Here's an interesting scenario I came upon yesterday and I wanted to throw it out as a question to try help me visualize what is happening.
I have a single point (a person, say) who is looking for the nearest transit station. The person's location is in Lat/Long and the transit station is a dataset in UTM.
To do a nearest neighbor I need to reproject either the person into UTM (to match the transit dataset) or the transit dataset into Lat/Long (to match the person).
If I reproject the person to UTM, the nearest neighbor tells me the nearest transit station is X
If I reproject the transit stations to Lat/Long, the nearest neighbor tells me the nearest transit station is Y
So... does it make sense that the nearest neighbor can be different depending on which coordinate system you are working in? My gut feeling is yes, because Lat/Long is a geographic coordinate system and UTM isn't.
Am I right? I think so but am just having problems visualizing why! In particular, which one of the results is "correct"?