Hi Ross I appreciate your answer and hope that my over simplistic approach can be of some value to Sarah.
I am a techie by nature and perhaps sometimes over complicate things. Your suggested applications surely would have some constraints though? Wind and slope would mean a more complex approach for disaster planning. I would think more often than not gas leaks blow in one predominate direction as might spills unless on a very level site. Perhaps because I'm based in Wales mountains spring to mind as meaning simple expansion would not always be suitable for telecommunications. If you increased signal strength by a percentage you could still have blind spots and these could fall within the buffer in the simplistic solution.( Having said that I'm always impressed that across the Alps our European colleagues give us five bar signal strength on our mobiles while most routes from my home have no coverage! How do they do that??). However I can see for your suggested applications you would need to start somewhere and as I say I hope the proposed buffer has some value as a starting point to a solution. Regards Bob Quoting "Bagwell, Ross" <[EMAIL PROTECTED]>: > Bob, > > The application that Sarah asked about would be very applicable in > situations such as disaster planning (spill sites, contamination areas, > etc) > and telecommunications (uniform gain in the strength of a tower signal or > broadcast area), just to think of a few. > > -Ross E. Bagwell > GIS Manager > Universal Access Inc > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > Sent: Thursday, January 15, 2004 12:26 PM > To: Hooper Sarah > Cc: '[EMAIL PROTECTED]' > Subject: Re: MI-L Poly size increase > > > Hi Sarah > > To answer your question well it would certainly help to know why the area > of > > the polygon needs to grow by a value and indeed what the polygon > represents. > > I have listed below one technical solution but before that I would just > like > to > show some caution by suggesting for most applications this would be a > dangerous > assumption. > > If a planning authority decided to allow a 10 per cent growth in housing it > is > highly unlikely they would allow a uniform growth. There would be many > constraints. Physical constraints such as rail, river and road and > environmental considerations would make the following a meaningless > solution. > The growth is just as likely to be a bubble on the side of the existing > area > as > a uniform growth as detailed below. > > > With that reservation in mind:- > > One solution... > > Find the existing area by one of MapInfos alternatives ... eg using select > tool > select object. > > In a similar way find the perimeter of the object. Multiply the area by the > > percentage increase to get the increased area. > > Divide the increased area by the perimter to find a buffer value. > > Buffer the object with the offset as calculated. > > This solution to be very accurate would need to be iterative. The new > object > > would not exactly be the correct new area because on obtuse angles around > the > perimeter it will increase too much and on acute by not enough. However if > say > you wanted to increase by 10% and your first calculation for the offset is > say > 9.2 metres and this gives a real increase of 11% your second iterative > solution > for the offset would be 9.2m x 10/11. ( hope this makes sense ). > > This technical solution is of course based on increasing the object out > from > > its centre uniformly by a constant buffer size and I cannot straight off > think > of an application where this would be apporopriate! > > Regards > > > Bob > > > > > > Quoting Hooper Sarah <[EMAIL PROTECTED]>: > > > Hi, > > > > I am trying to increase polygon sizes by a percentage value. How do I go > > about this? And is there a way to increase many at once? > > > > Thanks in advance, > > Sarah > > > > > > > > > > > **************************************************************************** > **** > *** > > The contents of the e-mail and any transmitted files are confidential and > > intended solely for the use of the individual or entity to whom they are > > addressed. Transport for London hereby exclude any warranty and any > liability > > as to the quality or accuracy of the contents of this email and any > attached > > transmitted files. If you are not the intended recipient be advised that > you > > have received this email in error and that any use, dissemination, > > forwarding, printing or copying of this email is strictly prohibited. > > > > If you have received this email in error please notify > > [EMAIL PROTECTED] > > > > This footnote also confirms that this email message has been swept for > the > > presence of computer viruses. > > > **************************************************************************** > **** > *** > > > > > > --------------------------------------------------------------------- > > List hosting provided by Directions Magazine | www.directionsmag.com | > > To unsubscribe, e-mail: [EMAIL PROTECTED] > > For additional commands, e-mail: [EMAIL PROTECTED] > > Message number: 9923 > > > > > > > > > --------------------------------------------------------------------- > List hosting provided by Directions Magazine | www.directionsmag.com | > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > Message number: 9927 > > > This communication contains information from Universal Access, Inc. (or its > affiliates) which is confidential and may also be privileged. It is for > the > exclusive use of the intended recipient(s). If you are not the intended > recipient(s), please note that any distribution, copying or use of this > communication or the information in it is strictly prohibited. If you have > received this communication in error, please notify the sender immediately > and then destroy any copies of it. > > > --------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 9935
