How To Change Drawing Units In Civil 3d

Point Coordinate Transformations (CAD Clinic: Civil 3D Tutorial)

30 November, 2008

By: Phillip Zimmerman

Use Bespeak File Formats to import and export points to assigned coordinate systems.

Editor's Annotation: This tutorial courtesy of Imaginit.

Reading external ASCII files through a Point File Format creates cogo_points. Civil 3D has several pre-defined file formats. When using a Bespeak File Format, it assumes the coordinate system or local coordinates match between file and drawing. However, there are times when the file and the drawing take different coordinates systems, i.due east. NAD27 coordinates in the file and NAD83 for the drawing'due south coordinate organisation. If the file and cartoon's coordinate systems differ and yous want to transform the coordinates on import, and then the Point File Format must have an assigned coordinate arrangement. A coordinate organisation is assigned in the file-format definition panel'south centre left. Run across Effigy 1.

A file format with a coordinate system.

The second place coordinate transforms can occur when importing points directly into a surface. The bespeak files process is exactly the aforementioned as importing points from an ASCII file to the cartoon, only the resulting points do not become cogo_points, rather they get surface points.

The last place where betoken coordinate transformations may occur is when inserting survey points into a drawing. If the survey and drawing take different systems, the point coordinates transform when inserting them into the cartoon. Also, when a survey's units are U.S. survey foot and the drawing uses international feet, when inserting the survey points into the drawing, a transformation occurs. Defining a Point File Format with a Coordinate System There are two places to ascertain a Point File Format. The first is the Setting panel'southward Signal branch, and equally the second is a modification or copy of a format in the Import/Export Points dialog box.

When in the Import/Export dialog box, clicking the Point File Formats icon (upper correct) displays the Point File Formats dialog box. It is here that the user defines new, copies, or modifies an existing format. See Figure 2.

Point File Format dialog box.

After clicking New, Copy, or Change, the Betoken File Format dialog box displays. The Bespeak File Format dialog box Coordinate zone transform toggle allows the format to have an assigned system. When this toggle is active, the globe icon calls the Select a coordinate zone dialog box. The systems are the same as those listed in Edit Cartoon Settings for a Civil 3D drawing. See Effigy 3.

Select a coordinate zone dialog box.

After assigning a coordinate system to the format, you should alter the Northing and Easting entries to Filigree Northing and Filigree Easting. To exercise this, in the Point Format dialog box (Effigy 1), click the Northing heading and in the Select Column Name dialog box, click the drop listing arrow, and, from the listing, select Grid Northing. Repeat this for the Easting heading. Subsequently making these modifications, your dialog box should look similar to Figure one.

Transferring Betoken File Formats
If you develop several Point File Formats, they are available only to their drawing. You transfer the formats to other drawings or the template file through the drag-and-drop method used to transfer styles.

To transfer the format to a template, open the template file while still in the drawing containing the new point file formats, and in the Windows menu select Tile Vertically. This allows yous to view both the drawing and the template at the aforementioned time. In the drawing with the new Point File Format, expand Setting's Betoken branch until viewing the Point File Format list. From the listing, select the new Point File Format, and while holding down the left mouse button, drag it to the template file. When lifting upwards on the left mouse push button, the file format is added to the template.

Using a Transformation Point File Format
Selecting a indicate file format with an assigned coordinate organization is only the first footstep to importing and transforming points. After selecting the format and the file to import, you must toggle on Practice coordinate transformation if possible. See Figure 4.

Import Points dialog box.

Afterwards importing the file, you lot should review the original coordinates to the new coordinates in the drawing. Run across Figure 5.

Original and transformed coordinates.

Exporting Points
Having an assigned coordinate arrangement is also bachelor as an export points format. If yous want to consign NAD 83 point coordinates to NAD 27, in the Export points dialog box, you would assign a NAD 27 format, toggle on Exercise coordinate transformation if possible, and when exported, the resulting file contains NAD 27 coordinates.

Surface Definition -- Point Files
When adding point data to a surface, they can come from either a point grouping or directly from a point file. When straight importing points to a surface, the points announced simply as surface points and not cogo_points. The interface for importing points to a surface is the same as the Import points command. If you lot use a point file format that has an assigned coordinate system and wanting to transform the points to the cartoon'south arrangement, following the aforementioned steps mentioned above for importing points will transform them to the drawing's system.

Transformations When Inserting Points From Survey
Related to point file formats with differing coordinate systems, is collecting survey data in ane coordinate organisation and inserting the Survey points into a drawing with a different system. For example, conducting a survey in NAD 83 and inserting its points into a NAD 27 drawing, causes the betoken coordinates to transform from NAD 83 to NAD 27. The Survey command, to create network control points from drawing points, also transforms points from the cartoon coordinate system to the survey arrangement.

In Survey, yous exercise not demand coordinate systems to cause a transformation. If collecting a survey in U.South. foot and inserting survey points into a drawing using international feet will cause the bespeak coordinates to change. Yous must make every effort to keep the survey and drawing units the same.

Summary
Signal File Formats allow y'all to import and export points to assigned coordinate systems. A bespeak format file with an assigned coordinate system dissimilar from the drawing's coordinate system, transforms the betoken'southward coordinates to the drawings coordinate arrangement values. These same formats can exist used to export points coordinates held in one system to a different organization assigned to a Point File Format.

The same Betoken File Formats import points direct to a surface. This process is the same as importing points to a drawing. The difference is importing to a surface does not create cogo_points, but surface points.

The last place transformations occur is when inserting points from a survey into a drawing. If the survey is NAD83 and the drawing NAD27, inserting the points from the survey transforms their coordinates to match their coordinates in the cartoon's coordinate system. Even if using local survey coordinates, if the survey units exercise not friction match the drawing units, the survey bespeak coordinates with transform to match the drawing units. This occurs when surveying in U.S. foot units and inserting them into a drawing set up to international pes units.