This was sent to me, presumably by mistake.
> -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Brad Nesom > Sent: Wednesday, 28 September 2011 4:29 p.m. > To: Alister Hood > Subject: Re: [Qgis-user] RE: [Qgis-community-team] Problem changing a > shapefile's coordinates > > my suggestion is load each file seperately by itself. find a location in the > file tha tis at least close to the same point for each.note the coordinates of > the project. > if all the files are in fact lat lon (4326) the values should be like 35, 98. > or 35, -98 > if they are 100k size there is a good chance they are UTM, > 1million probably stateplane. > The prj file is what determines how the gis projects the shape file. the > coordinates don't change. > if there is no prj file the software will probably default it to 42326 while in > fact the values are for a completely different system. > if you insert the unknown with a known and they line up then you know what > system the coords are in. > So using the on the fly projection you can fool the system into telling you > what system it is in. > > file a, b, c, and d > a =4326 > b=unk > c=utm > > by adding 1 file first you will know what the prj says it is. then add another > to see if it lines up. > you are trying to find the unk then you can get rid of the prj ifor the unk > file. > with on the fly DISABLED 2 files with the same prj should line up (if they > don't they aren't the same projection) no matter what the prj says. > use 2 known files to verify with on the fly (a,c) > use 1 planar file with unk (zoom to extents to see scale and direction from > known) > make some informed guesses and convert file d to several possibilities > use each posssiblity by itself (this will set the crs ) then add the unk with > on the fly > when you find one that lines up with unk (mystery solved) now saveas and the > prj will be correct > > This is rather tedious but it works for identifying incorrectly projected, > unprojected, incorrectly identified projections. > > > > On Tue, Sep 27, 2011 at 4:30 PM, Alister Hood <[email protected]> > wrote: > > > Hi, > > > -----Original Message----- > > From: [email protected] > [mailto:qgis-community-team- > > [email protected]] On Behalf Of giannis Nj > > Sent: Tuesday, 27 September 2011 10:53 p.m. > > To: [email protected]; [email protected] > > Subject: [Qgis-community-team] Problem changing a shapefile's > coordinates > > > > > Hello, > > > > I have a .tiff file and a .shp one, showing the same area in the map > but they > > come in different coordinates. From the Properties of these files I > give them > > the same projection (4326 - WGS84), same as the project properties, > but still > > they don't match. Actually, the coordinates of the shapefile remain > the same > > (different from the project's), something that I thought would change > by > > changing the CRS. > > > Like Micha said, assigning a different CRS to a layer does not change > the coordinates of features in the layer, it just tells QGIS which CRS > the coordinates are in, for the sake of 'on the fly' CRS transformation. > For a layer to show up in the correct place you must assign it the > correct CRS (if not already assigned), and either: > (1) enable 'on the fly' CRS transformation, or > (2) save copy of the layer, transformed into the same CRS as the > project, as the other guys have described, and use that copy. > > (1) is fine if you only need to display the layer. If you need to do > some sort of spatial analysis using layers in different CRSs you > normally need to do (2), because many tools in QGIS require layers to be > in the same CRS. > > > > I guess it's not that simple to change the coordinates in a > > file, so i would like to ask how it is possible to manage this so that > the two > > files will come in the same coordinates. Is something in the settings > that i > > forget to do? Is this able in QGIS or i have to try on another GIS > program? > > > > Thank you. > > > Regards, > Alister _______________________________________________ Qgis-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-user
