Location in data pipelines.
WHAT THE TYPES ARE
- Points: a single location
- Lines: routes and paths
- Polygons: areas and boundaries
WHAT A COORDINATE REFERENCE SYSTEM IS
The model describing how coordinates map to positions on the earth.
WHY IT MATTERS ENORMOUSLY
Coordinates in different systems refer to different places, and mixing them produces errors of considerable distance.
WHAT TO RECORD
The reference system, always.
WHAT THE COMMON DEFAULT IS
A global system used by positioning devices and web mapping.
WHAT PROJECTION AFFECTS
Distance and area calculations, which are distorted differently by each.
WHAT THAT MEANS
Measuring distance in degrees is wrong.
WHAT TO USE
A geographic type that calculates on the earth's surface, or an appropriate projected system.
WHAT SPATIAL DATABASES PROVIDE
Geometry types Spatial indexes
Operations: containment, intersection, distance, buffering
WHAT SPATIAL INDEXES ENABLE
Finding what is nearby without scanning everything.
WHAT COMMON OPERATIONS ARE
Which area contains this point What is within a distance Where do these overlap
WHAT TO BE CAREFUL WITH
Address data, which is inconsistent and requires geocoding Boundaries changing over time
WHAT TO RECORD
When a boundary set applies from.
