Fixing integer ambiguities is a non-trivial problem, especially if we aim at computational efficiency and high performance (or success rate). For this reason it has been a rich source of Global Positioning System (GPS) research over the last decade. A brief review of ambiguity resolution using the method of Least-Squares AMBiguity De-correlation Adjustment (LAMBDA) and rapid GPS ambiguity resolution for short and long baseline (KTH method) is presented in this article. It continues with some numerical comparisons between two methods with real (float) and simulated GPS data. Finally, we end the paper with conclusions and some remarks. This comparison shows that the results of ambiguity resolution for short baselines are exactly the same using the KTH, LAMBDA and Trimble Total Control (TM)software. Also, for very long baselines these methods and software were not successful in solving ambiguities. However, the success rate of Trimble Total Control software was lower than for the others. This research also shows the exact effect of ionosphere in ambiguity resolution techniques. Any improvement in this area can improve the quality of ambiguity resolution significantly. More research with extra GPS observations in different conditions must be made for better results in the future.