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Digimap is an online map and data delivery service, available by subscription to UK Higher and Further Education establishments. Operated by EDINA at the University of Edinburgh, Digimap offers a number of data collections, including Ordnance Survey, historical, geological, aerial photography, LiDAR, marine maps, land cover mapping, global mapping and census data. For more information about Digimap go to our website: https://digimap.edina.ac.uk Background image Contains OS data (c) Crown Copyright and database right 2022
The MasterMap data in Digimap’s MasterMap Download has undergone its April update; the new data has a currency date of January 12th 2011. The data is available to download for new orders, re-orders of previous data, and as a Change-only Update (CoU) which provides only the changes to the data since it was downloaded.
CoU and Re-orders can be accessed from the Your Account page in MasterMap Download; simply select the order you want to refresh and use the CoU or Re-order (current data) buttons below the order list.
Please note that the OS MasterMap raster data (Tiff files) in Digimap’s Data Download are only updated once a year in September. You can read about these maps in a previous blog post here: MasterMap Background Maps
VectorMap District Beta Release
VectorMap District data has now been updated from the alpha release to beta in Data Download. You can read about the differences in a previous blog post here: VectorMap District beta release
The currency dates for all the different data products in Digimap’s Ordnance Survey Collection can be found on the following help page: Dates of Updates to Digimap
Check the date on which you created the original Order. If you created it after the last set of CoU was released but before the next set of CoU is released, then you already have the latest version of the data. If a release of CoU is imminent, you should wait until after the release date, and then check your data order for the availability of CoU.
I have downloaded CoU for my area, but having applied it to my existing data holding, nothing looks different. Why is this?
Not every feature changes every time a Change-only Update is released. It may be that none of the features in your data holding have been updated this time. It is not possible for EDINA to determine exactly whose orders contain changed features.
You may also find that there are some small changes to the attributes for your data. These are harder to identify if you are simply looking for changes visible on a map. It isn’t necessarily the geometry or position of a feature which has changed. When you plot the changes on a map, you may not see them, because the changes may relate to data in the attribue table.
Why can’t I have CoU for other datasets?
Only OS MasterMap data offers Change-only Update. This is because other datasets are not structured in a way which enables CoU to be identified and extracted separately. Other datasets are also not updated so frequently.
The next release of Change-only Update data for OS MasterMap will be put into service on Tuesday 24 March 2009. The currency date of the new data will be 20 January 2009.*
Change-only Update (CoU) applies only to the OS MasterMap data. It does not apply to any other data product.
EDINA collates all the data changes released by Ordnance Survey over a 6-month period, and makes these available through Digimap approximately every 6 months. The previous update was released in September 2008.
What is the point of Change-only Update?
Change-only Updates enable you to update your data holding without needing to store multiple copies or versions of the same data. By taking only the changes to the data you hold you can minimise the storage requirements for your data, while still maintaining an up-to-date dataset. This is particularly useful if you are studying changes to an area over time.
Most users will not need Change-only Update. CoU is only useful to you if you already have a full copy of the original data to which you can apply the changes.
How do I download CoU?
You can download Change-only Updates only for data orders you have already submitted within Digimap’s Mastermap Download facility. Go to the Your Account page within Mastermap Download and scroll down to the table of Orders.
You will see a list of all your previous Orders, and in the final column you will see whether or not CoU is available for that Order.
If CoU is available, click the radio button in the far left column for the Order you require. Below this table, you will see two buttons in a blue box:
Click the first button to Order Change-only Update. The data file will be delivered in the usual way: you will receive one email to say your Order has been received and is being processed, and a second email to say your data is ready for collection.
If you submit a new order for OS MasterMap data, by defining the Layer, Themes and your chosen area, you will automatically receive the latest version of the data; this will include all the latest changes. Change-only Update will therefore not be available for such an Order until the next batch of CoU is released.
Example
You submit an Order for data on 20 March 2009. In the Orders table under Your Account, the Order details say that CoU is not available. This is because you already have the latest version of the data.
If you submit a second Order for data on 27 March 2009, you will also see that the order details say that CoU is not available. Again, you have the latest version of the data; it includes the changes which were released on 24 March.
If you go back to look at your first Order (submitted on 20 March) on 2 April 2009, you will see that COU is now vailable for this Order. This is because the changes released on 24 March are now available; they were not available when you submitted the original order.
* Although the latest update is dated 20 January 2009, it takes time for Ordnance Survey to process and release these data, to send them out to EDINA and for EDINA to process and load the data into the database. This accounts for the time delay between the “freeze date” of the database (20 January 2009) and the release date (24 March 2009).
