The GeoSOT grid

Instructions for use

The GeoSOT grid, The GeoSOT (Geographic Coordinate Subdividing Grid with One Dimension Integral Coding on 2n-Tree ) is a global longitude-latitude subdivision grid based on a 2n-dimensional integer array.

With the development of Spatial Info industry, the contents of Spatial Data in different industries are specialized, various and relational, and their production and maintenance are often scattered in different units, resulting in different data grid standards adopted between different departments and different systems. Although the establishment of independent data organization and Index Type in different departments can well meet the business needs of the department, in the cross-departmental data application, different data organization and recording methods bring great invariability, which is not conducive to the exchange and sharing of Spatial Info.

GeoSOT global longitude and latitude subdivision grid is a grid system based on Geographic Coordinate System, which can seamlessly cover the whole world, and the connection between grids is more uniform and stable. Its subdivision grid has the characteristics of identifiability, hierarchy, aggregation and relevance, and can realize the organic association between levels. And provide a basis for map multi-scale expression. The grid is divided by longitude and latitude, so it can be well aggregated and associated with the national standard map, and can be easily converted with the current main types of data, which is conducive to the compatibility of multi-source data and the integration and sharing of Spatial Data across departments and systems.

The GeoSOT grid is subjected to three times of spatial expansion (the geographic space of the earth is expanded to 512 °, 1 ° is expanded to 64 ′, and 1 ′ is expanded to 64 ″) through the longitude and latitude range space of the earth surface, so as to realize the integer quadtree grid division of integer degree and integer division. The specific grid division method is as follows:

  • The first expansion: First, transform the earth into a plane through simple projection, expand 180 ° × 360 ° to 512 ° × 512 °, as the zero-level section, take the prime meridian and the equator as the intersection point as the center point, recursively quadrangle until the 1 ° grid unit, as shown in Figure 1, which can also be called the degree-level grid. This subdivision includes 10 levels, namely, 0-9 levels.
    • The 0-level grid is a 512 ° × 512 ° cell centered at the intersection of the prime meridian and the equator. The 0-level grid is coded as G, which means Globe, as shown in Figure a.
    • The first level grid is divided into four parts on the basis of the zero level grid, and the size of each grid is 256 ° × 256 °; the first level grid is coded as Gd, where d is 0, 1, 2 or 3. As shown in Figure B, G0 corresponds to the position of the Spatial Info area in the northeast hemisphere.
    • The second level grid is divided equally into four parts based on the first level grid, and the size of each grid is 128 ° × 128 °. Level 2 trellis code is Gdd, where d is 0, 1, 2, or 3. As shown in Figure C, G00 corresponds to the most part of the Northeast Hemisphere in the Spatial Info area. In the second-level subdivision grid, some grids have no actual geographical significance, such as G02 and G03, and are not divided; other second-level grids enter the division of the next level grid as a whole, and the division of the next level grid is the same.

      Some level 2 grids have no actual geographical significance and are no longer divided downward, such as As shown in figure C. Although some areas of the other level 2 grids fall into reality, Beyond the international geographical area, it can still be carried out as a whole. This principle is also applicable to the division of the following grids. Points.

    • The third level grid is divided equally into four parts based on the second level grid, and the size of each grid is 64 ° × 64 °; the third level grid is coded as Gddd, where d is 0, 1, 2 or 3. As shown in Figure d, G001 corresponds to China, India and Southeast Asia in the Spatial Info area.
      • The principle of mesh generation of the
    • lower layer is analogized.

  • 2nd expansion: Expand the 1 ° grid unit from 60 ′ to 64 ′, and then recursively quad-divide to 1 ′ grid unit. It can also be called the hierarchical subdivision grid. This subdivision includes 6 levels, that is, 10 to 15 levels. The 10th level grid is defined to be divided into four parts on the basis of the root node of the hierarchical grid. The size of each grid is 32 ′ × 32 ′. The code of the 10th level grid is Gddddddddd-m, where d and m are quaternary numbers of 0, 1, 2 or 3. The principle of mesh generation of the lower layer is analogized.
  • 3rd expansion: Expand the 1 ° grid unit from 60 ″ to 64 ″, and then recursively quad-divide to 1 ″ grid unit. Dividing units below 1 ″ are directly divided by four branches, up to 32 levels. The second-level subdivision grid is divided from the 16th level to the 21st level, and the root node of the second-level grid is in one-to-one correspondence with the 15th level grid (1 ′ grid or 60 ″ grid), and the code is the same, and the grid size is expanded from 60 ″ to 64 ″, as shown in fig. 3. GeoSOT second subdivision begins at the 16th level of the grid and is defined as an average of four divisions based on the root node of the second level grid. The 16th level trellis code is in the form of: Gddddddddd-mmmmmm-s, where d, m, and s are quaternary numbers with values of 0, 1, 2, or 3. The principle of mesh generation of the lower layer is analogized.
    • The grids of 22-32 levels below the
  • second are divided and coded strictly according to the quartering method.

According to the above definition of subdivision level, GeoSOT Grid is divided into 32 levels, ranging from global to centimeter, and evenly divides the earth's surface space into multi-level grids, which form a global quadtree system. The area ratio between the upper and lower levels of the GeoSOT Grid is roughly 4:1, which varies evenly. The number of GeoSOT grids at all levels and the approximate spatial scale size on the ground are shown in Table 1.

GeoSOT Partition Frame Level Features

Geo mesh unit subdivision code

According to the subdivision principle of GeoSOT Grid, the GeoSOT Grid code is used to identify the subdivision grid at all levels with 64-bit code.

The longest encoding bit is a 32-bit quaternary numeric encoding. Bits 1 to 9 are degree-level trellis codes, bits 10 to 15 are hierarchical trellis codes, bits 16 to 21 are second-level trellis codes, bits 22 to 32 are trellis codes below second, and the code length is the trellis level.

The quaternary 1-D code of the GeoSOT grid starts with G, the codes at the degree, minute and second levels are separated by "-", and the codes below the second level are separated by ".", in the form of "Gddddddddd-mmmmmm- ssssss. Uuuuuuuuuuu". Where d, m, s, u take the values 0, 1, 2, 3. The specific coding rule is that the nearest grid to the intersection of the equator and the prime meridian is 0, the farthest grid is 3, and then the other two grids are 1 and 2 respectively along the latitude direction and then along the longitude direction.

Encoding of GeoSOT Grid units

With this Encode Type, each GeoSOT grid cell is encoded and the encoding is globally unique. At the same time, because each grid in the GeoSOT grid has a certain geographic Spatial Range on the earth, the GeoSOT grid unit section code has an accurate geographic spatial meaning, and can have the meaning of geographic spatial coordinates to some extent.

Function entrance

  • Open Map in Current Works pace, Map tab-> Drawing group-> GeoSOT Grid.
  • Data tab-> Data Processing group-> Map Cartography-> GeoSOT Grid.

Parameter Description

  • Start Level: Set the start level of the generated grid. The value range is 0, end level. The default is 0, that is, the start level is level 0.
  • End Level: Set the end level of the generated grid. The value range is Start Level, 32. The start level and the end level are supported to be consistent, which is convenient for the user to generate only one level of grid.
  • Range Type: The range only supports the range under the Geographic Coordinate System. Three range types are available: Global, National Area and User-defined. If Custom Bounds "is selected, Map Range can be defined by entering the coordinates of the four corners in the upper left and lower right text boxes, and Bounds Settings can also be defined through the four Function Buttons on the right.
    • Whole Map: The full range of the currently opened map, which can be viewed in the "Map Properties" panel through the Full View operation of the map.
    • Current Windows: The view range of the currently opened map. You can adjust the Current View by zooming in, zooming out, and modifying the scale of the map.
    • Copy: You can copy the four range values on the left to the clipboard, or directly paste the copied results to other places that support Bounds Settings, such as Dataset Bounds in the Dataset attribute panel.
    • Paste: Copy the four range values in the clipboard to the four text boxes at the top left and bottom right of the dialog box.

After the Parameter Settings are completed, the GeoSOT grid can be generated. After the generation is successful, the program will add the Result Dataset to the new Map for viewing by default.

Application example

Taking the World _ Google map in SuperMap Sample Data SampleData-> World-> World Workspace as an example, the GeoSOT Grid of 0-3 levels and Global is generated.

As a result, a total of four levels of grid maps are generated. The code and GeoSOT level of a single grid are recorded in the Layer Properties table of each level of grid, and the Unique-values Map is made with Code code and superimposed on the map to obtain the results as shown in the following figure. If

part of the area falls outside the actual geographical area, the program will clip this part of the grid and only retain the data within the effective geographical area, such as G11, G01, G21, G31 in the second-level grid, and G112, G103, 312, G303 and other edge grids in the third-level grid.

GeoSOT Grid results