I have a Fastrax UP501 with the MT3329 chipset and I used http://www.adafruit.com/blog/2012/01/20/new-product-up501-breadboard-friendly-66-channel-gps-module-w10-hz-updates to set everything up for use with MiniGPS via Serial to see how it performs.
Alongside I also tested a Skynav SKM53, which also has the MT3329 chipset (and specs), with exactly the same setup.
Both are positioned next to each other and aimed at clear sky near my window but the performance quite differs when it comes to actually fixing a reliable position.
For some reason the Fastrax UP501 does find a 3D fix but the output keeps scattering degrees in both latitude and longitude, the Skynav SKM53 also find a 3D fix but does provide a stable latitude and longitude (which I found more accurate as well). The result is that the Fastrax UP501 always gives a speed output around 1.0 km/hour, whereas the Skynav SKM53 practically always stays down at 0.0 km/hour. (cold start takes about a minute and both find a good amount of satellites.
I attached a screenshot of them running at the same time (after about an hour).
I like the Fastrax UP501 more for its smaller form factor and pin spacing, but rather have better accuracy when I'm going to use it in a project.
I wonder whether this is normal, if anyone found the same behavior and whether there is a solution?