Have had 2 of these units. Functionality is excellent, but obviously the degree of accuracy depends on how accurately the course was mapped. In most cases the mapping seemed great, but I have come across a few mapping errors. But with both units, after 6-12 months they seemed to have a software problem in loading. The customer service from Sureshot (in Melbourne) was excellent in both cases to get them fixed, even though I had to send unit back to them.