SuperMap SDX + Spatial Data Model

Data model is an abstract description of the real world. Using these models, we can model the real world into the computer, and perform operations such as display, query, editing and analysis.

Four integrations of data model

Integration of Raster Data and Vector Data
Because Of the difference in data structure between Raster Data and Vector Data, Vector Data and Raster Data are often stored, managed and displayed separately in most GIS software, while SuperMap GIS adopts compound document technology and database technology. Raster Data and Vector Data are stored in the same Datasource to realize the integrated management, display and analysis of Vector Data and Raster Data.
Object-oriented and topology-oriented integration The
Early GIS software used the data structure of "node-arc-face" (topology-oriented) to store Spatial Data, and with the development of object-oriented concept, GIS software began to tend to use object-oriented data structure to store Spatial Data. But then the Topology between spatial objects is missing. SuperMap SDX + initiatively stores the object-oriented point, line, surface and Text model and the topology-oriented Network Data model in the same Datasource, and provides the mutual transformation between them, so as to select according to the actual application.
Integration of GIS and CAD
Traditional GIS generally uses Layer Style and thematic map to set the display style of the map, and each layer of data is a single Object Type, such as line layer only has line objects, surface layer only has surface objects, etc. Parametric spatial objects such as arc and Rounded Rectangle are not provided. For the convenience of engineering drawing, CAD software uses a large number of parametric Geometry, and different types of objects can be stored in one layer. The traditional GIS method is convenient for Spatial Analysis and calculation, while the CAD method is more conducive to mapping expression and reducing storage space, and improving the drawing accuracy of large-scale features. SuperMap SDX + combines the advantages of both. In the same Datasource, it can not only store a single type of object through point, line, surface, text and other data models, but also store multiple types of Geometry (including parametric objects) through composite data models, and each object can have its own display style. The Composite data model of SuperMap SDX + can directly access CAD data including DXF/DWG of AutoCAD and DGN of MicroStation, preserve the attributes and styles of the original data, and easily add CustomProperty. It perfectly realizes the replacement from CAD software to modern GIS software.

In SuperMap SDX +, the concept of Compound (GeoCompound) is also proposed, which can aggregate various types of Geometry, and can also aggregate other compounds, so that any complex object can be drawn and managed. It also supports Block in AutoCAD and Cell in MicroStation.
Integration of different storage media
Early GIS software generally uses files to store Spatial Data. With the development of database technology, more and more applications use Spatial Data database in medium and large GIS engineering applications. In recent years, the development of server and the emergence of SOA. OGC standard network services (WFS, WMS, WCS, TMS and WMTS) are also increasingly used. SuperMap SDX + allows you to manage and edit the data from different sources (File Database, Datasource, and WebDatasource). In a SuperMap map, data from different Datasources can exist at the same time. And can be saved collectively in Workspace.

Application example of model selection

When we simulate the real world, we will choose different data models to describe according to the different research backgrounds. For example, rivers, we know that rivers are important elements in human society and nature, human beings can use rivers for transportation or as administrative boundaries, and animals in nature often use rivers as habitats or habitat boundaries. In GIS, there are different modeling methods for rivers for different application scenarios, as follows:

In the study of urban water network, rivers, as the line elements of urban water network, need to be described by Network Data model. Each line has the attributes of length, flow direction, capacity and so on. In real life, you can use Facility Network Analysis in Network Analysis to find the source of a river, find the Common Upstream or Common Downstream of several tributaries, and trace tributaries such as pollution sources from polluted waters.
When the analysis only focuses on the length and flow direction of the river without considering the area and width of the river, the river can be described by the line data model. For example, when the Yellow River passes through Shaanxi and Shanxi, it serves as the administrative boundary, as shown in the figure.
In large scale, rivers are generally expressed by surface data model, which has Attributes such as width, depth and load. For example, if we want to study the bridge on the river, we must consider the width of the river, and if we want to study the island in the middle of the river, we must consider the area of the river.

The example of a river shows that a simple element like a river has a variety of data models to describe. Therefore, when describing the real world abstractly, the best general data model does not exist. The choice of a data model should depend on the specific application scenario and what problems need to be solved. For different problems, different models are selected to simulate the real world.

Data Model type

Point data model

Point data model (Point): a point is a zero-dimensional shape that is stored as a single X, y coordinate pair with attribute values. Used to represent geographic features that are small at a certain scale but cannot be described as line or surface objects.

Any object has its size and shape. The point data model mainly expresses the spatial Position Info of the object, and does not care about its shape, size, etc. For example, if we only want to know the location of the Himalayas, the Himalayas will be described by the point data model on the World Map. In SuperMap GIS, different symbols are provided to express points with different meanings.

Line data model

Line data model (line): a line is a one-dimensional shape stored as a series of ordered X, y coordinate pairs with attribute values. The wire data model allows for wired complex objects. The shape of the line can be a straight line, a polyline, a circle, an ellipse, or a rotary line, wherein the circle, the ellipse, the arc, and the like are converted into the polyline for storage. The line data model is used to represent linear geographic features that cannot be described as surfaces at a certain scale. When we only pay attention to the direction, length and other one-dimensional information of these geographical elements without considering their width and area, they can be described by line data model, such as rivers as provincial boundaries, small-scale urban roads and so on.

The difference between a simple Geometry and a complex Geometry: a simple Geometry is generally a single object, while a complex object is composed of multiple simple objects or generated after certain spatial operations. For example, when drawing the basin of the Yellow River, there are many simple line segments representing the main stream and tributaries. When the main stream and tributaries of the Yellow River need to be viewed as a whole, these tributaries and main streams need to be combined into a complex line object to represent the whole basin of the Yellow River.

Face data model

Face data model (Region): a face is a two-dimensional shape stored as a series of ordered X, y coordinate pairs with attribute values. The X, y coordinates of the last point must be the same as the X, y coordinates of the first point. It is used to describe a closed geographical element with a certain area surrounded by a series of line segments. For example, the province in the administrative map will be represented by the surface data model, or the river in the large scale will also be represented by the surface data model.

The facet data model has facet complex objects, which is very necessary when describing geographical elements. For example, the whole city of Shanghai is composed of four facets of Shanghai downtown, Chongming Island, Changxing Island and Hengsha Island. Because these four facets are a whole, we cannot use simple objects to describe correctly, but need to use complex facets.

Pure attribute data model

Tabular Dataset (Tabular): a Tabular Dataset is a collection that stores and manages pure attribute data. The Tabular Dataset has no spatial graphic data, that is, the Tabular Dataset cannot be displayed as a layer in the Add to Map window. Pure attribute data can be used to describe terrain features, shapes and other information, such as the length and width of the river. Some social and economic data and Statistical Data can also be used as pure Attributes.

Text model

Text (TEXT): stored in two parts, the first part is the X, y coordinate pair with the attribute value (called the anchor point of the text, and the upper left corner of the minimum Bounds of the text); The second part is Text Property, including content, font, font size, font height, bold font, Rotation angle, Font Color, Background Transparency, Fixed Size, etc., as shown in the following figure.

Background Transparency and Fixed Size for Text. Background Transparency: Select the Background Transparency of the text (the text to be added). Otherwise, the background color of the Show Settings is Background Transparency by default; Fixed Size: that is, the size of the text does not scale with the scaling of the layer. If the text represents Map Information and needs to scale with the scaling of the map, the Fixed Size is not required. If the text only represents information unrelated to the scale, such as place names, the Fixed Size is required. When Fixed Size is set, the Font Height of the text cannot exceed 255 logical units (0.1mm here). If it exceeds 255, the system automatically sets its Fixed Size to 255.

In most cases, the text is used as a map annotation or auxiliary description. When annotating a map, you can use a text layer composed of Text directly or use a Thematic Label Map.

Label content in Thematic Label Map can be constructed by field expression, and can represent labels in various forms, such as score form, combination of multiple field contents, etc., and can also set properties such as No Overlap and Flow. The Text Styles in a Thematic Label Map layer are unified. Each Text on the Text Dataset can be set to an independent display style.

In general, using Thematic Label Map for annotation is more flexible and easy to adjust. When you need to fix the position, have a separate display style, or export as a Data Import, you can choose to use Text Dataset. SuperMap GIS provides the function of saving Thematic Label Map "as Text Dataset". You can make a Thematic Label Map first, then save it as Text Dataset, and finally adjust the specific text according to your needs.

CAD (Composite) Data Model

CAD (Composite) Data Model: Refers to a data model that can store multiple types of Geometry, as shown in the following figure. CAD data has the characteristics of beautiful graphics and small storage space. At the same time, CAD software (such as AutoCAD, MicroStation, etc.) Is mostly used in the early GIS engineering applications, so in the early development of GIS, CAD data contributes a lot to the digitization of maps, but CAD data is not easy to extend attributes and lacks GIS analysis functions.

With the development of GIS Application, it is necessary to transit from CAD software to GIS software. This requires that CAD Data can be imported into GIS software, and even requires that GIS software can directly read and edit CAD data. SuperMap GIS introduces a composite data model, which specializes in storing and managing data similar to CAD data structure or Spatial Data similar to CAD usage. CAD data including DXF/DWG of AutoCAD and DGN of MicroStation can be directly accessed through the composite data model of SuperMap GIS, and the attributes and styles of the original data can be saved, and CustomProperty can be easily added.

Data formats supported by the CAD data model:

CAD can store different types of Geometry such as point, line, surface and text, as well as different types of Parametric objects . All objects can have their own style.

CAD data models differ from simple data models (point, line, and area data models) as follows:

CAD data model can store multiple types of data, such as point, line, surface, text, etc., while Simple Dataset can only store one type of data. For example, only points but not lines or surfaces can be stored in the point data model.
Different styles can be set for different objects in CAD Dataset; however, all objects in Simple Dataset have the same style, and different styles need to be set through Layer StyleUniform Settings or thematic map according to Attributes.
Several objects in a CAD Dataset can be combined to produce a Compound. After combination, the attribute record of Compound is added to the end of the attribute table. System Field: Assigned by the system. Non-system Field: Retains the corresponding attribute value of the object with the smallest SMID value in the combined object. The source object and the corresponding attribute record are deleted. Compound can be combined with other compounds or simple objects to generate a new Compound. For example, when we draw landscape planning and design drawings, we need to use many symbols, which are composed of points, lines, surfaces and texts. At this time, we combine these points, lines, surfaces and texts to generate a complex object, which is convenient for drawing. For example, the disabled sign is represented by a round surface, an arc and several broken lines when we draw it. We combine it into a Compound, which can be moved and pasted as a whole in the future drawing, as shown in the following figure:
Ellipse and circle in CAD Dataset are stored by parameterization, for example, the X and y coordinates of the center of the circle and the length of the radius are stored; while Simple Dataset stores a series of X and y coordinate pairs of ordered points. This is shown in the following figure (parametric storage on the left and point coordinate pair storage on the right).

Route Data model

Transportation departments generally use linear reference systems to determine events (such as accidents and speed limits) and facilities (such as bridges and intersections) along transportation routes such as roads, rivers and pipelines. A linear frame of reference determines the location of an event with distance measurements from a known point, such as the start of a path, a milestone marker, or a road intersection. For example, the address of the accident location includes the road name and the distance from the milestone marker.

SuperMap GIS provides the Route Data model (Route) to describe the line under the linear reference system in the transportation sector, as shown in the figure below.

Route Data model (Route): It is stored as a series of ordered X, y coordinate pairs with attribute values and M values, where M value is the distance attribute of the node (the distance to a known point), as shown in the following figure. The Route Data model is actually a linear data model with an M value. The most common Route Data models, such as milestones on the highway, are often used by traffic control departments to mark and manage highway conditions, vehicle speed limits and high-speed accident points. Based on the Route Data model, the Dynamic Segmentation function can be used to locate dynamic events, that is, to locate point events (such as accident points, bridges, etc.) Or line events (such as speed limit sections, road conditions, etc.) According to specified conditions.

Network Data model

Network Data Model (Network): Used to store the data model with network Topology. The Network Data model includes the Network Line Dataset and the Network Node Point Dataset, and also includes the spatial Topology between the two objects. In a Network Dataset, a network node is stored as a child Dataset. The Network Data model and physical storage are shown in the following figure:

Based on the Network Data model, Path analysis, Service Area Analysis, Find Nearest Facility, Resource Allocation, Location-Allocation, and adjacency points can be performed. Access point analysis and other Network Analysis, mostly used for government and business decision-making.

Mosaic Dataset Model

Mosaic Dataset Model (Mosaic): Mosaic Dataset is used to manage data in raster format. Images in different formats (*.tif, *.tiff, *.img, *.ecw, *.pix, *.sid) can be added to the same Mosaic Dataset. Mosaic Dataset is managed by metadata + original Image Files. When adding Image Data to Mosaic Dataset, only the path, contour, resolution and other meta-information of Image Files will be recorded in Mosaic Dataset, and the required Image Files will be loaded according to the meta-information when using. Compared with the traditional warehousing management mode, this mode greatly improves the speed of warehousing and reduces the occupation of disks.

Video data model

Video data model: Video is one of the important information carriers for perceiving the dynamic changes of the environment. As a universal public media resource, video is not only a visual product, but also a kind of natural Geographic Spatial Info data because of its space, time, rich information, diverse content and true expression. SuperMap iDesktopX combines AR, AI, video and other technologies to provide video access, video spatialization, Video Map, Video Analysis and other functions.

Model Dataest

Model Dataest (Model): Model Dataest is a newly added Dataset mode, which converts the model into Dataset for storage instead of storing the model in CAD. This enables Model to be unified with other types of Dataset in terms of management and operation, while being more efficient and smooth in terms of display efficiency.

GRID data model

GRID data model: It is a kind of Raster Data model. It divides a plane space into rows and columns regularly to form a regular grid. Each grid is called a cell (or pixel). The Raster Data model is actually a matrix of cells. Generally, each cell has a definite value to represent a geographical entity or phenomenon, such as soil type, Land Use type, rock depth, etc. For cells with missing data, they are usually represented by NoData or a fixed special value, such as -9999. The following figure shows a Land Use type image:

Raster Data statistics, Algebraic Operation and other calculations based on mathematical analysis and graphic processing can be carried out based on GRID data model. The most widely used Raster Analysis is Spatial Analysis, which has obvious physical meaning. Such as the analysis of raster terrain surface, Hydrological Analysis based on terrain surface, the extraction of terrain feature lines, terrain surface modeling and other commonly used analysis and calculation in scientific research.

GRID data can be encoded before storage. At present, the main Encode Type is SGL (SuperMap GRID LZW), which is a lossless compression. SGL is an Encoding Format customized by SuperMap and an improved LZW (Lempel _ Zir _ Welch) Encode Type. This Encode Type can not only compress duplicate data, but also compress non-duplicate data. At present, SuperMap GIS uses the Encode Type of SGL for GRIDDataset and DEM Data sets.

Image Data model

Image Data Model (Image): It is a Raster Data model obtained by the imaging system on the satellite or aircraft. The value of each grid is the reflectivity of light in a certain band. According to the Image Data of the earth's surface, we can analyze the Land Use of the earth's surface, the growth of vegetation, the distribution of minerals, or the meteorological conditions according to the cloud pictures of the earth's atmosphere.

Images can be divided into single-band images and multi-band images according to the number of bands. Single-band images are generally described by black and white grayscale maps, while multi-band images are described by RGB composite color maps.

Image Data is generally large, and it is recommended to compress it first when SuperMap performs Data Import. SuperMap GIS image compression usually uses DCT (Discrete Cosine Transform) coding. DCT is discrete cosine coding, which is a transform coding method widely used in image compression. This method has high compression ratio and performance, but the coding is distorted. DCTEncode Type is recommended because Image Dataset is generally not used for precise analysis.

If it is a Image Data Create Image Pyramid, the data browsing speed can be greatly improved. Image Pyramid is a collection of a series of simplified resolution images in Raster Dataset. Through the Image Resampling Method, a series of Image Layers with different resolutions are established, each layer is divided and stored, and the corresponding Spatial Index mechanism is established. This improves the Display Speed when zooming through the image. As an example of the Image Pyramid shown in the figure, the Image Pyramid has four layers, that is, four levels of resolution. For an image with an image resolution of 2a × 2b (a > B), a pyramid of (b-6) + 1 layers will be established in SuperMap.

After the Image Pyramid is established for the image, the system will obtain its Image Pyramid to display the data every time you browse the image. When you enlarge or reduce the image, the system will automatically select the most appropriate pyramid level to display the image based on the user's Display Scale. And that display rate is greatly improve.

SuperMap GIS also provides a new Image Files Storage Format: SuperMap Image Tower, which integrates image compression and efficient Image Pyramid technology. It can not only compress Image Data by a large margin, It can read and display at a very fast speed, which solves the problem of slow Display Speed of super-large Image Data.

SuperMap SIT uses 64-bit encoding and can support very large files, theoretically up to 263 bytes in size (about 8000 TB). It can completely merge all Image Data in general applications into one file. In practical applications, it is only limited by the size of the hard disk partition and the file system of the partition.

The SuperMap SIT provides a password-protected feature that allows the SIT to be encrypted to protect the security of the data.

SuperMap SDX + provides a custom ImagePlugins engine that supports direct opening of BMP, JPG, TIF, SCI, RAW, and SIT. You can also customize the image format according to the header File Info provided by us and open it directly with SuperMap SDX +.