Registering shareware usually brings benefits, including support, upgrades and better documentation. Shareware may offer a user limited capabilities of more robust commercial software. For example, The SeisSoft Co. offers several coordinate conversion shareware packages that demonstrate conversion algorithms, but aren't as robust as the commercial versions. In defense of this approach, however, it gives the user an opportunity to test one or more software packages and, as a result, be in a better position to make a choice. Take the time allotted to carefully evaluate the software before purchasing it.
Shareware can be an economical alternative to commercial software.
Freeware is copyrighted, licensed software. Software in the public domain isn't copyrighted and can be published, reproduced and incorporated into other products fully or in part without fees paid to the original authors. The package contains many modules for rendering images, raster and vector manipulation, and image processing. For offline information, write to Center for Remote Sensing and Spatial Analysis, Department of Natural Resources, College Farm Road, Cook College, Rutgers University, New Brunswick, NJ 08903-0231. GMT modules support 20 common map projections and allow users to manipulate datasets and produce illustrations, including simple coordinate plots and contour maps.