5,000 changes a day and other urban myths..

We all know the statistic that 80% of all information is spatial, but I guess like most people I’m not clear where that particular figure has come from, and thinking about it.. I not convinced it is actually true. There is much information held in databases around the world which is about activities which happen at specific locations, but as much as 80% ?

Another much repeated statistic is that Ordnance Survey makes 5000 changes to the national geospatial database every day – this time however, although I’m not sure where the statistic came from, I can put more accurate figures in place.

As part of the development of a new Oracle Spatial database system, we have looked at the number of transactions going through the database in order to scale the system, a 10 node RAC cluster by the way ..

In general day to day operations the OS actually makes between 30-50,000 changes per day, representing the modification of existing features in the database and the addition of new features into the landscape, things like new housing estates.

Over the past few years however a larger than average amount of change has been happening as a result of the Positional Accuracy Improvement Programme, resulting in peaks of 500,000 changes in a day !!

These figures sound a lot especially compared to the often stated 5,000 changes a day, but you need to remember the database contains around a billion individual features.

We really did need a new database !!!

Written and submitted from home, using my home 802.11 network.

10 comments

  1. Rob

    Ed,

    Another figure I often hear is the OS have 70,000 topology rules they use when buildingmanaging MasterMap? Myth or fact?

    Rob

  2. Vector One

    I agree with you about the 80% spatial information item. It is likely lower but who knows how these things get calculated.

    500,000 changes per day! You folks are busy.

    That works out to 500000/ 1700 OS employee’s or so = 294 changes per person

    Assuming a 7 hour day with an hour for lunch then,
    294 changes / (6 h X 60min) = 0.81

    You folks are hard workers, putting out almost one change every minute of the day for every employee.

    I often thought your original claim of 5000 was low. You need to sell me more on the 500000 though. 😉

    Does this mean non-OS employee’s are also making changes to the national databases?

    Interesting numbers Ed.

  3. Muki Haklay

    Ed,

    The most important figure is how many real-world changes of the geometry or significant attribute (such as change in functionality of a building). So is the number 50,000 represent total transactions with Oracle which will include all kind of other bits of information, or is it the number of changes of geometry objects?

    Muki

  4. Ed

    Hi Muki,

    Most do represent geometry attribute changes, which are the main reason any other attribute would change. Some to do with Postal Address changes are those where more of the transactions would be to non-geometry attributes.

    ed

  5. Mark Probert

    Ed – I thought it was 5,000 house units?

    Also – does this mean the oft quoted 430 million features is way out of date? I could do with knowing because I oft quote it!

  6. Ed

    Mark,

    Good to hear from you..

    I could imagine that could be the case, but nobody understands what a house unit is outside a few people at OS, and database transactions are pretty transparent.

    ed

  7. Philip Round

    Mea culpa! I had a hand in the 5000-changes-a-day figure when I worked in the Press Office at OS. Former Director General David Rhind wanted a way of demonstrating to the general public just how much change was going on in the British landscape, and what a big task OS had in keeping maps and data as up-to-date as possible. Ian Logan (former Director of Data Collection) and I looked at all sorts of mind-boggling data input figures and eventually settled on house units of change (as being the nearest thing a non-technical punter would understand – everyone can imagine what “a house” is). However, we thought the annual figure was still beyond comprehension, so we averaged it out to a daily total and rounded it down slightly to get the 5000 figure. That was about nine years ago; not sure that anyone has looked at it since.

    Philip Round (now living in Canada and desparately missing the sort of detailed walking maps for which OS is rightly renowned!)

  8. Ed

    Hi Phillip,

    Great to see the application of organisational memory.. So i think we have now cleared thing up…

    5,000 house units changes represent 30-50,000 actual geometry changes in the database.

    Thank you !!!

    ed

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