Surfaces

A surface is a 3D mesh that can have georeferenced images draped over it, or be coloured by its height. Surfaces come in three kinds:

1. Elevation Surface: ground elevation with air photos, geophysics images and other overlays draped on top. It can also be coloured by elevation.
2. Placed Image: an image you georeference by hand and place anywhere in space, such as a cross-section placed vertically in the scene or a scanned plan of old mine workings.
3. SEGY Seismic Section: a 2D seismic line shown as a vertical curtain coloured by amplitude.

Images on a surface can come from files on your computer, from streaming image servers, or live from QGIS through the QGIS Live Map.

Large grids and images

Surfaces can use grids and images of any size and resolution, loading only the detail needed for what is on screen. Don't be afraid to give Spatial Integration large files: we regularly use a single 162 GB GeoTIFF of SRTM elevation for the entire globe.

To read large files quickly, Spatial Integration needs overviews (reduced-resolution copies of the file). If a large grid or image has none, they are built automatically the first time it is used. Overviews are written in an industry-standard format with the same name as the original file plus .ovr, so other software such as QGIS benefits from them too. If you delete an overview file, a new one is built the next time it is needed. Overviews are not included in packages, because they add size and are rebuilt when the package is opened.

Spatial Integration loads new data constantly as you pan and zoom into areas with more detail, so it runs much better from a solid-state drive than from a spinning disk.