elcome to the first issue of The GPS Toolbox. This is a new column in GPS Solutions dedicated to highlighting algorithms utilized by GPS engineers and scientists. Contributing authors will be asked to explain how the algorithm they submit can be used for a GPS-related application and to enumerate its advantages and disadvantages. Readers are encouraged to try out the algorithms presented here and to submit alternative ones when applicable. In other words, we hope to instigate a dialog among engineers and scientists about alternative solutions to many different GPS problems. Whenever possible, related source code will be posted (http:// www.ngs.noaa.gov/gps-toolbox). Readers are encouraged to translate this code to various computer languages to suit their needs. Such translated code can then be posted on the Web site for the benefit of other readers. Guidelines for submitting source code will be available on the Web site. To submit an algorithm for publication in this column, follow the Information for Contributors listed on the back cover of GPS Solutions. If you have an interesting algorithm you would like to share with