Michael The OS Grid Ref is another way of representing British National Grid (i.e 0,0 off the SW of Isles of Scilly). The OS have a grid (based on a dim and distant operational requirement to allot work) which breaks the country into square eg SJ in your example. The numbers appended to the two characters represent the offset from the point of origin of that square. The more numbers the greater the precision, eg can be accurate between 10km (4 figure grid ref SJ49) and 1m (12 figure grid ref eg SJ480596908765). Or on to higher levels of precision but I don't know if this is actually done.
eg 1. Origin for tile SJ is 300000, 300000. 2. Get the accuracy by splitting the suffix to get the offset from 300000,300000. 3. 8 figs (incl the letters SJ) give you accuracy to 100m - 480 * 100 for x, 908 * 100 for y. 4. Hence 300000 + 48000 x, 300000 + 90800 y 5. 348000, 390800 = SJ480908. You can't - as far as I know - do this directly in MapInfo so you'll need some automation if you're doing lots of gridrefs. I've put a VB class on Directionsmag.com (CoordinateConverter.cls) which does this conversion both ways - the algorithm is pretty self explanatory but the trick is knowing the origin for each grid square. Its on the OS site - or just nick my code. The class also does UTM to LL for the UK (based on Airey 1830) - starting vals are properties and can be set for other systems - all based on an OS algorithm that they implemented in an Excel spreadsheet on their site - which is fine for doing one at a time! Paul Crisp Syntegra Innovation Place Delta Bank Road Newcastle NE11 9DJ Tel 0191 461 4522 Fax 0191 460 1987 -----Original Message----- From: CLARK, Michael [mailto:[EMAIL PROTECTED]] Sent: 02 August 2002 14:31 To: '[EMAIL PROTECTED]' Subject: MI-L Grid References and Mapinfo How do you plot an grid reference (e.g. SJ480908) onto a base map in Mapinfo. Do you need to translate the GR into cartesian coordinates first? If so, how do I do that. Thanks Dr. Michael Clark --------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 2355 ******************************************************************** This email may contain information which is privileged or confidential. If you are not the intended recipient of this email, please notify the sender immediately and delete it without reading, copying, storing, forwarding or disclosing its contents to any other person Thank you Check us out at http://www.syntegra.com ********************************************************************
