This procedure can be followed to convert and reproject a DGN file that has a Latitude/Longitude Geographica Coordinate System (GCS) to a DGN with a Northing/Easting GCS. The complication in this process is the change in the storage units of Degrees to Distance. Unless the exact sequence of steps in this process are followed the results will be erroneous. For example, the converted drawing could have Northing and Easting working units with Degrees as the units. Or, have the correct working units but not reproject to the correct location. Another dangerous outcome, easily overlooked, is the Working Units and projection may be correct but the coordinates in the drawing are not correct for the projection.
There is a condensed General Procedure version of this process near the bottom.
The process followed here starts with a MicroStation DGN file of New York State that has LL84 as the GCS with working units of Degrees. LL84 is a Lat/Long GCS and is valid anywhere on earth. SkaneatelesLk.dgn was created from the New York State drawing using the Copy Fence Contents to File tool. LL84 was then assigned as the GCS for SkaneatelesLk.dgn. Of course both have identical working units of Lat/Long in Degrees and when attached, align perfectly. SkaneatelesLk.dgn is the example file converted and reprojected to State Plane GCS of NY83-CF and uses Survey Feet and Survey Inches for working units.
After the conversion is complete the SkaneatelesLk.dgn can be attached as a reference file, using the Reprojected Orientation (as shown below), to any DGN having the LL84 or other valid Lat/Long GCS.
The CORRECT Procedure is described below followed by some variataions as WRONG procedures with the erroneous results described.
CORRECT Procedure:
- From the menu: Settings > Design File. In the Design File Settings dialog, select the Working Units category. NOTE: The master units are Degrees with a resolution of 10,000 per Degree.
- In the Advanced Settings click the Edit button and OK the Alert box with the warning.
- Change the Unit Type from Angular (Lattitude/Longitude) as shown below to: Distance as shown in the next image below.
- Leave the 10,000 as is and select Survey Feet, which is the distance unit for State Plane GCSs.
NOTE: the working area is 170,591,236 miles for each axis.
5. Click OK to complete the change from angular to Survey Feet working units as shown below.
6. Click OK to close the Design File Settings dialog.
With the Working Units set to match the future GCS, the new GCS can be assigned.
7. From the MicroStation Tools menu select Geographic > Select Geographic Coordinate System.
Use the From Library tool to assign a new GCS. In this example, an appropriate selection is 1983 North American Datum State Plane Central Zone US Foot. In MicroStation US Foot equals Survey Foot.
8. Select the Library tab, Library folder > Projected (Northing Easting) > North America > United States of America > New York. Scroll down and select NY83 - CF...
9. Click OK to assign the selected GCS.
The Geographic Coordinate Syastem Changed dialog displays. Select the Reproject the data to the new Geographic Coordinate System option as shown below and click OK.
By selecting the option to reproject the data, all elements are reprojected to new coordinates and the process is complete.
The Geographic Coordinate System dialog now reflects the new GCS as shown below.
This is as far as you need to read. But, if you have done this process in the past but differently, you may compare the results below to your results.
General Procedure: Convert a DGN from Lat/Long to Northing/Easting
- From the menu: Settings > Design File. In the Design File Settings dialog, select the Working Units category. NOTE: The master units are Degrees with a resolution of 10,000 per Degree.
- In the Advanced Settings click the Edit button and OK the Alert box with the warning. Change the Unit Type from Angular (Lattitude/Longitude) as shown below to: Distance. Leave the 10,000 as is and select Survey Feet, or other distance unit used in the target GCS.
- Click OK to complete the change from angular to distance units.
-
Click OK to close the Design File Settings dialog.
-
From the MicroStation menu, select: Tools > Select Geographic Coordinate System. Assign the target Northing/Easting, or other linear GCS selecting the "Reproject the data...." option.
Wrong Procedure: Same except change the resolution.
- From the menu: Settings > Design File. In the Design File Settings dialog, select the Working Units category.
- Change the Unit Type from Angular (Lattitude/Longitude) as shown below to: Distance.
- Change the resolution from 10,000 to 1,000 and select Survey Feet, which is the distance unit for State Plane GCSs.
- Assign the NY83-CF GCS with the option to reproject the data.
Result: When the converted DGN is attached using the Reprojected, or any other, Orientation - it is in the wrong place and is at the wrong scale.
Wrong Procedure: Reproject before changing the storage units from Angular to Distance.
- Assign the NY83-CF GCS with the option to reproject the data.
- NOTE: at this point when attached to the New York State drawing, it will be properly alligned using the coincident orientation but the working units are Degrees.
- Change the working units to Distance using Survey Foot and Do Not change the resolution.
Result: It will attach in the correct location and scale. It all appears to be correct. Problem is the coordinates are not correct for the given GCS AND it cannot be attached using the Reprojected orientation.
Also See:
Design File Precision with a Latitude Longitude Projection