Or you could change the SQL statement to take a unit as well: Select CartesianArea(Overlap(PolygonTable1.Obj, PolygonTable2.Obj), "hectare") , PolygonTable1.ID, PolygonTable2.ID >From PolygonTable1, PolygonTable2 Where PolygonTable1.Obj Intersects PolygonTable2.Obj Into a Noselect
This also gives you the possibility to specify whether you want to use CartesionArea(obj, "area unit") or SpericalArea(obj, "area unit") HTH, Peter Horsb�ll M�ller GIS Developer Geographical Information & IT COWI A/S Odensevej 95 DK-5260 Odense S. Denmark Tel +45 6311 4900 Direct +45 6311 4908 Mob +45 5156 1045 Fax +45 6311 4949 E-mail [EMAIL PROTECTED] http://www.cowi.dk/gis -----Original Message----- From: Dan Bowles [mailto:[EMAIL PROTECTED] Sent: Wednesday, November 17, 2004 5:53 AM To: S�ren Breddam Cc: MapInfo-L Subject: RE: MI-L FW: Determining polygon areas and proportions within polygons Hi Soren You sent me this email some time ago on area and proportionoverlap commands, at the time I used other means, however, I'm now using areaoverlap to calculate areas of lots affected by flood constraints. It's working quite beautifully, however, I'm struggling with the area units. Changing the map units from the Map>Options menu item does not seem to change the output units. Is there some way I can modify the command to set units to "hectare"? You're help is greatly appreciated. Regards Dan Bowles BSc GIS Officer Harper Somers O'Sullivan PO Box 428 HAMILTON NSW 2303 E [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> T 02 4961 6500 M 04 3834 8372 -----Original Message----- From: S�ren Breddam [mailto:[EMAIL PROTECTED] Sent: Thursday, 12 August 2004 5:13 PM To: 'Dan Bowles' Subject: SV: MI-L FW: Determining polygon areas and proportions within polygons Hi Dan, You do have options doing this with SQL: MB help: AreaOverlap( ) funtion: Purpose Returns the area resulting from the overlap of two closed objects. Syntax: AreaOverlap ( object1, object2 ) object1 and object2 are closed objects. Return Value A Float value representing the area (in MapBasic's current area units - use Set Area Units... to change this) of the overlap of the two objects. Example: Select AreaOverlap(PolygonTable1.Obj, PolygonTable2.Obj) , PolygonTable1.ID, PolygonTable2.ID Received: From PolygonTable1, PolygonTable2 Where PolygonTable1.Obj Intersects PolygonTable2.Obj Into a Noselect Browse * From a ProportionOverlap( ) function: Purpose Returns a number that indicates what percentage of one object is covered by another object. Syntax ProportionOverlap(object1,object2) object1 is the bottom object (not text or points) object2 is the top object (not text or points) Return Value A Float value equal to Area(Overlap(object1,object2) ) / Area(object1). HTH S�ren Breddam -----Oprindelig meddelelse----- Fra: Dan Bowles [mailto:[EMAIL PROTECTED] Sendt: 12. august 2004 02:14 Til: MapInfo-L Emne: MI-L FW: Determining polygon areas and proportions within polygons Sorry, original message didn't work with explanatory attachment. Hope you understand without... -----Original Message----- From: Dan Bowles [mailto:[EMAIL PROTECTED] Sent: Thursday, 12 August 2004 9:35 AM To: MapInfo-L Subject: Determining polygon areas and proportions within polygons Hi all I have a very large data set of vegetation classifications (various coloured polygons in the base of the example map attached), in a GIS also including proposed vegetation corridors (blue polygons), national parks (green polygons) and state forests (brown polygons). The veg corridors, NPs and SFs do not intersect, however, the vegetation classification polygons intersect across all other layers. I need to determine how much area there is of each vegetation class in total and how much area of each class is contained within each of a number of distinct veg corridors (blue), and generally within NPs (green) and SFs (brown). I also need to determine percentages of each veg class within NPs, SFs and veg corridors compared to the entire area. I am having trouble getting MapInfo to automatically generate these statistics for me, any advice you could give would be fantastic. Thanks for your help Dan Bowles --------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 14089
