projection info of dgn map

[gisuser]

hi,
the projection info lies in the dgn file or shown on the map.
can anybody help me in this matter.

thanks in advamce.

[Gede2A]

you mean that you know the projection of the dgn file?
If so choose the same for your project (settings/project properties) and for your layer (right clic, properties/general/specify crs).

[gisuser]

hi,
i mean the projection info is in the map file but in proprietory format and not readable.
i am interested in mapping the x,y with known long/lat values.
as this is a vector layer,how should i geo reference it.

can anybody help me.

thanks in advance.

[best]

hi,
i mean the projection info is in the map file but in proprietory format and not readable.
i am interested in mapping the x,y with known long/lat values.
as this is a vector layer,how should i geo reference it.

Hi gisuser,
I doubt that the projection info is in the file. What is possible is, that the data are projected. This means they have some x/y coordinates corresponding to a certain projection. You have to know which projection this is, then you can tell QGIS to use this particular projection. However in CAD it is not unusual to draw data just somewhere into the plain with coordinates normally starting at 0/0. If this is the case, QGIS can, of course, visualize the data but as they are not linked to any place on earth you cannot use them with GIS data being linked to a certain place (projected or not).
So check your dgn-data what coordinates they have. Are these coordinates somehow similar to the other data you use in the part of the world you focus on?

hope this helps

best

[gisuser]

hi,
The text on the map when displayed shows the upper left corner as 78.0,18.0 and bottom right as 79.0,17.0.
Now projection info not known.it is map of hyderabad/india.
i want it to be georeferenced as any raster file.
The above points should be mapped to x,y of dgn map.
is their any possibility of such with vector maps.

And is it possible to change extents of vector file like gdal_translate does for raster files.
please help.

thanks in advance

[Gede2A]

the advantage of vectors is that you can reproject them easily if you know the projection and whatever the projection you work with by choosing it in a menu. You cannot reproject like a raster, by hand.
In your case, if you have not defined in qgis a projection, the default one is wgs84.
But because you have a result, the data is been correctly read. I can see in google earth that this is lat long coordinates in wgs 84. So just "change" the projection in the one you want, i.e. the same as your rasters, and that's it

[best]

had this almost finished when Gede2A was faster

hi,
The text on the map when displayed shows the upper left corner as 78.0,18.0 and bottom right as 79.0,17.0.
Now projection info not known.it is map of hyderabad/india.

This seems to be the location of Hyderabad in lon/lat. What projection is your raster data? Use this projection as your QGIS project's projection and activate on-the-fly-projection. In the Options dialog check Prompt for CRS (see section 8.2 of the User Guide for Version 1.1). When loading the dgn I would give it a try with WGS84 (EPSG 4326). See if that maps the dgn with your raster data.

i want it to be georeferenced as any raster file.
The above points should be mapped to x,y of dgn map.
is their any possibility of such with vector maps.

And is it possible to change extents of vector file like gdal_translate does for raster files.

Be sure that you know the difference between raster and vector data (see the User Guide). The extent of vector data is defined by the data themselves.

[gisuser]

hi,
I see the lat/long data is displayed as a info on map, not that the QGIS Coordinate Capture is translating and showing.
i don't know the projection,nor the parameters.only thing i know the lat/long of upper left and bottom right corners.
as per my understanding, the points of map should get mapped to known lat/long.
if i am correct how it should be done.

i am asking for all this, because other tools like ArcGIS package is georeferencing the same dgn file.
but how it is able to.

please help

[gisuser]

hi,

added to my previous post, i like to share (not that nobody knows, what is know i am just conveying) how transformation is done using simple ascii file as world file.
in arcgis tools, this world file along with dgn file would help the dgn get georefernced.
is something like this available in open source.

please help

[best]

hi,
I see the lat/long data is displayed as a info on map, not that the QGIS Coordinate Capture is translating and showing.
i don't know the projection,nor the parameters.only thing i know the lat/long of upper left and bottom right corners.
as per my understanding, the points of map should get mapped to known lat/long.
if i am correct how it should be done.

i am asking for all this, because other tools like ArcGIS package is georeferencing the same dgn file.
but how it is able to.

please help

Have you tried what has been proposed as a solution? Did it work or not?

hi,

added to my previous post, i like to share (not that nobody knows, what is know i am just conveying) how transformation is done using simple ascii file as world file.
in arcgis tools, this world file along with dgn file would help the dgn get georefernced.
is something like this available in open source.

please help

Be sure that you know the difference between raster and vector data (see the User Guide). World files are for raster data. see e.g. http://en.wikipedia.org/wiki/World_file

best