ContextCapture can produce 3D meshes and orthophotos.For a large project tiling is required to circumvent hardware limitations and enable cluster processing.The orthophoto production can also be divided into several parts, to limit the size of each individual file.
Please note that the orthophoto partition does not follow the reconstruction tiling. It has its own tiling mechanism as described below.However, adjusting the settings properly allows you to use the same tiling for both your reconstruction and orthophotos.
For a given reconstruction, the outward boundaries that will be considered are:- The automatic rectangular bounding box that includes the whole scene. The X and Y axis of this bounding box are in accordance with the orthophoto production spatial reference system- A manual bounding box determined with custom values or a KML polygon (again adjusted on the X and Y axis of the production spatial reference system)
The orthophoto tiling starts from the bottom left corner of the bounding box and increments from left to right (part_1_1, part_1_2, part_1_X, etc.) and bottom to top (part_1_1, Part_2_1, Part_X_1, etc.).The ortho parts are squared. The size of the tiling depends on two parameters: The maximum image part dimension and the sampling distance.The sampling distance is the size of a pixel in your orthophotos.The maximum image part dimension is the number of pixels of your ortho part.The size, in meters, of your orthophoto part is “Max image part dimension” x “sampling distance”.For example, with a sampling distance of 5 cm/pixel and a max image part dimension of 4000 pixels, the ortho parts will be 200m x 200m.
Note that the parts at the right and bottom edges of the bounding box are clipped to the bounding box extent.
It is possible to make the orthophoto parts and reconstruction tiling fit together perfectly.To achieve this: - The reconstruction tiling spatial reference system and the orthophoto production spatial reference system should be the same.- The bottom left corner of your ortho bounding box must corresponds exactly to the top left corner of one of the tiles in your reconstruction tiling (exporting the tiling in KML format can be useful to work with and help to define the bounding box: right click on the reconstruction -> export tiling to KML).- Max image part dimension x sampling distance must be equal to the reconstruction tiling tile size.