First time post for me. I volunteer for a non-profit, providing them with mapping and data analysis. The client has asked me to analyze some FlightAware data. They provided me with a .csv file containing flights over northern Alaska for 2014 and 2015. This is my first experience with FA data, so I want to familiarize myself with it before conducting any analysis.
The data contain about 3 million records. Each record represents a point location containing latitude and longitude fields, along with a variety of descriptive fields (flight id, aircraft type, altitude, timestamp, etc).
When I plot a single flight from the data, those points are displayed in a line stretching from the flight’s beginning to end. This is as expected.
However, I notice that about 98% of the points align perfectly with a 1x1 arc-minute (about 1.0 nm N-S by 0.4 nm E-W spacing) lat/long grid. Thus, those flight lines micro-zigzag from one lat/long intersection to another. Subsequent flight lines passing nearby will also be snapped to the same intersection; thus, one intersection may contain multiple points, each from a different flight.
I’m a commercial pilot, and I know that flights do not follow such patterns. I’m assuming, therefore, that someone (FA?) has moved (“snapped”) the actual reported locations to the nearest lat/long intersection.
But wait! The remaining 2% of the points are not snapped to a lat/long grid; they follow a normal flight route, as one would expect. Here’s a screenshot showing the snapped (blue) and non-snapped (red) points:
Additional observations of the non-snapped (red) points:
a) they only occur in 2015
b) they are clustered around Deadhorse and Kuparuk
c) on average they involve aircraft that are lower, slower and climbing; what I would consider to be in a departure configuration. This pattern holds even when comparing the same aircraft type between snapped and non-snapped.
I am confused why only a small minority of the flight points follow a normal routing, while the vast majority are snapped to a lat/long grid. If it is possible to represent the flight points in their correct locations, why have so many been snapped???
The data contain a field named “Estimated position”, which I thought might be relevant. However, all records contain the value NULL, so this does not appear to be a snapping factor.
I’ve searched this forum, along with the FA website and a general internet search for an answer with no success. I welcome your advice.
Also, a tip of the hat to anyone who can direct me to FA metadata, which may contain my answer.