In a previous article "Geo Hound: A Tool to Automatically Fetch Website Map Service Addresses", I introduced the powerful Geo Hound tool. Follow-up articles like "Get Hidden Government Map Data in 2 Steps (Geo Hound + Wuhan One Map)" and "Shanghai One Map Data (Trial)" shared practical experiences. Many readers subsequently asked: Can this map data be downloaded for offline use? While various methods exist, I'll share my two most-used approaches.

Method 1: Using QGIS (Recommended for Compatible Services)

This is my go-to method. Using Wuhan One Map as an example (Note: As of publication, direct access via QGIS has been disabled by Wuhan authorities. Replace with other sources. This guide is for educational purposes only. Do not download or disseminate confidential data):

  1. Open QGIS and load the Wuhan One Map service (obtained via Geo Hound).
  2. Right-click the layer > Export > Save As....

  3. Critical Settings:

    • Uncheck Create VRT
    • Set desired output resolution.
  4. Click OK. Exporting large areas takes significant time.
  5. Result: A local raster file (~400 MB in this example). Select an appropriate area to avoid excessive file sizes.

Method 2: Manual Tiling + Vectorization (The "Fallback" Method)

This universal approach works for almost any web-accessible map. Let's use Shenzhen One Map (https://pnr.sz.gov.cn/d-xgmap/) as an example (Geo Hound can identify this source, but direct QGIS loading may fail).

Principle: Data viewable in a web browser can be captured, though effort varies with required resolution.

Simplest Approach (Low Res):

  1. Visit the map service.
  2. Open browser developer console (Chrome recommended). Remove distracting elements/layers.

  3. Capture the cleaned map view:

    • Option A: Basic screenshot.
    • Option B (Better): Select the map node in Elements inspector. Press Ctrl+Shift+P (Win/Linux) or Cmd+Shift+P (Mac). Search for and run Capture node screenshot.

Higher Effort Approach (Higher Res):

  1. Use browser tools (e.g., Network tab) to capture all individual map tiles (*.png/*.jpg).
  2. Assemble tiles manually using software like GIMP or Photoshop (like a puzzle).

Georeference the Image:
Import the stitched image into QGIS. Use Layer > Georeferencer to assign real-world coordinates.

Conclusion

  • Use dedicated map downloaders where possible. They're efficient.
  • Method 1 (QGIS Export) is best for compatible services, but avoid massive datasets.
  • Method 2 is a proof-of-concept fallback for difficult cases. It's less recommended due to high effort and potential quality issues.
  • CRITICAL: Do not use these methods to download copyrighted, proprietary, or confidential data! Always prioritize legal data acquisition channels.

What methods do YOU use? Share in the comments!