Satellite Imagery Download
Overview
Downloads tiles within a specified extent from an online map tile service, mosaics them automatically into one raster image, and outputs a GeoTIFF (.tif).
The tool is suitable for quickly obtaining basemap imagery for map display, background comparison, and preliminary analysis. The output is an RGB three-band raster.
Use Cases
- Basemap archiving and offline use: Convert online imagery or vector basemaps to local rasters for offline viewing and sharing.
- Project comparison and inspection: Download imagery for a project area as a background for comparison with existing data.
- Quick map production: Download a basemap at an appropriate zoom level for a specified extent and output it as GeoTIFF.
Parameters
| Parameter | Description | Notes |
|---|---|---|
| Data source | Selects the imagery or basemap source and layer type. | Available data sources and layer types depend on platform configuration. Common options include Tianditu vector, imagery, and terrain layers. |
| Extent | Specifies the download extent. | You can enter [min_x, min_y, max_x, max_y] directly, select the view extent, or use a layer extent. Coordinates use the current map project or view coordinate system. |
| Zoom level | Tile zoom level. | Valid values are 1-18. Higher levels provide more detail but require more tiles and longer processing time. Test with a small extent or lower level first. |
| Output raster file | Output GeoTIFF file path. | .tif is recommended. The output is an RGB raster image. |
Data Notes (Tianditu)
When Data source is set to Tianditu, the tool downloads basemap tiles through the Tianditu WMTS tile service and mosaics them.
- Service type: OGC WMTS (
GetTile). - Tile coordinate system: The tool uses Tianditu
TileMatrixSet = w, corresponding to Web Mercator (EPSG:3857). - Output type: Whether you choose vector, imagery, or terrain, the output is a rendered RGB raster, not vector features.
Tianditu Layer Types
The following table describes common Tianditu layer types in the tool. In the interface, these are usually shown as layer type or data type options. “With labels” means a label layer is overlaid on the basemap.
| Layer type in the interface | Content | Label behavior |
|---|---|---|
| Vector basemap (without labels) | Rendered Tianditu vector basemap, including roads, administrative divisions, and water systems. | No labels are overlaid. |
| Vector basemap (with labels) | Vector basemap plus vector labels. | Overlays labels such as place names and roads. |
| Imagery basemap (without labels) | Rendered Tianditu remote sensing imagery basemap. | No labels are overlaid. |
| Imagery basemap (with labels) | Imagery basemap plus imagery labels. | Overlays labels for map production and positioning. |
| Terrain hillshade | Tianditu terrain hillshade basemap. | The current implementation overlays terrain labels by default, such as contours or place names. |
| Global boundaries | Tianditu global boundary layer, such as national boundaries. | This layer usually has a transparent background. Transparent areas are composited with a white background in the GeoTIFF output. |
For map display, use Imagery basemap (without labels) as the background and overlay Imagery basemap (with labels) or other label and road layers as needed. For thematic maps, use Vector basemap (without labels) to avoid text interference.
Steps
- Start the tool: Open Geoprocessing Toolbox > Data Management Tools > Data Download, then start Satellite Imagery Download.
- Select a data source: In Data source, select the required imagery or basemap type.
- Set the extent: Select the view extent or a layer extent, and manually adjust the bounds if needed.
- Set the zoom level: Choose a zoom level based on the target detail and area size.
- Configure the output: Set the save location and file name for Output raster file.
- Run the task: Click Run and view progress in Task List. After completion, load the output and inspect it.
Notes
- Extent and zoom level strongly affect processing time: Tile count grows quickly as the extent and zoom level increase. Split the area or lower the zoom level when needed.
- Network and service availability: The tool depends on online services. Network instability or service rate limits may cause failures or missing tiles.
- Data usage and compliance: Use online basemap data according to the source service terms. It is recommended for internal comparison and auxiliary analysis only.