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Coordinate Transformation

The transformation of objects and/or even entire projects is a strong feature of CadnaA.

Import files from third-party software

When files are imported, differences in the coordinate systems may have to be taken into account. The possibility of coordinate transformations exists, therefore, with all import formats available in CadnaA.

Duplicate, displace, rotate, distort objects

In order to duplicate and/or displace a group of objects in a project or just to simply rotate a building - this can be achieved more easily by the coordinate transformation. Apply the command from the context menu or via the dialog Modify Objects, Action „Transformation“ (see also manual „Introduction to CadnaA“).

For the coordinate transformation several possibilities are available:

  • rotation + translation,
  • transformation via match points,
  • affine transformation,
  • geodetic transformation,
  • general transformation,
  • interactive transformation and
  • unit conversion.

A selected transformation is indicated by a check mark on the "Trans." button after closing the Transformation dialog.

Note

Calculated grids cannot be transferred applying these features since a grid is not an object.

Transformation of the directivity vector

When addressing a coordinate transformation to point, line, or area sources the directivity vector is also subjected to the transformation (see Directivity at Industrial Sources).

Rotation + Translation

Enter the coordinates of the pivot, the angle of rotation and the translation in the x, y and z directions. The rotation about the specified pivot is performed first, the displacements follow in the three directions. The pivot is a pair of coordinates to be imported from the project.

Option „Keep Original“

By this option, objects or groups of objects can be duplicated using a transformation. The originals remain at their previous location, only the duplicates are transformed according to the specification.

This option is available for all transformation types.

Example

A building has a corner coordinate x|y= 50|860 m. This is the center of rotation. The duplicate of this building will get rotated by 30° counterclockwise (mathematically positive) with the following settings and shifted to the right by Dx=100 m and up by Dy=100 m.

Match Points

The coordinate transformation option „Match Points“ offers to combine different project files to a new coordinate system. By entering the old and new coordinates for three points the transformation will also correct for bending/shifting.

Enter in the edit boxes Xold and Yold the current coordinates of the corresponding points and enter for Xnew and Ynew the prospective coordinates of these points valid after transformation.

Using a specific number of reference poijts determines the possible transformation:

  • P1 active (a single reference point): corrects for a simple offset.
  • P2 active (two reference points): corrects for an offset, a rotation and a scaling (conformal).
  • P3 active (two reference points): corrects for an offset, a rotation, scaling and a bending (non-conformal).

After transformation the data of the displacement vector in the transformation matrix are shown when opening the Transformation dialog again and selecting the option „Affine Transformation“.

Displacement vector in the transformation matrix after transformation

Affine Transformation

A rotation and/or a scaling is specified by entering the coefficients into the transformation matrix.

In order to rotate all objects by an angle of ϕ about the origin (0|0), the values in the matrix result from:

\(\begin{pmatrix} x_{neu} \\ y_{neu} \end{pmatrix}=\begin{pmatrix} \cos\phi & -\sin\phi \\ \sin\phi & \cos\phi \end{pmatrix}\begin{pmatrix} x \\ y \end{pmatrix}\)

Example

By the example below the objects concerned are rotated by a 90° counter-clockwise about the origin, shifted afterwards by Dx=10 m and by Dy=20 m.

Geodetic Transformation

This option enables to transform objects between different geodetic coordinate systems. For the designation of the geodetic location of objects numerous national and international coordinate systems exist which may have different reference points in addition (datum). The majority of national coordinate systems describe an object’s location in orthogonal coordinates with a local reference point, while global coordinate systems assign the object’s location on the 3-dimensional surface of the Earth by globally defined values for Easting and Northing. So, any point on the Earth’s surface can be stated by specific coordinates.

By this kind of transformation the object’s location given in national geodetic coordinates (e.g. GK, Gauss-Krueger-coordinates) can be transformed to other national or to global geodetic coordinates (e.g. UTM, Universal Transversal Mercator projection).

Using NTv2 reference systems

Besides the standard reference systems, the newer NTv2 reference systems can also be used. The required conversion files (file extension *.gsb) are not supplied with CadnaA. Copy the gsb files (if applicable) to the CadnaA installation directory (path, e.g.: "C:\Program Files\Datakustik\ CadnaA64\NTv2").

A different directory can be defined via an entry in the ini file. For this, the variable NTv2Path=<path> can be specified in the [GeoCoordSys] section of the ini file.

Source Coordinates

Select in section „Source Coordinates“ the coordinate system and the reference point referring to the present object coordinates. By default, the system „UTM (Northern Hemisphere)“ with the reference point „(default)“ is selected. The setting for the median strip is on „(auto)“ by default. With the option „show user-defined coordinate systems only“ activated on dialog „Coordinate System“ (Options menu) just those are listed besides the global and the UTM-coordinate system.

Target Coordinates

Select in section „Target Coordinates“ the coordinate system and reference point the existing object coordinates shall be transformed to. Source and target coordinate system are related to specific reference points. However, useful combinations system-reference will not be filtered when having selecting either items. The selection of appropriate combinations system-reference has to ensured by the user.

Note

In case the reference for the source and/or target coordinates is not known, use a setting „(default)“. If this setting is not effective, an appropriate reference must be determined by trial and error as no logical link between the selected system and the reference exists.

Median Strip

On the list box „Median Strip“ the relevant strip can be selected. There are a maximum of 120 strips with 3 degrees of longitude available. The coordinate systems make use of a different number of strips each (e.g. UTM-system: 60 strips of 6°each, GK-system: 120 strips of 3° or 60 strips of 6° each). When „(auto)“ is selected the information on the strip number is taken from the first two digits of the coordinate value.

General Transformation

When this option is selected, every new value of the three dimensions, Xnew, Ynew und Znew can be assigned an arbitrary nexus of the values of the three coordinates Xold, Yold und Zold of the old system. This enables to correct for any distortion, reflection, and other modification. The following parameters can be used for the expressions:

  • x, y, z: The existing x, y, and z values of a polygon point.
  • ground: Ground height (may require prior triangulation by opening the 3D view or performing a calculation)
  • del: Deletes a polygon point, see example below.
  • int: Interpolates a value, see example below.

Example 1: Converting a rectangle into a parallelogram

The following transformation generates from a rectangle parallel to the axes and a parallelogram which is shifted along the y-coordinate by 500 m to smaller values.

Example 2: Delete polygon points depending on height z

With the „General Transformation“ dialog polygon points from lines and areas may get deleted depending on a user-definable height z of the polygon points. This feature may be useful for objects which have some points with a height of zero while the other ones have heights greater than zero. By this expression for Znew invalid height points of terrain contours get deleted:

iif(z==0,del,z)

using words: „if the height is 0, then delete that point, otherwise do not alter the height“

Of course you may enter a value different from, zero. After confirming with OK the affected points are deleted.

Example 3: Interpolate height z of polygon points

Instead of deleting the points when their z-heights are not valid, the z-height, may also get interpolated depending on the next z-height and the distance between both. To this end, use this expression for Znew:

iif(z==0,int,z)

Of course, a different value instead of zero can be entered. After confirming by OK the points concerned receive interpolated heights.

Interactive Transformation

By the interactive transformation objects can be duplicated or relocated using the mouse, i.e. without entering numerical values via the keyboard. In order to select objects all options on the dialog Modify Objects are available. By clicking in the white area on the screen all types of objects - as before - are addressed.

Note

The interactive transformation is not available via the context menu of individual objects.

Example

All buildings inside the polygon area shall be duplicated and relocated.

To achieve this proceed as follows:

  • Select from the context menu of the polygon the command Modify Objects.
  • Select the action „Transformation“, as range „Inside Polygon“ and the object type „Building“ and click OK.
  • In the subsequent dialog Coordinate Transformation select the type „Interactive Transformation“, check the option „Keep Original“ and click OK.
  • The dialog Interactive Transformation is shown.

Dialog Interactive Transformation (objects under consideration with frame)

The frame displayed delimits all objects addressed by the selection and subjected to the selected action. The following dialog options are available:

Symbol Action
relocate/stretch/turn selected objects
zoom in
zoom out
confirm transformation (close dialog)

  • To relocate the framed objects click with option selected onto the frame and keep the left mouse button pressed.

  • Now move the frame to the desired location and release the left mouse button.

By using zoom in/zoom out a smaller or larger project section will be displayed.

With just translatoric transformation the result will look like this:

Dialog Interactive Transformation (objects under consideration relocated)

  • Close the dialog Interactive Transformation clicking .

After having confirmed the action by „All“ the selected objects will be transformed to the new location.

Interactively transformed building

Stretching/Turning of Objects

Furthermore, the following options are available:

  • By dragging the frame by one of its polygon points the objects selected can be stretched.
  • While keeping the ALT-button pressed the frame including the objects can be turned to a desired angle.

Stretched and rotated buildings

Canceling the Transformation Action

To cancel an interactive transformation without any change close the dialog Interactive Transformation via the symbol „Close Dialog“ on the top right corner ().

Reapply the Transformation Action

When having finalized an interactive transformation the same transformation rule can be reapplied to a further selection of objects. Proceed as follows:

  • After finalized of an interactive transformation select the new group of objects to be transformed as required.
  • Select on the dialog Modify Objects the action „Transformation“, the range, and the objects type/s and click OK.
  • When selecting the type „Affine Transformation“ on the dialog Coordinate Transformation the transformation matrix will be shown.
  • Click OK in order to reapply this matrix to the new selection of objects.

Unit Conversion

When using this transformation type, the source units and the destination units need to be specified.

The source units are those units of length used in the existing file. The destination units are the units of length intended to receive after applying the conversion.

The following options are available for each list box:

  • Meter (m)
  • Feet (ft)
  • Yard (yd)
  • Miles (mi)
  • Nautical miles (nmi)
  • kilometer

Unit Conversion on Data Import

Via the “Options“ button in the import dialogs also the transformation type „Unit Conversion“ can be selected as well. This offers - for example - to convert geometry data in feet into meters during the import operation.

Please consider that the destination units for a unit conversion on import is always in meters (since the calculation basis and the CadnaA internal data has to be in meters).

Import options, Dialog Transform Coordinates with type „Unit Conversion“ selected:Destination units are always in Meters