File layout

Each ortho projection image is shipped with the following file layout:

<file-name>.png image file.
<file-name>.yaml orthographic projection parameter file.
<file-name>.offset geographic coordinates offset file.
<file-name>.ply dense point cloud used to compute the orthographic.

Orthographic projection parameter file

Here is an example of orthographic projection parameter file:

res: 0.040000000000000001
inv_res: 25
num_rows: 4672
num_cols: 11475
px_offset: [1002, 968]

bounding_box:
  x_min: -40.048606872558594
  x_max: 418.982666015625
  y_min: -38.701129913330078
  y_max: 148.1962890625

Parameter	Description	Unit
`res`	Image resolution : size in meters of each pixel	m
`inv_res`	Inverse of image resolution	1/m
`num_rows`	Number of rows of the image	pixels
`num_cols`	Number of columns of the image	pixels
`px_offset`	Offset that should be applied to the points integer coordinate to obtain image coordinates.	pixels
`bounding_box`	Bounding box of the input point cloud (not needed for projection calculations)	m

Geographic coordinates offset file

Here is an example of geographic coordinates offset file:

311800 5391300 0

The coordinates of the points in the PLY point cloud are local. To obtain the global coordinates (the ones in the Coordinate Reference System (CRS) of the map), one should add geo_offset to each point. This is file contains the (x, y, z) coordinates of geo_offset.

World to pixels

1. Cartesian global (ENU) → Cartesian local

Cartesian global (ENU): This is cartesian ENU coordinates as defined by the Coordinate Reference System (CRS) (for example WGS84 / UTM zone 33N).

Cartesian local: This is the cartesian reference coordiantes of the PLY point cloud.