Pitney Bowes MapInfo Vertical Mapper - Manual (Page 151)

Chapter 8: Using the Grid Tools
User Guide
149
The Reproject tool enables you to perform a preliminary transformation test using the chosen
projection.
The test calculation involves projecting the bottom left and upper right points of the original grid into
a new projection and then back again. The difference in the position between the original and
transformed sets of locations is measured and compared to the original. Most coordinate
transformations return error values less than 0.0000001%. However, not all transformations are
considered “appropriate” and may be characterized by greater error.
For example, you may want to reproject a map covering a portion of North America in Universal
Transverse Mercator (cylindrical) projection to a Lambert Azimuthal (conic) projection centred on the
South Pole. This would return a transformation error approaching 10 percent. The reproject
algorithm will return a message if the transformation test returns an error >0.02 percent and will
discontinue the calculation.
Exploring the Reproject Grid Dialog Box
The Grid list box enables you to choose the name of the grid to reproject.
The Old Projection box displays the original projection of the grid.
The Old Cell Size box displays the original cell size of the grid.
The New Projection box displays the new projection or the message “Choose a Projection!” if the
new projection has not yet been chosen.
The Projection button opens the Choose Projection dialog box, enabling you to choose the new
projection.
The New Cell Size box enables you to specify a new cell size.