[Qgis-user] Problem changing a shapefile's coordinates

[Brad Nesom]

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.

2011/9/27 giannis Nj <netsagief at hotmail.com>

>  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. 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.
>
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