21/09/2025
Getting Started with Data Management
1. Introduction to GIS Data
Data is the foundation of any GIS.
Spatial data is different from regular data because it includes x,y coordinates that represent the real-world location of a phenomenon.
With spatial data, you can:
Visualize real-world features on maps.
Perform spatial analysis (proximity, buffering, measurement).
Select features by location.
Calculate properties such as area and length.
2. Types of Spatial Data (Raster vs. Vector)
🔹 Vector Data
Represents real-world features using:
Points: clinics, poles.
Lines: roads, rivers.
Polygons: parcels, buildings.
Includes attributes that describe each feature.
🔹 Raster Data
A grid of cells (pixels), each with a value (elevation, temperature, etc.).
Best for continuous phenomena such as elevation, rainfall, or temperature.
Includes:
Satellite imagery.
Scanned maps.
Derived rasters (e.g., slope, aspect, hillshade).
3. Coordinate Systems
Every x,y coordinate must be tied to a coordinate system.
Types:
Geographic Coordinate Systems (lat/long): e.g., NAD 1927.
Projected Coordinate Systems (State Plane): provide higher accuracy for local areas.
UTM (Universal Transverse Mercator): divides the globe into zones for minimized distortion.
4. Metadata
Metadata is the “data about the data.”
Provides: description, author, creation date, accuracy, keywords.
Helps assess whether a dataset is suitable for your task.
Example: Sentinel-2 imagery includes pixel size (10m, 20m, 60m), update frequency, and potential applications.
5. Editing GIS Data
You can edit both:
Geometry: shape and location of points, lines, or polygons.
Attributes: non-spatial information in the attribute table.
Permissions are controlled by dataset creators or administrators.
6. Maintaining Data Integrity
To minimize errors during editing, GIS uses data behaviors:
Domains: predefined lists of valid attribute values (e.g., road type = Local, Collector, Arterial).
Subtypes: subsets of features with shared attributes (e.g., default speed limit for different road types).
Topology: rules that maintain spatial relationships (connectedness, adjacency, containment).
Archiving: stores past versions of data, allowing temporal analysis of how geometry and attributes have changed over time.
7. Using Non-GIS Data in GIS
Not all data starts as GIS data, but it can be integrated if location info exists:
Spreadsheets (Excel): addresses, administrative divisions, or x,y coordinates.
Databases (SQL, Oracle): connected directly to GIS.
Business Intelligence (Power BI): can include Esri maps for enhanced analysis.
Unstructured Data (PDFs, reports, social media): ArcGIS can extract place names or coordinates and plot them instantly on maps.
✅ Key Takeaways
This course teaches you to:
Understand the difference between spatial and non-spatial data.
Differentiate raster and vector data types.
Apply coordinate systems for accurate mapping.
Use metadata to evaluate data quality.
Perform editing tasks on geometry and attributes.
Maintain data integrity with domains, subtypes, and topology.
Integrate non-GIS data into GIS workflows.
