Jul 222013

As part of ongoing efforts to improve the usability of data delivered by Digimap, we have made some significant enhancements to one of the Ordnance Survey licensed datasets.

OS VectorMap® Local is a relatively new product from Ordnance Survey providing slightly less detail than OS MasterMap but still very useful for detailed backdrop mapping. Individual buildings are shown as well as roads, rivers, landcover and contours. The vector version of the data is provided by Ordnance Survey in GML 2.1.2. This is a standard geospatial data format developed by the Open Geospatial Consortium; however it generally needs to be converted into a proprietary format before being used in GIS and CAD software.

To make using this data easier we are now providing OS VectorMap Local in both Shapefile and DWG formats. Shapefiles can be easily opened in ArcGIS and most other GIS programs including OpenSource GIS software such as QGIS and gvSIG. DWG is the native format for AutoCAD and can be used in many other CAD systems as well.

This data is now available for download from the Data Download application in the Digimap Ordnance Survey Collection. VectorMap Local is in the Vector Data section; to change the format of the data you are downloading click on the Change link under Options once you have added it to the basket.

Digimap Data Download Basket

Click image to view full size.

Creating the data:

TO achieve the best results when recreating the data in different formats we had to use different software products for different formats. To convert the data to Shapefile we used the OpenSource Software GDAL program called “ogr2ogr” and for the DWG conversion we used FME from Safe Software. The image below shows part of the FME Workbench project used to convert the data to DWG.

Image showing FME Workbench converting GML to DWG

Click image to view full size.

1: Shapefiles

To convert the GML to Shapefile we created a lookup table between the Feature Codes in the GML data to Shapefile Layers.  As Ordnance Survey do not provide any guidance in their User Guide as to how to group features in VML , we analysed the data and experimented with various groupings, so that in the end we split the data into a possible 22 separate Layers. These layers may contain multiple feature classes but as they all have the original feature codes on them as attributes as well as all the other original attribution, further distinction between features can be achieved for representation and querying.

Example of the Shapefile data in ArcMap:

Image of VML in ArcMap

Click image to view full size.

A simple set of Layer Files has been created for use in ArcMap and can be downloaded from the VML Help page.

2. DWG

To convert the data to DWG we had to go through a similar process (as well as our data team becoming much more familiar with AutoCAD). We originally intended to produce DXF format data but this turned out to be a problem. We had to make some decisions about how to store attribution in the output data and one of the main considerations was the size of the resultant files. To begin with when we converted a tile of VML that was 60Mb of GML, it expanded in size to 240Mb when converted to DXF containing attributes as Inserts. This was unusable in systems we tried so we had to work on ways of making the files smaller. The first thing we did was change the format from DXF to DWG. As both formats are commonly read by various CAD systems this seems a reasonable thing to do although it may make the data slightly less interoperable. This changed the file size to 44Mb for our sample dataset. This was still quite large and some systems were having problems with this, especially when dealing with tiles in dense urban areas. We therefore decided to change the way we were storing attributes in the data. Instead of using Inserts we used Extended Entity Data (or XData) which was one of the options available in FME. This stores a fixed amount of information against an entity in the drawing. We use this to store the attribute information that was in the original GML data, including the original feature code. It’s a bit more difficult to work with this data but it can be viewed in AutoCAD  Map 3D by using the Express Tools –> Tools –> List Object Xdata or typing xdlist in the command prompt.

Using XData brought the size of our sample tile down to 10Mb and was usable in all the systems we tested it with. If you need access to the attributes either as Inserts or as Map 3D Object data please let us know.

As part of the conversion process we defined the representation for features in the DWG file, including point symbols and area fills. Features have also been grouped together into separate Layers as we did with the Shapefiles.

Example of the data in AutoCAD:

Image showing VML in DWG in AutoCAD

Click image to view full size.

Finally, after getting the project set up in FME and a thorough testing of the data, we ran the batch process to convert the data. This took nearly 3 days per format to convert the full load of our national coverage of VML data. This data will be updated on the normal update schedule, as we get updated VML from Ordnance Survey as Change Only Updates so future conversions will be much quicker.

Remember,both these datasets are available through Data Download by selecting VectorMap Local and then changing the format after you have added the data to your basket.

We intend to produce alternative formats for other products, including OS MasterMap, so we would very much like to hear your thoughts on the data that we have produced so far and let us know if this meets your needs.




May 252012

The VectorMap Local (VML) data in the New Data Download service has been updated, it is now current as of April 2012.VML Standard View from Digimap RoamVML data is currently only available to download in GML format as supplied by Ordnance  Survey. However you can download a free converter from Rolta which will convert the GML to Shapefiles or MapInfo TAB files. There is guidance on where to get the converter and some pointer on how to use it on the following help page:

Guidance Notes for OS VectorMap Local

VectorMap Local in Digimap Roam

Processing the data for Digimap Roam takes a little longer than making it available for Download, but we hope to have it into service in the not too distant future. Remember that if you want to see VML data in Roam you have to zoom in to the Street View and use the alternative representations to change from the 1:10 000 Raster data to one of the four different VML styles.

Full instructions on how to view VML data in Digimap Roam   can be found in this video:

YouTube Preview Image


 May 25, 2012  Posted by at 11:24 am Data Changes & Additions Tagged with: ,  No Responses »
Jul 012011

The VectorMap Local (VML) maps mentioned in the previous blog posts are now working in Digimap Roam. There is a video on YouTube showing you how to view all the different mapping styles that are now available at the four most zoomed in levels; including all the VML maps and Land-Line style MasterMap:

YouTube Preview Image

For more informations see the previous blog post here:

More Improvements Coming Soon, June 20th 2011

Jun 202011

We have had another very busy month and so a new batch of improvements for the Digimap services will be coming soon.

Printing in Ancient Roam

At the moment downloading data or saving screen images are the only ways to use the maps available in Historic Digimap once you have logged out.  Soon you will be able to create and save high quality PDF maps from Ancient Roam for use offline. We hope you will find this a much better way to get the best quality mapping out of the service.

Ancient Roam PDF

A sample image of what a PDF from Ancient Roam may look like.

New Data in Digimap Roam

Since the arrival of the Ordnance Survey’s latest large scale product, VectorMap Local,  we have been busy thinking of the best way to include it in the Digimap Roam. We have decided to use it to create four new representations available at two different scale levels.

Here is a quick look at what the four different representations might look like:

VML standard

Vectormap Local- Standard

VML Streetview

Vectormap Local - Streetview

VML Plan

Vectormap Local - Plan

VML Raster10k

Vectormap Local - 1:10,000 Raster

We haven’t stopped there either; we are also going to add in Line Drawing style mapping to the two most zoomed in levels; for those who like their MasterMap plain and simple, similar to planning application maps.

MasterMap - Plan

MasterMap - Line Drawing

You will be able to select the different views from the Map Content Control Tab using a drop down list.Alternate representations choice Menu

For more information about VectorMap Local look in the Digimap help pages as it is already available for download:

OS Products: OS VectorMap Local

Annotation Tools in Geology Roam

For those of you who have tried the annotation tools in Digimap Roam it will come as no surprise that we are very pleased to announce that we are now working on adding the same functionality in Geology Roam. Again the annotation tools are a first draft and will have exactly the same functionality as Digimap Roam’s tools.

Geology Annotation Tools

Once they are released we’d really like to hear from you about which functions you use and what else you would like added. We are already hoping to add in some Geology Mapping symbols for you to add to the maps.

As an added bonus we are also putting in the measurement tools so you can measure areas and distances too, so you can tell how long a fault is or what area is covered by different rock types.