MOSAIC OBLIQUE

Orthorectified-oblique mosaics offer a continuous projected image from an oblique perspective, which Blom are able to offer from four angles; north, south, east and west.

The orthorectified oblique images are projected and ortho-rectified to correct the distortion of the terrain and represent true ground position as closely as possible with current technology. This creates a product that is not only easy to manipulate, but can also overlap with vector data whilst still offering the visualisation of the building fronts.

All the images are available in WGS84 Spherical Mercator (EPSG:3785) projection. Orthorectified oblique imagery can be overlapped with vector data as easily as traditional orthophotos. However, they have some drawbacks compared with the natural oblique images: 

• The ortho-rectifying process can distort the imagery and make the objects appear stretched For example areas containing large elevation differences, such as tall buildings and bridges, may appear warped due to the rectifying process following the terrain model
• The imagery is not suitable for vertical measurements.
• When creating the continuous ortho mosaic with this imagery, seam lines can be noticeable in the join of the different images used. This can lead to some artefacts like buildings appearing inclined in two different directions.

In general, real oblique images offer better quality, however the flexibility of ortho rectified mosaic imagery may be a decisive factor in certain applications.