Original Post Date: November 2010
In today's world of sharing data, there's a tremendous need to be able to reproject data to accommodate different coordinate systems. The following text outlines the steps needed when dealing with images.
Note that the following content is based on MicroStation V8i SS2, but is also applicable to the previous release.
Let's suppose that you have a suite of old design files that were drawn correctly in the UTM projection. Perhaps these files came from MicroStation V7 which didn't have the concept of assigning a coordinate system to a file. You may also have corresponding images that are in the, now obsolete HMR format that are also in a UTM projection. When attached, the images line up just fine to the vector graphics. Since all the files fit together nicely there really isn't a need to have, or even worry about a coordinate system.
Note that in the graphic below, the map is leaning towards the left since it's up against the right side of the zone edge and lies near 53 degrees latitude in the northern hemisphere.
In this example, let's suppose that there's a requirement to deliver or publish the data in a latitude/longitude projection.
One of the first things to do is assign a coordinate system to the design file. To do that, navigate to Tools > Geographic > Select Geographic Coordinate System and choose the correct system for the file. In this example, I've selected UTM83-11 as noted in the graphic below. For additional information on how to do this, please refer to the following article:
The next step is to convert the HMR file to the iTIFF format. An iTIFF file is smaller and faster to work with and is based on the industry TIFF standard. You can do this conversion from the Raster Manager > File > Save As dialog. Be sure to click on the Options button and note the available settings. The end result will be iTIFF image knows that it has a named coordinate system of UTM83-11. After all, it inherited this information during the conversion process.
Here we have the same vector file, but have assigned and reprojected the graphics to the Latitude/Longitude NAD83 geographic coordinate system as shown below. You can see that the graphics are flattened and wider than in the UTM projection above.
Obviously when the iTIFF image is attached, it won't lie over the reprojected graphics (LL83) since it has an entirely different coordinate system (UTM83-11). The coordinate system of the attached image can be seen if you turn on the Coordinate System column in the Raster Manager.
The graphic below shows the vector graphics in one view and the attached image another. Note the physical differences between the two.
To overcome the apparent mis-match in coordinate systems, simply perform an on-the-fly reprojection to the image. To do that, go to the Raster Manager and enable the display of the Inherit GeoCS from Model column.
Note the new column and tick mark to indicate that the image is inheriting it's coordinate system from the model which places it way off in space somewhere.
By simply turning this option off, the image uses it's own coordinate system and automatically reprojected to fit the coordinate system of the active file. Note that this reprojection is for display and printing purposes only; the original image is still in the UTM83-11 projection. This is a wonderful example of how MicroStation can automatically reproject data as long as it understands the geographic location of your design.
Finally, you can choose inherit or not inherit the coordinate system when you initially attach the image. Just drill into the Geometry pane of the Raster Attachment Options dialog as shown.
This tutorial was produced with MicroStation V8i SS2 and did not require the use of add-on software or applications.