An user sent me the following e-mail:
"Hi ...,
Answer:
Usually a GPS device works in the following way, quite briefly: There is a constellation of GPS satellites (Global Positioning System) in Earth orbit. The device looks for a minimum of three visible and closer satellites, performs a triangulation calculation and gives the coordinates of your position in latitude, longitude and altitude.
"Hi ...,
I've tested the application in the farm on Wednesday to measure a known area in the farm and the result was very good. Today I showed it to a customer in Independência Stadium, inside Belo Horizonte, and it was a complete disaster. What could have happened? I tested it twice, I'd like to send you the generated file, a disaster.
"Answer:
Usually a GPS device works in the following way, quite briefly: There is a constellation of GPS satellites (Global Positioning System) in Earth orbit. The device looks for a minimum of three visible and closer satellites, performs a triangulation calculation and gives the coordinates of your position in latitude, longitude and altitude.
The iPhone, iPad or iPod Touch GPS uses the same type of calculation, but it is necessary that the satellites are visible. If the minimum number of satellites is not visible, it seeks a Wi-Fi network or use the mobile antenna network to give you a position.
However, the accuracy of the coordinates reported falls a lot if it does not use the satellites.
The application iMapIt has no way of knowing whether satellites are being used or not, but has the accuracy and the error that is being used at this time.
When you use the positioning indication button, as illustrated above, the application will zoom in to your current location and display a blue dot with a circle around it. The blue dot is your position, the circle is the current GPS accuracy.
See the image below.
See that the circle of precision occupies several city blocks.
This is one of the worst possible precision... I was not placed where the blue dot is centered, but I was certainly within the circle.
It's not worth to measure anything with such accuracy. The result will be disastrous.
Please note this new image. I stood waiting at the same point ...
The circle and diminished and the blue dot was almost exactly where I was ...
But to survey an area the accuracy is not good yet.
Notice that the blue circle still occupies two city blocks.
He was in the middle of town, so not always the GPS signal is the best. I walked a little, reached out, separated the phone from the body, turned to one side and to another. The accuracy increases, decreases, and ends up putting you in the right spot.
The best accuracy will be seeing when the blue circle disappear. When you get only the blue dot and a pulsing circle around it.
This way your surveys will be "perfect" ...
One tip: get to the point where you want to mark, before taping the MapIt button, wait a few seconds ... You will see the blue dot will gradually positioning itself to get exactly where you are.
If you prefer, use the satellite image map view.
Use this button for that, which is in the upper right corner of the screen. So you know exactly if the blue dot is on your actual physical location.
I hope this helps.
Do not hesitate to ask.
