Skip to main content

Geographic Database Design in GIS


Geographic database design means planning how spatial data (maps + attributes) will be stored in a GIS system.

It is done in three main phases:

  1. Conceptual Design → What data is needed?

  2. Logical Design → How should data be structured?

  3. Physical Design → How will it be implemented in software?

Conceptual Database Design (The "WHAT" Phase)

🔹 Meaning

This is the high-level planning stage.
It focuses on understanding real-world geographic features and their relationships.

It is independent of any software (not linked to PostgreSQL, ArcGIS, etc.).

🔹 Key Terminologies

  • Entity → A real-world object
    Example: River, Road, Building, Village

  • Attribute → Information about an entity
    Example:

    • River → Name, Length

    • Road → Type, Width

  • Relationship → How entities are connected
    Example:

    • Road crosses River

    • Village located near River

  • ER Diagram (Entity-Relationship Diagram)
    A diagram that shows entities, attributes, and relationships.

🔹 Object-based vs Field-based Model

TypeMeaningExample
Object-based modelDiscrete featuresRoad, School, Lake
Field-based modelContinuous surfaceTemperature, Elevation, Rainfall

✔ In your rainfall or TWI analysis work, rainfall is a field model (continuous surface).
✔ In urban footprint extraction (Palakkad project), buildings are object model.

🎯 Goal of Conceptual Design

Define:

  • What data is needed?

  • What features exist?

  • How are they related?

Logical Database Design (The "HOW" – Abstract Phase)

🔹 Meaning

Now we convert the conceptual idea into a structured data model.

Still independent of specific software, but more technical.

🔹 Key Terminologies

1. Spatial Data Types (Geometry Types)

Geometry TypeExample
PointBorewell location
LineRoad, River
PolygonVillage boundary
RasterElevation map, NDVI map

2. Table Structure

Entities become tables

Example:

Table: Road

Road_IDNameTypeGeometry

3. Primary Key

A unique ID for each feature.

Example:
Road_ID → uniquely identifies each road.

4. Foreign Key

Links one table to another.

Example:
Village table contains District_ID to connect with District table.

5. Normalization

Organizing tables to:

  • Avoid duplication

  • Reduce redundancy

  • Improve data integrity

Example:
Instead of repeating district name in every village record → create a separate district table.

6. Topology (Spatial Relationships)

Defines spatial rules like:

  • Connected to

  • Adjacent to

  • Within

  • Contains

  • Intersects

Example:

  • Road must be connected at junctions

  • Building must be inside municipal boundary

In your GIS work, topology helps avoid:

  • Gaps

  • Overlaps

  • Duplicate boundaries

🎯 Goal of Logical Design

Create:

  • Tables

  • Fields

  • Keys

  • Spatial relationships

  • Clean data structure

Physical Database Design (The "HOW" – Technical Phase)

🔹 Meaning

Now the database is implemented in a real GIS-enabled DBMS.

Examples:

  • PostgreSQL + PostGIS

  • Oracle Spatial

  • ArcGIS Geodatabase

  • SpatiaLite

🔹 Key Terminologies

1. Data Types

Example in PostGIS:

geometry(Point, 4326)  geometry(Polygon, 32643)

  • GEOMETRY → planar coordinates

  • GEOGRAPHY → earth-based spherical coordinates

2. Spatial Index

To make spatial queries fast.

Example:

  • R-Tree Index

  • GiST Index (PostGIS)

Used for:

  • Finding nearest road

  • Intersect queries

  • Buffer analysis

3. SQL Implementation

Example:

CREATE TABLE roads (    road_id SERIAL PRIMARY KEY,    name VARCHAR(50),    type VARCHAR(20),    geom GEOMETRY(LineString, 4326)  );

4. Optimization

Includes:

  • Indexing

  • Clustering

  • Storage tuning

Improves:

  • Query speed

  • Performance

  • Large dataset handling

🎯 Goal of Physical Design

Create:

  • Real tables

  • Spatial columns

  • Indexes

  • Efficient storage

Summary 

PhaseFocusQuestion AnsweredOutput
ConceptualReal-world understandingWhat data is needed?ER Diagram
LogicalData structureHow should data be organized?Tables & schema
PhysicalImplementationHow to implement in DBMS?SQL tables & indexes

Simple Real Example (Village Mapping Project)

Step 1 – Conceptual

Identify:

  • Village

  • Road

  • River

  • Relationships

Step 2 – Logical

Create tables:

  • Village table

  • Road table

  • River table

Define:

  • Primary keys

  • Geometry types

  • Topology rules

Step 3 – Physical

Implement in:

  • QGIS Geopackage

  • PostGIS database

Create:

  • Spatial index

  • Constraints

  • SQL structure

Comments

Post a Comment

Popular posts from this blog

Atmospheric Window

The atmospheric window in remote sensing refers to specific wavelength ranges within the electromagnetic spectrum that can pass through the Earth's atmosphere relatively unimpeded. These windows are crucial for remote sensing applications because they allow us to observe the Earth's surface and atmosphere without significant interference from the atmosphere's constituents. Key facts and concepts about atmospheric windows: Visible and Near-Infrared (VNIR) window: This window encompasses wavelengths from approximately 0. 4 to 1. 0 micrometers. It is ideal for observing vegetation, water bodies, and land cover types. Shortwave Infrared (SWIR) window: This window covers wavelengths from approximately 1. 0 to 3. 0 micrometers. It is particularly useful for detecting minerals, water content, and vegetation health. Mid-Infrared (MIR) window: This window spans wavelengths from approximately 3. 0 to 8. 0 micrometers. It is valuable for identifying various materials, incl...
Post a Comment
Read more

Energy Interaction with Atmosphere and Earth Surface

In Remote Sensing , satellites record electromagnetic radiation (EMR) that is reflected or emitted from the Earth. Before reaching the sensor, radiation interacts with: The Atmosphere The Earth's Surface These interactions control how satellite images look and how we interpret them. I. Interaction of EMR with the Atmosphere When solar radiation travels from the Sun to the Earth, four main processes occur: 1. Absorption Definition: Absorption occurs when atmospheric gases absorb radiation at specific wavelengths and convert it into heat. Main absorbing gases: Ozone (O₃) → absorbs Ultraviolet (UV) Carbon dioxide (CO₂) → absorbs Thermal Infrared Water vapour (H₂O) → absorbs Infrared Concept: Atmospheric Windows These are wavelength regions where absorption is very low, allowing radiation to pass through the atmosphere. Remote sensing depends on these windows. For example, satellites like Landsat 8 use visible, near-infrared, and thermal bands located in atmospheric windows. 2. Trans...
Post a Comment
Read more

Platforms in Remote Sensing

In remote sensing, a platform is the physical structure or vehicle that carries a sensor (camera, scanner, radar, etc.) to observe and collect information about the Earth's surface. Platforms are classified mainly by their altitude and mobility : Ground-Based Platforms Definition : Sensors mounted on the Earth's surface or very close to it. Examples : Tripods, towers, ground vehicles, handheld instruments. Applications : Calibration and validation of satellite data Detailed local studies (e.g., soil properties, vegetation health, air quality) Strength : High spatial detail but limited coverage. Airborne Platforms Definition : Sensors carried by aircraft, balloons, or drones (UAVs). Altitude : A few hundred meters to ~20 km. Examples : Airplanes with multispectral scanners UAVs with high-resolution cameras or LiDAR High-altitude balloons (stratospheric platforms) Applications : Local-to-regional mapping ...
Post a Comment
Read more

Scattering

Scattering 
Post a Comment
Read more

History of GIS

1. 1832 - Early Spatial Analysis in Epidemiology:    - Charles Picquet creates a map in Paris detailing cholera deaths per 1,000 inhabitants.    - Utilizes halftone color gradients for visual representation. 2. 1854 - John Snow's Cholera Outbreak Analysis:    - Epidemiologist John Snow identifies cholera outbreak source in London using spatial analysis.    - Maps casualties' residences and nearby water sources to pinpoint the outbreak's origin. 3. Early 20th Century - Photozincography and Layered Mapping:    - Photozincography development allows maps to be split into layers for vegetation, water, etc.    - Introduction of layers, later a key feature in GIS, for separate printing plates. 4. Mid-20th Century - Computer Facilitation of Cartography:    - Waldo Tobler's 1959 publication details using computers for cartography.    - Computer hardware development, driven by nuclear weapon research, leads to broader mapping applications by early 1960s. 5. 1960 - Canada Geograph...
Post a Comment
Read more