in the column and its type declaration like:

geom GEOMETRY (Point, 4326)

what does 4326 mean?

The unit is in ________.

Question

in the column and its type declaration like:

geom GEOMETRY (Point, 4326)

what does 4326 mean?

The unit is in ________.

BlackTom AI · Accepted Answer

4326 is the SRID/EPSG code for the WGS84 geographic coordinate system, which uses angular units — so the unit is degrees.

1) Relevant knowledge points and concepts
- The second value in geom GEOMETRY(Point, 4326) is the SRID (spatial reference identifier), commonly an EPSG code.
- EPSG:4326 corresponds to the WGS84 geographic CRS (latitude/longitude).
- Geographic CRSs express positions as angles (degrees of latitude and longitude), not linear units like meters.

2) Step-by-step reasoning
- The GEOMETRY declaration includes a numeric SRID to tell the database which coordinate reference system the coordinates use.
- SRID 4326 is the standard identifier for WGS84 (EPSG:4326).
- WGS84 coordinates are given as longitude and latitude in decimal degrees (e.g., -122.4194, 37.7749).

3) Calculation examples and intermediate steps
- To understand scale: Earth's approximate equatorial circumference ≈ 40,075 km.
- One degree of latitude ≈ 40,075 km / 360 ≈ 111.32 km per degree.
- Therefore 0.01° ≈ 1.1132 km, showing how angular degrees map to distance depending on location.

4) Why the correct answer is correct
- Because SRID 4326 explicitly designates a geographic (angular) coordinate system, the coordinates are expressed in degrees of latitude/longitude rather than meters/feet. Databases (PostGIS, spatial libraries) interpret stored numeric coordinates under that CRS as decimal degrees.

5) Why other possible units (meters, kilometers, feet, radians) are incorrect
- Meters/kilometers/feet apply to projected (planar) CRSs such as UTM or Web Mercator (e.g., EPSG:3857 uses meters).
- Radians are a theoretical angular unit but are not used by EPSG:4326; WGS84 uses decimal degrees.
- Assuming linear units would cause incorrect distance/area calculations unless coordinates are reprojected into a projected CRS.

6) Conclusion
- The unit for GEOMETRY(Point, 4326) is degrees — confirming the provided answer: degrees.

in the column and its type declaration like: geom GEOMETRY (Point, 4326) what does 4326 mean? The unit is in ________. 单项选择题

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