Dr Mike J Smith
Kingston University

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Trouble and strife with OS data

Thu, 21 Jan 2010

I recently had a map submitted to the Journal of Maps that made good use of Mastermap data. Although not an extensive amount was used, it is primarily based upon it so I suggested he check out the JISC-OS license with particular reference to my post on what this means for PDF based maps. He has described his experiences:

Trouble and strife with OS data

My map was created using terrain analysis of a Digital Elevation Model generated from airborne LiDAR data. In order to provide some context to the main feature of my map I used Ordnance Survey Mastermap data for features such as roads, railways, rivers and general land use. On reviewing my map the editor at the Journal of Maps suggested I should check whether the use of this data falls within the current OS licensing agreement. I discovered that my map was in breach of this agreement on a number of levels. Not only did my map include prohibited vector data, but the total number of pixels per image was over double that of the maximum set by OS at 1,048,576. I went through the pain staking process of trying to reduce the overall size of the images in my map so that they fell within the agreement terms, but the effect of rasterising the vector data resulted in a severe impact on the overall quality of the layers. It was at this point I decided it would be best not to use any OS data in my map.

Instead, I created my own layers by digitising the most important features (major road and rail routes, urban areas, and rivers) from airborne imagery collected for the study site. In this instance I was fortunate to have this data available, as other sources of imagery, such as Google Earth, are liable to have poor spatial accuracy. One vector layer which I could not digitise using the airborne imagery was an outline of the UK, used to identify the location of the study site. To overcome this I downloaded a UK coastline line shapefile from Open Street Map (available at Cloudmade). In fact the data available here also includes road and administrative boundary features that may be useful to other users.

The lessons learnt here are that the restrictions imposed by OS effectively make their data unusable in map making for publication.

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Gary wrote at 2010-01-22 11:31:

This looks more like the chap was using inappropriate data for the scale needed rather than a licensing issue. "In order to provide some context to the main feature of my map I used Ordnance Survey Mastermap data for features such as roads, railways, rivers and general land use.." - surely OS Mastermap has way too much detail for providing just "some context".

Mike Smith wrote at 2010-01-22 11:43:

Its a good point and not made clear in the text. Yes, Mastermap would not necessarily be the best choice for a regional map putting the site in context. However what he didn't say was that the map covers in detail a 500m stretch of a transport corridor and needs detailed outlines of road, rail and rivers. Mastermap is ideal for this purpose but cannot be published "as is".

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