1:250,000 National Basic Geographic Data Introduction
The national 1:250,000 public version of the basic geographical data covers the country's land area and major islands including Taiwan Island, Hainan Island, Diaoyu Islands, and South China Sea Islands, as well as their adjacent waters, with a total of 816 pieces . The geospatial reference adopts the 2000 National Geodetic Coordinate System, the 1985 National Elevation Datum, and the latitude and longitude coordinates. The entire set of data has been processed using map confidentiality technology to keep the spatial location accuracy and attribute content confidential. Its spatial location accuracy and attribute content comply with the "Several Provisions on the Representation of Public Map Content", the "Supplementary Provisions on the Representation of Public Map Content" and the "Disclosure Representation of Basic Geographic Information" Content Regulations".
While ensuring national security, actively promote the social application of basic surveying and mapping results to meet the growing public demand for basic geographical data. With the approval of the Ministry of Natural Resources, the "National Geographic Information Resources Catalog Service System" now provides free data download services at a scale of 1:250,000 and keeps the data version continuously updated. At present, the downloaded data is provided using the **1:250,000 standard map, and the overall current situation is 2015; the layer content includes water systems (points, lines, and surface layers), highways, railways (line layers), and residential areas (points, lines, and surface layers). Surface layer), residential place names (note points), natural place names (note points)** and other 9 types of element layers.
Since what is provided for download is the original vector data, not the final map, there are certain differences in visual expression between it and the symbolized map. Therefore, users who use downloaded geographical information data to compile maps must strictly implement the relevant provisions of the "Map Management Regulations"; if the compiled maps need to be disclosed to the public, they must also perform map review procedures in accordance with the law.
CnOpenData has obtained permission from the National Basic Geographic Information Center to include 1:250,000 national basic geographical data in the public data section for the convenience of scholars. To download data, please go to National Geographic Information Resources Directory Service System.
The content of this page is transferred from the National Geographic Information Resources Directory Service System, the URL is www.webmap.cn .
Result specifications
- Frames and numbers
1: The total number of maps in the 250,000 public version of the basic geographical information data is 816, and the slicing data is implemented in accordance with GB/T 13989-2012 "National Basic Scale Topographic Map Scattering and Numbering". Spatial storage unit: 15′ (longitudinal difference) × 10′ (dimensional difference).
- Geospatial Reference
- Plane coordinate system: 2000 National Geodetic Coordinate System.
- Height benchmark: 1985 National Height Benchmark.
- Map projection: The framed data uses geographical coordinates, and the coordinate unit is degrees.
- Geometry Accuracy
After the update, the plane position and elevation errors of the nearby field control points meet the requirements of the table below, with twice the error as the maximum error.
| Category | Error in plane (unit: meter) | Error in plane (unit: meter) | Error in plane (unit: meter) | Error in elevation (unit: meter) | Error in elevation (unit: meter) | | ---- | ---- | ---- |---- |---- | | Classification | Level 1 | Level 2 | Level 3 | Note points | Contour lines | | Flat | 125 | 150 | 200| 2.5| 3.0| | Hilly | 125 | 150 | 200| 4.0| 5.0|
Outcome data organization
The 1:250,000 public version of basic geographic data currently available for download consists of 4 data sets and 9 data layers.
The name of the data layer uses four characters. The first character represents the data classification, the second and third characters are the abbreviation of the data content, and the fourth character represents the geometry type.
| Element classification | Data tiering | Data tiering | Geometry type | Main elements |
|---|---|---|---|---|
| Water system (H) | Water system (surface) | HYDA | Noodles | Lake, reservoir, double-line river, etc. |
| Water system (H) | Water system (line) | HYDL | Line | Single-line rivers, ditches, river structure lines, etc. |
| Water system (H) | Water system (point) | HYDP | Point | Springs, wells, etc. |
| Residential area and facilities (R) | Residential area (area) | RESA | Noodles | Residence |
| Residential area and facilities (R) | Residential place (point) | RESP | Point | Ordinary houses, yurts, grazing spots, etc. |
| Transportation (L) | Railway | LRRL | Line | Standard gauge railway, narrow gauge railway, etc. |
| Transportation (L) | Highway | LRDL | Line | National roads, provincial roads, county roads, rural roads, other roads, streets, rural roads, etc. |
| Place names and notes (A) | Residential place name (point) | AGNP | Point | Administrative place names at all levels and names of urban and rural residential areas, etc. |
| Place names and notes (A) | Natural place name (point) | AANP | Point | Transportation element names, memorial and historic site names, mountain names, water system names, marine area names, natural area names, etc. |