Duncan Mitch J, Mummery W Kerry, Dascombe Ben J
Centre for Social Science Research, Central Queensland University, Rockhampton, Australia.
Med Sci Sports Exerc. 2007 Oct;39(10):1851-7. doi: 10.1249/mss.0b013e31811ff31e.
The purpose of this study was to determine test-retest reliability of global positioning system (GPS) units for measuring distance traveled when walking and cycling (AT), and to determine whether GPS unit placement influences accuracy.
Participants (N = 19) completed two walking and cycling trials at self-selected speeds on a measured 1489-m course wearing two Garmin GPS units, worn in lanyard and waistband placements. GPS estimates of travel distance were compared with actual distance, and test-retest reliability was examined. Data-cleaning protocols were developed to remove signal noise. Results are presented for both raw and cleaned data.
For both raw and cleaned data, no significant differences were observed between trials (trial 1 vs trial 2), unit placement (lanyard vs waistband), or AT mode (walk vs cycle) (P >or= 0.05). Both lanyard and waistband units significantly overestimated distance traveled during walking trials (P <or= 0.05), but not cycling trials (P >or= 0.05). The relative technical error of measurement (TEM) of the raw data ranged from 3.74 to 15.51%, and average absolute errors ranged from 5.03 to 8.53% for all trials. A significant position by AT mode interaction was observed for clean data (P < 0.05). Relative TEM for the clean data ranged from 1.42 to 1.98%, and average absolute errors ranged from 0.32 to 1.97%. Intraclass correlations (ICC) were poor to fair for all trials using raw and cleaned data.
Signal noise during unit initialization may adversely affect unit performance; however, application of data-cleaning procedures to remove data associated with signal noise improves unit ability to measure distance. Results suggest that the lanyard position is the optimal placement for units during data collection.
本研究旨在确定全球定位系统（GPS）设备在测量步行和骑行时的行进距离（AT）的重测信度，并确定GPS设备的放置位置是否会影响准确性。
19名参与者在一条1489米的测量路线上以自选速度完成两次步行和骑行试验，试验时佩戴两个Garmin GPS设备，分别置于挂绳和腰带位置。将GPS估计的行进距离与实际距离进行比较，并检验重测信度。制定了数据清理协议以去除信号噪声。给出了原始数据和清理后数据的结果。
对于原始数据和清理后的数据，在各试验（试验1与试验2）、设备放置位置（挂绳与腰带）或AT模式（步行与骑行）之间均未观察到显著差异（P≥0.05）。挂绳和腰带设备在步行试验中均显著高估了行进距离（P≤0.05），但在骑行试验中未出现这种情况（P≥0.05）。原始数据的相对技术测量误差（TEM）范围为3.74%至15.51%，所有试验的平均绝对误差范围为5.03%至8.53%。对于清理后的数据，观察到AT模式与位置之间存在显著的交互作用（P<0.05）。清理后数据的相对TEM范围为1.42%至1.98%，平均绝对误差范围为0.32%至1.97%。使用原始数据和清理后数据的所有试验的组内相关系数（ICC）均为低到中等。
设备初始化期间的信号噪声可能会对设备性能产生不利影响；然而，应用数据清理程序去除与信号噪声相关的数据可提高设备测量距离的能力。结果表明，在数据收集期间，挂绳位置是设备的最佳放置位置。
