Limitations due to RST units

Because GDB deals with an RST in which the units are Meters on the Ground, while MapInfo uses line widths in pixels and symbol sizes in points, GDB must perform an approximation while converting between the MapInfo file and the RST. Fortunately, text sizes are already attached to Ground units in MapInfo, therefore in this case GDB does an exact conversion.

To map pixel and points sizes to ground meters, GDB makes the assumption that the data set is intended to be viewed on a 1280 pixel wide screen, where each pixel is 0.28mm wide. With these values and the file's extents, GDB can convert MapInfo line widths and symbol sizes to/from the RST.

Another approximation is required if the data set's projection is LAT/LONG. In this case, GDB must remap the representation information (for text height) from degrees to meters in the RST. The heights in degrees are converted as though we were dealing with a perfect sphere with a radius of 6370997m. Thus, a text height of 1 degree is approximated to 111195 meters in the RST.