I have a project that involves porting a lot of information from ordnance survey to a spatial database. From that database I'm going to extract the information I need for a routing application. However, I have a problem as I'm not sure how no turn works.

I have trawled through the ordnance survey documentation but haven't been able to work out how no turn in the environment qualifiers apply. My question is, from the data in ordnance survey, how do you find out which links you can't turn onto (from link x)?

Any help would be appreciated.


Are you using the OS ITN data with RRI? (Road Restriction Information)

osrdlk - The road links with all restriction info as attributes
osrdlk_mandturn - A turn feature class for mandatory turns
osrdlk_noentry - A turn feature class for no entries
osrdlk_noturn - A turn feature class for no turns


(the OS ITN Open forum might be of help to you - http://www.ordnancesurvey.co.uk/itnforum/index.jspa)

The best way to create ROAD networks is using ESRI (UK) Productivity Suite and load in the ITN data to Oracle via SDE (or File Geodatabase)


  • Hi, I believe the data I am using is the OS OpenData using Road Route Information and Road Link Information to find stuff like one way, no turn etc. – Manatherin Jan 21 '11 at 9:04
  • You need the PAID OS MasterMap ITN DAta with RRI (they ['OS'] will not give away that information for free') – Mapperz Jan 21 '11 at 15:13
  • Vector District? or Meridian2? - There are some major issues with both in respect to routing. – Mapperz Jan 21 '11 at 15:17
  • Hi, Sorry it took me so long to reply, I had to confirm what OS data I was using, the data is the paid OS MasterMap Data – Manatherin Jan 25 '11 at 12:44
  • ITN comes in two formats - you need RRI data included to make turns in a network. – Mapperz Jan 25 '11 at 17:41

After further confusion I emailed the Ordnance Survey for further information. The Directed Links are order dependent so for single no turn it would be you can't turn from first link whilst travelling with/against the direction of digitising on the first link (based on orientation) into second link going with/against the direction of digitising on the second link (based on orientation)


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