FAQ (frequently asked questions)
1. Why doesn't objects trail match roads that are shown in the map? What is the accuracy of GPS?
Object trail doesn’t coincide with roads shown in the maps because of GPS limited accuracy. GPS accuracy depends on location (geographic latitude, longitude), satellites’ location and ionosphere’s conditions. In perfect conditions (sunny weather, no clouds, in open area, without skyscrapers, woods) accuracy can be about 3 – 5 meters
Usually accuracy is estimated using statistical method CEP (Circle of Equal Probability). This method allows us to consider, that in probability of 50%, object’s coordinates’ error does not exceed designated values. Otherwise, roads in the map not always are defined very precisely (especially considering Eastern Europe). Another possibility is that new roads don’t exist in the map.
2. Why do data transfers from server to application take so long?
Duration of data transfers from server to user application depends on amount of data and speed of Internet connectivity. While object registers many parameters very often grows data quantity. Then transfer time for long requested period of time could be very long. So if you want to increase data transfer time you should decrease requested data time period. One more way to decrease data transfer time is to decrease frequency of object’s parameters data (time T1 should be not 1 minute but 2 – 3 minutes).
3. Why it is impossible to request current object position?
In most cases you are unable to receive information about current object’s location, because it is out of GSM coverage (is in the sea, in deep woods, etc.)
4. It's one or two hours since module sent its data. Why is it not refreshed?
Module is sending data to the server at fixed time. If the connection is not possible (there is no GPRS context), the next sending will be at fixed time. Still You can send the request, and get the latest data. Also profile may define data acquirement less often (i.e. every 10 minutes when object is not moving) and setting allow only full packet sending.
5. Why only yesterdays data is shown?
Either module didn't sent data because it's not time to do it or it couldn't send it because of network problems. Solution is to configure module so it sends data at desired time.
6. How can I know objects location if it is not sending data by GPRS?
You can send a request and get the SMS with 24 coordinates.
7. Why is object changing its coordinates even when engine is off?
It is because of GPS accuracy. If object is standing between tall buildings or in from of the wall, module doesn't see enough satellites to set its exact coordinates. Then each coordinate is calculated with a slight error. Error depends on number of visible satellites. If object is standing between tall buildings or in front of a wall it may not be enough for module to set its position correctly.