Ok, I just took mine for a walk with the 100' tapemeasurer. The smallest change I can see is about 20-30'. I walked it and then measured it several times and it all falls in this window. Were I running a boat with the track laid in there is no way I could run and see this tiny amount of change though. remember its a handheld not a big 10x10" display.
This is about what I remembered from the last few years in the Mid East. I use it but have little confidence in it. It isnt accurate enough for me to drive with using the nav feature, Id be missing turns or in folks yard. It is good enough to get ya un-lost though.
Scotty