A government agency wants to publish an interactive flood risk map that citizens can query by address. Which Web GIS architecture would serve this need?
AEmail PDF maps to all residents
BA web mapping application with a tile base map, a WMS/WFS layer serving flood zone polygons from a spatial database, geocoding for address search, and identify/query tools for parcel-level flood risk information
CInstall desktop GIS software on every citizen's computer
DA static image of the flood map posted on the agency website
This requires an interactive web application combining a base map for context, flood data served dynamically so it stays current, geocoding to convert addresses to map locations, and query capability to retrieve flood risk attributes for specific parcels. This architecture serves unlimited users through browsers without software installation or GIS expertise.
Question 2 True / False
WMS (Web Map Service) and WFS (Web Feature Service) return the same type of data.
TTrue
FFalse
Answer: False
WMS returns pre-rendered map images (PNG/JPEG) -- the client receives a picture and cannot query individual features. WFS returns the actual vector feature data (GML/GeoJSON) with geometry and attributes, allowing the client to query, filter, style, and analyze features. WMS is simpler and faster for display; WFS provides full data access for interactive applications. The choice depends on whether the client needs to just view or also interact with the data.
Question 3 Short Answer
Explain what tile-based web mapping is and why it transformed web GIS performance.
Think about your answer, then reveal below.
Model answer: Tile-based mapping pre-renders the map at multiple zoom levels as grids of small image tiles (typically 256x256 pixels). Instead of rendering the entire map for each request, the server serves only the tiles visible in the current view extent, and clients cache tiles for reuse. This transformed performance because: (1) rendering is done once at build time, not per request; (2) only visible tiles are transferred, reducing bandwidth; (3) clients cache tiles locally, eliminating redundant requests; (4) tiles from different zoom levels enable smooth multi-scale navigation. Vector tiles extend this concept by serving pre-tiled vector data that clients render dynamically.
Tiling converts an impossibly expensive render-on-demand problem into a manageable serve-from-cache problem, enabling fluid map interaction that feels like panning across a continuous surface.