Depending on the photo count, and especially the processing quality selected, DataHub outputs such as the orthomosaic may be large in terms of file size. Larger-sized files can sometimes be inconvenient to use or load in some GIS applications.
This article shows a quick workaround on how to compress/ resize the orthomosaic using QGIS.
1. If you haven't already, download QGIS from their website. For the purposes of this guide, we are using QGIS for Windows.
See website: https://qgis.org/en/site/forusers/download.html
2. Open QGIS on your computer.
3. Import your raster by going to Layer>Add Layer>Add Raster Layer or simply click and drag your orthomosaic.tif file into the QGIS workspace.
4. Once the tif file has been loaded into QGIS, pan to the Layers pane at the lower left portion of your screen. Right-click on your ortho layer, click Export and Save as...
5. You will be presented with the Save Raster Layer as customization menu where you can specify your output file name, compression values, and other options.
6. Click Rendered Image. Name your output tif file. In this case, we named it Exampleortho_compressed. Go to Resolution and from the previous values in the Horizontal and Vertical fields, edit the values to suit your compression purposes. In this case, we will enter 0.5x0.5. You can change these values further depending on your goal file size. Click OK.
- The horizontal and vertical resolution values should be the same.
- A smaller value will return a bigger file size. For example, a 0.05x0.05 resolution file will be bigger in size than a 0.5x0.5 resolution file.
7. Depending on the file size of your original tif file, the processing time may take several seconds to a couple of minutes. When done, QGIS will display the compressed file in the workspace as well as in the layers pane.
8. For accuracy, you can disable and enable the layer visibility to see if the tif files match up. You can also confirm the file sizes by checking the details of your files in the folder directory.
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