A surface is a triangulated mesh that can have georeferenced images draped over it or can be coloured according to the heightfield. Most commonly, a surface will be defined by:
- Elevation Surface: Ground elevation with air photos, geophysical images etc draped on top. The surface may also be coloured according to elevation.
- Placed Image: A manually georeferenced image at an arbitrary position in space (eg. a section image placed vertically in the scene or a scanned map of old mine workings).
All surfaces use a tiling and paging system that allows images and heightfields of any size and resolution to be used in a fast and efficient way. To ensure efficient access, Spatial Integration will automatically generate overviews of large images and grids if they are not already available. The overviews are in an industry standard format so that you will also get improved performance in other geospatial software such as QGIS. Overviews will have the same name as the original file with a .ovr extension appended. Don’t worry if you delete your overview file, a new one will be generated next time you use it. Note that overview files are not included in Packages, because they add size and will be automatically generated when the package is opened anyway.
Don’t be afraid to throw large images at Spatial Integration. We regularly use a single grid containing SRTM data of the entire globe. This is a single-band GeoTIFF image with tiling and embedded overviews coming in at 162GB.
Spatial Integration will constantly load new data as you pan around the scene and zoom into areas with more detailed data. Multiple areas are loaded simultaneously from different parts of your hard drive. You will therefore get much better performance from solid-state hard drives than spinning disks.