Project 4: Map and Location-Based App

Build a geospatial ChatGPT App that combines map interaction, location tools, and resilient fallbacks.

Quick Reference

Attribute Value
Difficulty Intermediate
Time Estimate 1-2 weeks
Main Programming Language TypeScript
Alternative Programming Languages Python, Kotlin
Coolness Level Level 4
Business Potential High
Prerequisites Geospatial basics, API failure handling
Key Topics Geocoding, viewport queries, map/list sync

1. Learning Objectives

  1. Build viewport-aware map queries.
  2. Synchronize map markers and list panels.
  3. Handle geospatial uncertainty and API outages.
  4. Present route/ETA information with confidence cues.

2. All Theory Needed (Per-Concept Breakdown)

Geospatial Data Reliability in Conversational Interfaces

Fundamentals Geospatial systems are probabilistic: geocoding can be approximate, APIs can disagree, and coordinates can drift in precision. Users need clarity on confidence and data source recency.

Deep Dive into the concept Design geospatial flows with explicit confidence metadata and fallback behavior. Separate geocode resolution from business filtering. Use viewport-based queries with debouncing to prevent excessive calls. Keep map and list under one canonical state to avoid divergence. If tile or route services fail, degrade gracefully to list-only mode with clear messaging.

Use stable place IDs internally and avoid relying on display names as keys. Mark stale geocoding results and include recency timestamps for trust.

Minimal concrete example

marker payload:
{ place_id:"plc_91", lat:30.2672, lng:-97.7431, confidence:0.86, last_verified:"2026-02-11T19:00:00Z" }

3. Project Specification

3.1 What You Will Build

A map widget with synchronized list, filters, and route estimate panel.

3.2 Functional Requirements

  1. Query points in current viewport.
  2. Render clustered markers and synchronized sidebar.
  3. Show location details and route estimate on selection.
  4. Provide fallback list-only mode on map failures.

3.3 Real World Outcome

User searches "EV chargers near downtown Austin".
Widget shows map with clustered markers and synced list.
User selects location -> details card + ETA appears.

4. Solution Architecture

viewport events -> geospatial query tool -> result envelope -> map renderer + sidebar reducer

5. Implementation Guide

5.1 The Core Question You’re Answering

“How do I keep location experiences usable when geospatial data is uncertain or unavailable?”

5.2 Concepts You Must Understand First

  1. Geocode confidence scoring.
  2. Viewport query debouncing.
  3. Fallback UX principles.

5.3 Questions to Guide Your Design

  1. What confidence threshold triggers warning labels?
  2. How will map/list state stay canonical?
  3. What happens when route provider is unavailable?

5.4 Thinking Exercise

Design a fallback matrix for provider failures: map tiles down, route API down, geocoder timeout.

5.5 The Interview Questions They’ll Ask

  1. How do you prevent map call storms during pan/zoom?
  2. How do you represent geocode uncertainty?
  3. How do you test map/list synchronization?
  4. What are key geospatial edge cases?
  5. How do you degrade gracefully?

5.6 Hints in Layers

  • Hint 1: Implement list-only mode first.
  • Hint 2: Add map integration as enhancement.
  • Hint 3: Keep one canonical selected-place state.
  • Hint 4: Add provider health banners.

5.7 Books That Will Help

Topic Book Chapter
Data resilience “The Pragmatic Programmer” Pragmatic architecture sections
Defensive design “Code Complete” Robustness chapters
API boundaries “Clean Architecture” Interface boundaries

6. Testing Strategy

  • Viewport query debounce tests.
  • Map/list selection synchronization tests.
  • Provider outage fallback tests.

7. Common Pitfalls & Debugging

Pitfall Symptom Solution
Divergent state stores Marker and list mismatch Single canonical state source
Missing debouncing API over-call and lag Add viewport debounce
No fallback mode Empty unusable widget Provide list-only degraded state

8. Extensions & Challenges

  • Add geofence alerts.
  • Add multi-stop route optimization.
  • Add historical movement playback.

9. Real-World Connections

  • Fleet tracking
  • Field service dispatch
  • Store locator apps

10. Resources

  • OpenAI UI and state-management docs
  • Geospatial API provider docs

11. Self-Assessment Checklist

  • I can explain confidence handling for geospatial data.
  • I can keep map/list interactions synchronized.
  • I can ship a graceful fallback mode.

12. Submission / Completion Criteria

Minimum Viable Completion

  • Synchronized map/list with location details.

Full Completion

  • Includes provider-failure fallback and confidence-aware messaging.