Several months ago, a GPS watch manufacturer published an "advertorial" in the Washington Running Report in which the author claimed that using its product would provide runners with "precise" measurements of the distances they run. I took exception in a letter to the editor, and WRR then published a brief article on course measurement. The article avoided the GPS issue.
Nevertheless, in the D.C. area, it seems to me that there are fewer complaints about certified courses being "long" recently. I am not certain why this may be. My naive hope is that GPS wearers are becoming more knowledgeable about what these devices can and cannot do, and how to benefit from them.
I assume some runners have become aware that civilian-grade GPS devices have a built-in accuracy limitation. Does anyone know what the resolution difference is between Standard Positioning Service (SPS) and Precise Positioning Service (PPS)? Can anyone say what the expected difference in measurement accuracy might be between these two technologies?