Hello Stephen, Just a quick note to Bob's comprehensive reply, there is one other danger of changing coordsys bounds. If you have two tables where there is some sort of node topology going on (let's say you snapped nodes from objects in one table to nodes in another), after changing the coordsys bounds, there is no guarantee that they will match exactly any more.
Regards, Warren Vick Europa Technologies Ltd. http://www.europa-tech.com Tel: +44 20 8398 3955 x201 -----Original Message----- From: bob young [mailto:[EMAIL PROTECTED]] Sent: Wednesday, August 07, 2002 4:20 PM To: Stephen Dew Cc: [EMAIL PROTECTED] Subject: Re: MI-L Coord Sys Boundary Hi Stephen MapInfo stores coordinates as an integer ( long integer ) number of steps multiplied by a step size. It has one step size for X and another step size for Y. If you make the boundaries smaller you reduce the step size. If you make the width equal the height your step sizes become the same. There are exactly 2,000,000,000 steps so if you set limits for example to 0,0 to 2000,2000 km then your step size becomes exactly one millimeter. In the UK the whole country fits nicely into 2000 km square so By Designs translators use the above boundary to achieve 1 mm accuracy in mapping Ordnance Survey data. Without specifiying this boundary there would be an error of +- 4.1225 mm on X coordinates and an error of +- 4.9985 mm on Y coordinates ( ie using MapInfo BNG WITHOUT MBR) . Bottom line is to make it small where you can. However an exact multiple of a base unit might be better than using the absolute smallest value you could get away with. For example in an imperial system it might be worth making it a quarter of an inch rather than 59/240 ths of an inch. Regards Bob Young By Design www.mapsbydesign.co.uk (0044) 1633 881117 In message <[EMAIL PROTECTED] .com>, Stephen Dew <[EMAIL PROTECTED]> writes >We inherited several files that have Coord Sys Boundaries that are riduculously >big (94,100 miles square, not square miles). > >Does anybody know the MapInfo implications of having the coordinates so far >outside the useful area of a projection, in this case that is US State Plane. >y > >--------------------------------------------------------------------- >List hosting provided by Directions Magazine | www.directionsmag.com | >To unsubscribe, e-mail: [EMAIL PROTECTED] >For additional commands, e-mail: [EMAIL PROTECTED] >Message number: 2421 > --------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 2425 --------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 2452
