🗺️Geospatial Engineering Unit 9 – Web Mapping & Geospatial Services

Key Concepts and Terminology

• Web mapping involves creating interactive maps accessible through web browsers
• Geospatial data represents real-world features with geographic coordinates (latitude, longitude)
• Vector data uses points, lines, and polygons to represent discrete features (roads, buildings)
• Raster data uses a grid of pixels to represent continuous data (satellite imagery, elevation)
• Spatial reference systems define how geographic coordinates relate to locations on the Earth's surface
  • Common systems include WGS84 and NAD83
• Map projections transform the Earth's curved surface onto a flat plane (Mercator, UTM)
• Tiling divides maps into smaller, manageable pieces for efficient loading and display
• Symbology refers to the visual representation of map features using colors, icons, and styles

Web Mapping Basics

• Web maps are interactive maps accessed through a web browser
• They allow users to pan, zoom, and interact with geospatial data
• Web maps are composed of map layers, each representing a specific dataset or theme
• Basemaps provide a background reference for context (streets, satellite imagery)
• Layers can be toggled on and off to customize the map view
• Map controls enable user interaction (zoom buttons, layer switcher)
• Web maps are responsive, adapting to different screen sizes and devices
• They can incorporate real-time data and updates for dynamic visualization

Geospatial Data Formats and Standards

• GeoJSON is a lightweight format for encoding vector data using JSON syntax
  • It supports points, lines, polygons, and multi-part geometries
• KML (Keyhole Markup Language) is an XML-based format for geographic data
  • It is commonly used for displaying data in Google Earth and other applications
• Shapefile is a popular vector data format that includes geometry and attributes
  • It consists of multiple files (.shp, .dbf, .shx) that must be used together
• GeoTIFF is a raster format that embeds geospatial metadata within a TIFF image file
• WMS (Web Map Service) is a standard protocol for serving georeferenced map images over the web
• WFS (Web Feature Service) allows querying and retrieval of vector data over the web
• OGC (Open Geospatial Consortium) develops and maintains open standards for geospatial data and services

Web Mapping Technologies and Platforms

• JavaScript libraries like Leaflet and OpenLayers enable interactive web mapping
  • They provide APIs for loading data, rendering maps, and handling user interactions
• Mapbox is a platform that offers customizable basemaps, styling tools, and APIs for web and mobile mapping
• ArcGIS Online is a cloud-based platform for creating, sharing, and managing web maps and geospatial data
• QGIS is an open-source desktop GIS application that supports web mapping through plugins and integrations
• GeoServer is an open-source server for publishing geospatial data and services (WMS, WFS)
• PostGIS is a spatial database extension for PostgreSQL that enables storage and querying of geospatial data
• Mapbox GL JS is a JavaScript library for rendering interactive, customizable vector maps using WebGL

Creating Interactive Web Maps

• Define the purpose and audience of the web map to guide design decisions
• Choose an appropriate basemap that provides context and complements the map's theme
• Prepare and optimize geospatial data for web delivery (simplify geometries, reduce file sizes)
• Use JavaScript libraries or platforms to load and display the data on the web map
• Apply appropriate symbology and styling to enhance the visual representation of features
  • Use colors, icons, and labels to convey information effectively
• Implement interactive features like popups, tooltips, and layer controls
  • Popups can display attribute information when features are clicked
• Optimize performance by using techniques like data compression, caching, and lazy loading
• Test the web map on different devices and browsers to ensure compatibility and responsiveness

Geospatial Services and APIs

• Geospatial services provide access to geospatial data and functionality over the web
• REST (Representational State Transfer) is a common architectural style for designing web services
  • REST APIs use HTTP methods (GET, POST, PUT, DELETE) for data retrieval and manipulation
• WMS (Web Map Service) serves georeferenced map images that can be displayed in web maps
  • WMS requests specify the layers, extent, and image format to be returned
• WFS (Web Feature Service) allows querying and retrieval of vector data over the web
  • WFS supports filters and spatial queries to select specific features
• Geocoding services convert addresses or place names into geographic coordinates (forward geocoding)
  • Reverse geocoding converts coordinates into human-readable addresses
• Routing services calculate optimal routes between locations based on transportation networks and constraints
• Geospatial APIs provide programmatic access to geospatial data and services
  • Examples include Google Maps API, Mapbox API, and ArcGIS API for JavaScript

Data Visualization Techniques

• Choropleth maps use color gradients to represent statistical data aggregated by geographic areas
  • Commonly used for visualizing demographic, economic, or environmental data
• Proportional symbols use scaled symbols (circles, squares) to represent quantitative data at specific locations
  • Symbol size is proportional to the data value
• Heat maps show the density or intensity of point data using a color gradient
  • Useful for visualizing patterns and clusters in large datasets
• Clustering groups nearby points into a single symbol to reduce visual clutter
  • Clusters can be dynamically expanded or collapsed based on zoom level
• 3D visualization adds depth and perspective to maps, enhancing the representation of terrain, buildings, or other features
  • Can be achieved using libraries like Cesium or Three.js
• Animated maps display time-series data or represent change over time
  • Can show the movement of objects, the spread of phenomena, or the evolution of patterns
• Interactive charts and graphs can be integrated with web maps to provide additional data exploration capabilities
  • Examples include bar charts, line graphs, and pie charts

Practical Applications and Case Studies

• Urban planning: Web maps can be used to visualize land use, zoning, and infrastructure data for urban planning and decision-making
• Emergency response: Real-time web maps can help emergency responders track incidents, allocate resources, and plan evacuation routes
• Environmental monitoring: Web maps can display sensor data, satellite imagery, and model outputs for monitoring air quality, water resources, and natural hazards
• Business analytics: Web maps can be used to analyze market trends, customer demographics, and site selection for business intelligence
• Transportation: Web maps can provide real-time traffic information, transit schedules, and routing services for transportation planning and navigation
• Public engagement: Interactive web maps can facilitate public participation in planning processes, allowing citizens to explore data, provide feedback, and contribute local knowledge
• Cultural heritage: Web maps can showcase historical maps, archaeological sites, and cultural resources for education and preservation purposes
• Social media integration: Web maps can be integrated with social media platforms to display user-generated content, such as geotagged photos or tweets, providing insights into social trends and sentiments