PyGPSClient 1.4.16 / scaling issue in the Scatter Plot widget?

[semuadmin]

Hello,
great program for testing GPS receivers on Linux but I noticed something weird in the Scatter Plot widget:

1. when using the 20m zoom level my track does not fit inside the 20m circle:
   

2. when zooming out to 40m view, the track is well inside the 20m circle:
   

3. when zooming out to 60m scale, the track almost fits inside the 15m circle:
   

To my eyes, the 2nd and 3rd images look consistent while the track in the 1st image looks way too big: either the largest circle should be labeled as 15m or the track is drawn with too large scaling factors.

Best regards,
Matti

[semuadmin]

Hi Matti,

At larger scales, PyGPSClient uses a Great Circle (haversine) formula to approximate distance between two set of coordinates, but this doesn't really work at the smallest scales (5m increments or less). At the smallest scales, PyGPSClient uses a simple Planar formula to approximate distance. This is indicated at the top left of the widget. So the scatterplot will not necessarily be identical at smaller and larger scales, and distances are only approximations - the plot is intended to show broad variability in positioning over time.