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Modeling Our World is about ESRI’s spatial database design and construction of libraries, of course, for other GIS platforms. Visited the original English version, this time bought a Chinese version of Posts and Telecom, translation also makes sense, color printing, the price is acceptable, binding style is not good, easy off page.
English is the Beta version of the original mark, it is not the content of some Chinese, but in fact lack of understanding of these elements have some impact. English version is also missing the grid, version, etc. section. Specific reason is unknown.
Books for most GIS practitioners have reference value, the core is to show how to abstract the real world objects to the appropriate spatial data models (vector, raster, …).
Summed up as a normal part of the original notes, comments and ideas for the blue part, chapters 1, 2, …
GIS as a platform or environment that can model the world, the core is to use digital maps to represent the real world. For a real space object, its model could be different, for example, is based on the discrete object model (vector), the continuous field model (grid or TIN), or a network, and its choice depends on the application of the final model purposes.
In other words, the model is the real world of abstraction, the so-called abstraction is a certain degree of simplification.
On the other hand, GIS base map leading to applications such as modeling received a lot of restrictions on the map itself. Such as scale, research, need to pay attention to its impact on the results, project development, you need a way to avoid its impact, such as multiple resolution maps for the different display (including the pyramid).
Geographical data model from CAD model to geographical data model (graphics and attributes stored separately), to the spatial database is a common technology and demand driven. ESRI’s spatial database is the object data model, ie, can be based on points, lines, and define their own object, the object has its own properties and rules, behavior.
Some people do it, or merely as an alternative to spatial database storage solutions. Individual has never been the case, because the degree of difficulty. Then to the review should not be users.
3 kinds of access ArcSDE ways: through ArcObject, fully object-oriented; by C, Java’s API, access to geographical data; through SQL, the raw data.
Map of how to present information.
Done on the definition of GIS, describes the application. Summarized as follows: First, GIS as part of the main applications embedded in other systems, whether research or application; second, the importance of opening up; third, print the map is not the main purpose; Fourth, the data structure (model) on the application importance.
For the above points, GIS in the study may be more and more as the data model of the boarding platform and the carrier, the application is more similar to the GIS database as an underlying structure; Open importance is obvious, but the database comparison, GIS long way to go; for the third point, for the country, may have started to change, but only the beginning. MapGIS perhaps a very good example. The fourth point is very important, the choice of data structure or model is critical for applications, program design so, GIS application of the case. Because both the abstract data are realistic.
Geodatabase using feature (feature) data sets and feature class to represent vector data, raster data sets used to represent raster data, TIN data sets to express the three-tier network.
Modeling of the most important decision is to choose the right data expression. Vector, raster and surface (TIN) representation of advantages and disadvantages. Analysis is more suitable for raster data, location, management, on the contrary, the actual work can be used in combination. Resolution (scale) is a must to consider.
Geographic data structure. Describes the geographic data in the computer organization. First, the data can exist in a database or folder, corresponding to different connections. Geodatabase equivalent to a database is a collection of such data sets.
This chapter describes the so-called Feature, that is, a class of geographic objects, and in the GIS for the point, line, face shape, there are geo-referenced (location), have properties and behavior. The property is a database field, there are some types. Mainly refers to a number of behavioral rules, similar to the database rules, topology, etc., and can be programmed to implement other behavior. Inside the database, feature only a table, its object is a table row, but for applications, is equivalent to the database OR Mapping, of great significance.
Database through the data set, Feature (including vector, raster, and custom) to organize such a hierarchy, and between the different Feature can be defined as a database table relationships. Feature need custom COM interfaces.
ArcGIS is a general feeling that a lot of things starting point, the idea is good, but difficult to use. There are similar products of companies like IBM. This product is for policy makers, senior staff may be good for, but for the average developer, it is not a good thing. One reason is that the success of Microsoft developer-friendly, then, GIS industry?
Characteristics of the shape of the
Through the implementation of the database using the version of the work flow, good ideas, practical applications? If you need to merge or update the parent version of how to do a lot of conflict? Do not have the practical experience, hard to say.
Through the release, another reason is that the reasons for the so-called Temporal GIS for land application of this industry, this version of the database, may be able to solve many problems. As just speculation.
Network consists of edges and nodes. Said roads, pipelines, water, electricity and so on. There are 2 views: logical and geometric networks. The former is equivalent to a graph data structure. Network analysis by solving network problems.
There are many sources of raster data, such as remote sensing images. Raster data can generally be divided into thematic data and image data, the former expressed by the actual value of certain parameters, such as land use, slope, etc.; the latter obtained through some kind of imaging device. Grid can be used as base maps, land use, hydrology, environmental analysis, terrain analysis and other purposes.
The lattice grid can save different properties, such as name, number, order, proportion. Grid computing can be done by a lot of problems. Quickly through the grid to display an image pyramid.
Raster data structure from both a theoretical point of view or practical point of view, are more suitable for analysis of a data structure. But commercial software support for raster data structure is relatively weak.
Surface models are now slowly instead of using the grid structure of the Tin.
Is the nature of the location attribute to find the geographic coordinates. Needs to be done in this area, such as LBS, you can see.
Spatial database design, database design and general no major difference.
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