GPS - working or broken.......
My understanding of GPS equipment is that the GPS module in ones sat-nav receiver does the bulk of the calculation on the received data and squirts out position, speed, direction and time. The display and map related calculation stuff is done in software in the unit.
Is this correct?
I have a cheap GPS based speed display unit which reads a bit odd. Used in the car I expected it to display a proper accurate reading of speed, more accurate than the car built in speedo. It doesn't. Below 10mph it reads less than the car speedo does, over 10mph is starts to read more than the car speedo which, when compared with other GPS equipment, over reads itself. The comparison GPS equipments I have used are a Garmin Nuvi 2599 car satnav, a Garmin Aera 500 flying satnav and a Garmin 12xl walkers GPS. It is not a Garmin issue! The comparison GPS units all agree with each other and, in previous tests, they agreed with flying GPS systems from Honeywell and Skyforce.
What is going on?
The cheap display I have is the second one I have had. The first unit was supposed to display MPH but actually showed speed in KMH. There are no controls on the items, you just plug them in to a USB for power and wait for lock onto the satellites and you are good to go. nearly.