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Mastermap Styling

Thu, 05 Oct 2006

With EDINA preparing OS Mastermap data for general distribution as part of Digimap, one of my colleagues has become an early adopter for trialling purposes. Whilst I have come across Mastermap in various guises, this was the first time I had seen the whole processing side up close. My colleague downloaded a couple of layers for a 5x5km area which came to over 200Mb. The first problem was loading it in to ArcMap which is one of the least standards compliant GIS packages around (although this might well be coming in v9.2). A trip over to ESRI UK and a download of MapManager 9 allowed the conversion of the OS GML into a geodatabase. Mastermap then loaded fine, although with default ESRI symbolisation. A lot of digging and we finally came across a style file that symbolises the Mastermap data in the same fashion as the default OS styling (and pleasant enough it is too). Its worth noting that you can get a free OS Mastermap GML Viewer from Snowflake Software.

We then downloaded all layers (although no imagery) for a 5x5km area and, 2-hours later, MapManager produced a 750Mb geodatabase. Hmmm, some planning ahead me-thinks. This is clearly a big headache for EDINA (it took about 6-hours for the data request to be processed, rather than the 2-3 minutes for LandLine), hence the need for testing!

Guy McGarva wrote at 2006-11-09 17:23:

Hi Mike, Ken I just wanted to respond to some of the issues raised - sorry it's taken so long to respond, but I've not been following this blog until recently.
I just wanted to make you aware that the web site that we have set up at http://www.edina.ac.uk/mastermap/index.shtml has a number of resources available, including instructions on how to load the data into ArcGIS and also a set of sample styling files at http://www.edina.ac.uk/mastermap/resources/GISresources.shtml that I've just updated and put in a more obvious place. There is also information for some other systems and links to various software tools. If you know of any others please let us know so we can add them to the list.
Also, I have just extracted a 25km2 area of London in about 8mins and from our records it looks like this is how long the processing took for your job at this end. It could be that the apparent delay has been caused by a delay in the email notification process. Just to check, please try the job again, and if you don't get an email in about 10min go the Your Account page and check on the job.
The size of the database sounds about right, however, as in tests it looks like the Geodatabase size is only slightly smaller than the uncompressed GML file, which for the 25km2 area of London (Topo Layer) that I extracted was about 35Mb gzipped and 800Mb uncompressed. This created a Geodatabase of about 500Mb. See http://edina.ac.uk/mastermap/resources/docs/MMcomparison.pdf for more comparisons.

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