Using the Ordnance Survey Maps API with OCAD
Ordnance Survey provides Premium Plan subscribers with the first £1,000 of Premium Data free each month. This guide explains how to set up and use the OS Maps API in OCAD to download map data.
Setting Up the OS Maps API
- Create an Account: Sign up for an account at OS Data Hub.
- Create a New Project:
- Navigate to Data > API Projects in the OS Data Hub.
- Click to create a new project, accept the terms, and name the project (e.g., OS Maps).
- Add OS Maps API:
- Click Add API, search for OS Maps API, and add it to your project.
- Scroll to find the WMTS API Endpoint address and click Copy.
- Configure OCAD:
- Open OCAD and load the map project you want to add data to.
- Go to Background Map > WMS / WMTS in the toolbar.
- Select Add and open the Edit WMS/WMTS Properties dialog.
- Set the service type to WMTS and enter a descriptive name (e.g., OS Maps Service) for easy reference later.
- Paste the copied WMTS API Endpoint address into the URL field.
- Save the settings. The service is now stored in OCAD for future use.
Note: You can close the OS Data Hub after saving. Monitor your data usage via the OS Data Hub dashboard if you use the API frequently.
Downloading Map Data in OCAD
- Zoom to the Desired Area:
- Zoom into the map area you want to download, ensuring it fills the OCAD window.
- For large areas, consider downloading in smaller sections to manage file sizes.
- Connect to the WMTS Service:
- Go to Background Map > WMS / WMTS and select the WMTS service you added (e.g., OS Maps Service).
- Click Connect to view available layers.
- Select a Layer:
- Available layers include OS MasterMap (layers 1–5, different color palettes) and OS Leisure 1:25/50k (layer 6).
- Choose a layer labeled with 27700 (e.g., 4 Road_27700 for road-focused maps).
- Configure Download Settings:
- Check Add user-defined extent of selected layers to background maps (offline).
- Next to Offline Directory, select the folder where your map project is stored and create a new subfolder for OS background maps.
- Set the resolution:
- For OS Leisure 1:25/50k (layer 6), use a resolution of 2m or higher.
- For OS MasterMap layers, use 0.25m which is sufficient for tracing for sprint maps. For very fine lines, you can increase the resolution to 0.125m, but note this requires downloading more tiles from OS, resulting in larger file sizes.
- Click Set extent to current view to update the coordinates to match the visible area.
- Download the Data:
- Click Add to start the download.
- Monitor the download progress in the bottom-left corner of the OCAD window.
Note on File Types: Downloaded background maps are saved in PNG format, accompanied by a corresponding .pgw file containing georeferencing information. Keep these files together in the same folder to ensure they open correctly in OCAD.