Imagery Dissection

Imagery can often be very large and images may need to be broken into sub-images to enhance the speed of systems delivering imagery to end users.  A small study was undertaken to determine whether Landgate should be delivering imagery in smaller mosaics. 

As a result of an action item arising from a WALIS council meeting, WALIS undertook an online survey (distributed to all WALIS Councillors and WALIS Council Liaison in June 2006) to ascertain firstly, how widespread the practise of imagery dissection was, and secondly, if there was common ground in terms of size requirements.

17 responses were received. Key points to come out of the survey were:

• The main reason for imagery dissection is one of file size
• Images are redistributed to field officers requiring smaller images
• Images are dissected to individual requirements – both in terms of geography and size

The survey showed that there was a significant variation in customer requirements and there was no real common ground between the agencies. Had this survey revealed that more customers required images dissected to a common pattern, it is possible that a cost-effective business case could be developed for Landgate to defray the extra extraction costs on to the relevant agencies for user-specific dissection work. Landgate have previously provided CALM (now DEC) with an inclusive quote for implementing business processes in-house at Landgate to extract images dissected specifically to DEC’s needs, though this has not been pursued.

If sufficient agencies can compromise upon an acceptable dissection pattern, investigation of a semi-automated process to suitably dissect image data (eg to 50 thou sheets) could be worthwhile. This would be cost effective, however, only if the dissection was sought over common geographic areas, and that issues of storage, archiving, distribution etc were resolved.

If you have any further comments, please contact the WALIS office at walis@walis.wa.gov.au or on 9273-7046.