In many of the posts to follow I hope to compare the effectiveness of different input options and algorithm modifications to the position solution. To do this it will be useful to have a single representative set of raw data to use for comparisons as well as a set of metrics to compare. I will discuss the metrics in a future post, here I put together a data set that I believe will be a good test, at least for my goals.
My interest is in relatively low velocity scenarios with open skies (I’ll talk more about the details in another post). To generate my reference data sets, I mounted two Ublox M8N receivers with basic patch antennas on top of a car, both antennas sitting on the metal roof for a decent ground plane. I then collected about twenty minutes of data with the car stationary, followed by driving around in circles in a open parking lot (no nearby trees or buildings) for roughly another twenty minutes, followed by another twenty minutes of driving on open roads with some nearby trees at higher speeds. The low velocity circles are what I am most interested in, but collected the other data to allow additional comparisons under different conditions.
I am fortunate enough to have two CORS base stations within 10 km of where I collected my data and so I downloaded the data for both stations (ZDV1 and TMGO) for the same time period. ZDV1 is GPS data only, TMGO includes both GPS and GLONASS data. That gives me four sets of data. Two are from Ublox M8N receivers with patch antennas, both moving but staying a constant distance from each other, both containing only single frequency (L1) data. The other two are dual-frequency (L1 and L2), fixed position. For consistency, I will use this set of data when comparing results in most of my future posts. Here is a link to a zipped copy of all four data sets in case they may be of use to anybody else. In the file names, “cga” refers to data from the M8N receiver bought from CGA, and “ebay” refers to data from the M8N receiver bought on Ebay.