<< Click to Display Table of Contents >> Navigation:  Wadiso 6 User Guide > Model input and display of results in the Albion environment > Performing special operations on the system > WGS System Conversion > WGS84 CAD Conversion

The CAD > Tools > WGS > Convert Drawing option allows the WGS transformation of either the entire CAD drawing or only a selection (a pop-up menu will appear where whole drawing transformation or only a selection can be chosen).

A dialog box will then open to enter a few parameters required for the transformation.

The first field is the Block file directory. This directory contains all the .SGD block files. The default is the subdirectory WGS84 under the Wadiso Program Directory (typically c:\program files\wadiso6\wgs84).

Next specify the from and to meridians. This must be an odd integer from 17 to 33 covering the longitudes over South Africa. Normally the same value is used for the from and to meridian. However a shift from one meridian to the other (for example 19 to 21) can also be done as part of conversion.

Select the direction of conversion, by clicking on the corresponding button at the bottom of the dialog box:

 

The Cape to WGS button converts a CAD drawing from the old Cape Datum (Clarke 1880 Projection) to the new Hartebeesthoek94 Datum (WGS84 Projection). The WGS to Cape button does the opposite. The two Lo Trans buttons perform coordinate shift from one meridian (e.g. 19) to a next (e.g. 21) without performing a datum / projection conversion. When performing the coordinate shift the correct button must be applied, i.e. if your data is in Cape then use the Lo Trans(CAPE) button and if the data is in WGS then use the Lo Trans(WGS) button.

Before the conversion / transformation operation commences you will be warned that any changes to the CAD cannot be undone. After the conversion, you will be warned to save and reload the drawing. This is to ensure that the limits of the drawing (used for example when you select Zoom All) can be updated correctly.

Error Messages

The following error message may result:

Orion module not available: The security key has not been updated for the Orion (WGS Conversion) module. Please contact GLS Consulting to purchase the upgrade.

Conversion error occurred – some data not converted. X Entities: Some entities in the drawing could not be converted. This is most likely the case when all or some entities fall outside the area for which you have the block data file(s). Firstly ensure that you are using a Southern Hemisphere coordinate system, and that all the coordinates are real full surveyor coordinates. For example X values (Southings) must be larger than 2 500 000. Then check for any entities of the drawing, which fall far outside the area of the transformation. For example title blocks or grids should not form part of the conversion. Use the selection option to mark only part of your drawing before performing the operation.

The conversion / transformation often encounters a problem with block inserts (an AutoCAD concept, see the Albion CAD online manual for more details). The solution is to explode all blocks before performing this operation. This can be done using the CAD > Modify > Explode command.