The test configuration was an early Garmin 12XL with a 26 dB gain external Micropulse antenna. Note that later manufactured Garmin 12XL receivers may perform differently. However, this effect has a contribution at only the centimeters level in the RMS error and other error statistics. Also shown in the plot is the predicted Rayleigh distribution based on the measured RMS error. The plot below shows the similar plot obtained from 30 days of data using a Garmin eMap.
All distances are in meters.
Entries in bold have their values defined by the type of error so they will always be exact in any set of data. Note the close agreement of the measured ratios to RMS errors in the two tables. The percentages are those within the stated error. The tables below show error measurements six sets of simultaneous tests using two GPS receiver antennas separated by 1.23 meters to avoid interference between the receivers but close enough together to attempt similar receiving conditions. The earlier Garmin 12XL test gave smaller horizontal errors with an external antenna than the above tests with the same Garmin 12XL using the internal antenna.