation, and so on.

2) Conditions

That is, where there is something that meets certain conditions.

First, you can specify a set of conditions, such as selecting from predefined options; filling in logical expressions; and interactively filling in forms on terminals.

Secondly, after specifying the conditions, you can get a list of all the objects that meet the specified conditions, such as showing all the features that meet the specified conditions on the screen with high brightness, such as the land type in which it is located, the valuation is less than $200,000, four bedrooms and a wooden house.

3) Trends

Such problems need to integrate existing data in order to identify geographical phenomena that have occurred or are changing.

First of all, to determine trends, of course, the determination of trends does not guarantee that each time is correct, once a specific data set is mastered, the determination of trends may depend on hypothetical conditions, personal speculation, observation phenomena or evidence reports.

Secondly, in view of this trend, we can confirm or negate it by analyzing the data. Geographic information systems allow users to quickly obtain quantitative data and charts illustrating the trend. For example, through GIS, the characteristics of this trend can be identified: how many citrus plots have been converted to other uses? What’s the use now? How many such changes have taken place in a region? How many years can this change be traced back? Which time period best reflects this trend? One year, five years or ten years? Has the rate of change increased or decreased?

4) Patterns

Such problems are related to the analysis of events that have occurred or are occurring. Geographic Information System (GIS) combines existing data to better explain what is happening and find out which data is relevant to what happened.

Firstly, the determination of patterns usually requires long-term observation, familiarity with existing data and understanding of the potential relationship between data.

Secondly, after the mode is determined, a report can be obtained showing when and where the event occurred and a series of maps showing the event. For example, motor vehicle accidents often conform to a specific pattern, where does the pattern (accident) occur? Does the place of occurrence have anything to do with the time? Is it at a particular intersection? What are the conditions at these intersections?

5) Models

The solution of this kind of problem needs to establish a new data relationship to produce a solution.

Firstly, models are established, such as selection criteria, testing methods, etc.

Secondly, after establishing one or more models,which can generate a list that satisfies all the specific features, emphasizing the map of the selected features, and providing a detailed description of the selected features. For example, to build a children’s bookstore, the evaluation indicators for site selection may include 10, 15, 20 minutes of reachable space. The number of children aged 10 or under living nearby, the income of nearby families and potential competition around them.

In order to accomplish the core tasks of the above-mentioned geographic information system, different functions need to be used to achieve them. Although the advantages and disadvantages of current commercial GIS packages are different, and the technologies they use to implement these functions are also different. However, most commercial GIS software packages provide the following functions: data acquisition (Data Acquisition), preliminary data processing (Preliminary data Processing), data storage and retrieval (Storage and Retrieval), data query and analysis (Search and Analysis), graphic display and interaction (Display and Interaction).

Figure 1-8 illustrates the relationship between these functions and the different representations of their Manipulation data.

As can be seen from figure 1-8, data acquisition is obtained from real-world observations, as well as from existing files and maps. Some data are already in digital form, but data preprocessing is often needed to convert the original data into structured data so that it can be queried and analyzed by the system. Query analysis is to obtain a subset of data or transform it, and interact with real results. In the whole processing process, we need the support of data storage and retrieval and interactive performance, in other words, these two functions run through the GIS data processing all the time.

** Six components of spatial information processing and analysis [Ding Yuemin]**

1. Spatial operations, such as map union, intersection, subtraction, buffer calculation, selection, etc.

2. Spatial statistical analysis is used to describe and analyze the relationship between spatial data, such as spatial autocorrelation analysis.

3. Spatial model, focusing on spatial phenomena, spatial structure, spatial relations and spatial location analysis, such as network analysis and water system generation, etc.

4. Spatial representation/visualization, focusing on the expression of spatial information;

5. Spatial database management, including spatial database design, spatial data structure, spatial data management and spatial query.

6. Spatial model base management, including model management for spatial decision support system, etc.