In order for CarDar to set your location it must receive a very accurate GPS signal
which can occasionally take several seconds (or in poor conditions, may not work at all).
Google maps happily uses any GPS or Network signal it can find and initial results
that can be off by several kilometers. As you can imagine, it wouldn't be very useful
to save your parking spot if the GPS was off by 1km or even 100 meters.
With clear weather and in a large open area (like a parking lot), CarDar works great.
Outside factors that interfere with your GPS signal are commonly overcast/cloudy skies
and nearby overhead obstructions. (GPS works very poorly in cloudy, high moisture weather)
GPS relies on GPS satellites to be generally overhead. At times there may not be
enough satellites nearby to receive a strong fix on your location. The solution in
this case is to set your parking spot manually or wait a few minutes.
Also, you may simply need to restart your phone. There have been several reports of
GPS not working at all or giving extremely inaccurate results until a restart was
performed.
Electronic compasses are easily affected by outside factors. Factors include: cars,
metal, magnets, power transformers, missiles, and Magneto to name a few. To use RADAR
you need to be away from large metallic objects and any electronic devices larger than
a pocket watch.
Note: Smartphone belt clips with magnetic flaps are notorious for messing up
smartphone compasses.
Occasionally you need to re-calibrate your compass by waving your device in a
figure 8 pattern for about 10 – 30 seconds. You'll look stupid, but it can restore
the compass completely. In extreme cases it may take numerous times to re-calibrate.
Do not expect RADAR to work while in a vehicle. A running car is a perfect
magnetometer killer.
This is a hardware limitation and the only solution is to understand what causes
interference and avoid them.
RADAR is developed by the Apps
for Android group and available as a free download.