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In Imagery Layer, what do you mean by 'seamless imagery'?

The imagery in OS MasterMap® Imagery Layer is seamless in that it is colour balanced and edgematched. This ensures that analysis of information across image boundaries is not seriously hampered by misalignment or inconsistency.

Variations because of time of day differences (for example, lengthening shadows, colour changes), time of year differences (for example, vegetation changes, river levels) and age differences (for example, new developments, and road changes) mean that some variation is inevitable and an overzealous attempt at imposing an artificial evenness would be misleading.

Great care is taken to ensure that imagery is 'stitched' together in a seamless manner to avoid distortion to features, such as buildings.  We collect imagery in strips with a generous overlap between each photograph. We then use seamlines to select the centre of each image, taking care to cut them along natural boundaries and at right angles to roads. 

The same principles are used to place new imagery updates into the layer. As the imagery is supplied by 1km x 1km tiles, these can contain more than one date of imagery. The date flown on the metadata will always be the oldest imagery present in the tile, however this is usually only a small percentage of the actual content.

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