I've run into an issue using the network analyst and I'm hoping others may have some suggestions.
Last year I used the network analyst closest facility tool to identify the supermarket located in closest proximity to each participant in a dataset. I recently decided to run a slightly different analysis and started by rerunning the closest facility tool using the exact same data. However, when I compared the results, 11 out of 197 observations were inconsistent (i.e. different supermarkets were identified as the closest facility).
I put the inconsistent results into Google Maps just to check out what was going on and the discrepant supermarkets appear to be about equidistant from the given participant’s home, so it doesn’t appear that there are any major errors in how the closest facility is being determined, just minor discrepancies. I've attached a screenshot where you can see the home, closest facility, and route highlighted on the left, and the previously identified closest facility highlighted on the right.
I am now working at a different institution than when I ran the first analysis and I'm wondering if the network datasets are slightly different? Both institutions use the pre-built SDC street networks provided by ESRI, but maybe they’re from different years? Or maybe I am specifying slightly different options when I run the analysis? I only recall using the default options previously, which is what I am also doing now, but it’s possible that I specified a slightly different option before.
Has anyone encountered this? Any thoughts are greatly appreciated. Thank you.