KGA Data Managementផ្ទាំងអន្តរកម្ម
Imagery Downloader
ទាញយករូបភាពផែនទីតាមអ៊ីនធឺណិតសម្រាប់តំបន់មួយ ផ្គុំជារូបភាពតែមួយដែលមានកូអរដោនេ រួចបន្ថែមទៅក្នុងផែនទី។
- រកឃើញនៅឯណា
- Processing ▸ Toolbox ▸ KGA Toolbox ▸ KGA Data Management ▸ Imagery Downloader
- លេខសម្គាល់ algorithm
- kga:imagery_downloader
- ប្រភេទឧបករណ៍
- Interactive dialog — modeless, needs the QGIS window and an internet connection
ទិដ្ឋភាពទូទៅ
Downloads web-map raster tiles for an area, stitches them into one georeferenced image, saves it in the chosen format and CRS, and adds it to the map below the vector layers. The source list is data-driven; the only source shipped is Google Satellite.
Tiles are fetched through QGIS's network stack — proxy and authentication honoured — by a background task with a thread pool, retries with back-off and automatic slowing down when the server throttles. Tiles are written into a sparse tiled GeoTIFF work file as they arrive, and a checkpoint records which are done, so an interrupted job resumes from the same folder without re-downloading anything.
ប៉ារ៉ាម៉ែត្រ
| ផ្ទាំងគ្រប់គ្រង | ប្រភេទ | តម្លៃលំនាំដើម | ការពិពណ៌នា |
|---|---|---|---|
| Imagery source | Combo box | Google Satellite | Entry from the source registry. |
| Download extent | Combo box | Map canvas | Map canvas, layer extent, a box drawn on the map, or a polygon layer — the bounding box is downloaded and pixels outside are masked. Selected features only is optional. |
| Zoom level | Combo box | Auto | Within the source's min–max zoom; the ground resolution at the area's latitude is shown. Auto matches the canvas scale. |
| Output CRS | CRS selector | Project CRS | EPSG:3857 is pixel-exact; others are reprojected with bilinear resampling. |
| Format | Combo box | GeoTIFF | GeoTIFF, JPEG, PNG, JPEG 2000, ECW — only those the local GDAL can write. |
| Build pyramids | Boolean | — | Internal overviews for GeoTIFF. |
| Transparent outside polygon | Boolean | — | Clip mode: transparent where the format has alpha, otherwise white. |
| Connections | Number 1–16 | — | How many tiles are fetched in parallel. |
| Output folder / File name | Folder + text | — | Where the result and, if enabled, the checkpoint go. |
| Enable checkpoint | Boolean | on | Keep <name>.kga_checkpoint.json and <name>_work.tif so a stopped job can resume. |
របៀបប្រើ
- Open KGA Data Management > Imagery Downloader, or press its button on the KGA toolbar.
- Choose the imagery source and set the Download extent.
- Pick a Zoom level — read the ground resolution it reports before committing.
- Set the output CRS, format, folder and file name.
- Press download and leave it running. If it is interrupted, start it again with the same folder and file name and it carries on.
លទ្ធផល
- The finished image, georeferenced — embedded for GeoTIFF, JPEG 2000 and ECW; a world file (
.jgw/.pgw),.prjand.aux.xmlfor JPEG and PNG. - The layer added to the project with the source attribution in its metadata.
- The work file and checkpoint removed after a successful export.
កំណត់សម្គាល់ និងដែនកំណត់
- Google's terms restrict bulk downloading and offline use of map tiles. The tool's Help text says so and the result layer carries Google's attribution, but the window does not stop to ask for an acknowledgement before it downloads. The user is responsible for having the right to use the imagery.
- Extents crossing the antimeridian are rejected. Latitudes are clamped to ±85.0511°. Above 5,000,000 tiles, Download is disabled.
- JPEG is limited to 65,500 px per side and has no alpha, so empty areas come out white.
- ECW is offered only when GDAL has an ECW writer with an encode licence key — see Raster Format Converter for the same caveat.
- The work file needs about 3 bytes per pixel of the tile mosaic in free disk space, on top of the final image.