%%%%%%%%%%%%%%% %%% Purpose %%% %%%%%%%%%%%%%%% Determine cold-start acquistion time for Leadtek GPS receiver in a suburban environment. %%%%%%%%%%%% %%% Data %%% %%%%%%%%%%%% Roof of Bechtel Time | Location | Cold Start | # of Sat. -------------------------------------------------- 8:45 Chessboard 40 sec. 3 8:50 " 55 3 8:53 " 46 3 8:55 " >2 min - 8:59 " 53 3 9:00 " 52 3 9:04 Next to Pines 1:15 3 9:06 " 1:24 3 9:08 " 1:09 4 9:12 " 51 3 9:13 " 36 4 9:14 " 52 3 9:15 " 51 3 9:18 Next to Davis 1:45 3 8:21 " >2 min - 9:27 Under Trees 47 5 9:29 " 20 3 9:30 " 51 4 9:31 " >2 min - 9:34 " 42 5 9:35 " >2 min - 9:38 " >2 min - Roof of Main Stacks Time | Location | Cold Start | # of Sat. -------------------------------------------------- 9:45 Main Stacks 48 5 9:47 " 41 5 9:48 " 51 5 9:49 " >2 min - 9:51 " >2 min - 9:53 " 48 5 9:54 " 39 5 mean = 52.54 median = 51 st. dev. = 17.28 %%%%%%%%%%%%%%%%%% %%% Discussion %%% %%%%%%%%%%%%%%%%%% - Cold-start acquisition time seems to be unrelated to the # of satellites in line of sight. - Geographical data more accurate with four or more satellites - As observed at 'Main Stacks' and 'Under Trees', GPS occasionally fails even if an adequate number of satellites is know to be in line of sight - Small tree canopies, like those at 'Under Trees' do not block GPS signals - Acquisition times might be reduced by setting the receiver's sampling rate rather than power cycling it from the host (mote). To test this, though, it will be necessary to send commands to the receiver.