Is there any way to get current location without using GPS, Wifi and cell tower.
You can derive the lattitude roughly and with big errors, if you analyse the magnetic field, especially if you can ask the user to place the phone on a flat surface, even better if you can ask him or her to have it point north (but that might prove unreliable).
Subsequently ask the user to point the phone to the sun. Use that information to derive the longitude, given that you know time and time zone the phone is set to.
Related
I need to know if the GPS device component of my users is healthy, so i want to get the location ONLY by the GPS and NOT form wifi or surrounding antennas.
I'm forcing my users to close their wifi before this operation so i definitely know that the received signal is not from the wifi (because its possible).
I tried to work with the CLLocationManager and CLLocation's horizontalAccuracy.
some people say that when the horizontalAccuracy is lower than 160 it means we have a good GPS strength, but its not perfect at all..
I also tried to create an array of [CLLocation] after calling [locationManager startUpdatingLocation], and than i saw that when i'm in a place like a basement(with no GPS signal), my array's count was lower that a situation with signal because the updates frequency is lower.. but this is not a perfect solution either..
I just want to be sure that the GPS component is definitely working and the location that i get is from the GPS.
so, any solution please?
I have a requirement mentioned below:
Already have a floor plan map image
First detect current location on floor
Then select the destination location using floor plan map image
Now application should provide direction & distance for that source to destination path
This is like how google direction works, but its in-house map require.
For example,
- Current position of user is: At his desk
- Where is Meeting Room #11
- So application should provide direction and distance updates on the map/floor plan image.
Any kind of suggestions/help would be great.
Thanks in advance
Couple of points...
You could create various audio files and play them as way points based on routing. Same principal as 'turn right at the next light'.
Definitely want to set your accuracy to: kCLLocationAccuracyBest. But this will still probably only get you accuracy of around +/- 10 meters at best.
Do a floor plan overlay using MapOverlayView.
If you are indoor, iPhone uses cell towers or WIFI for a location fix. This might be a problem for you because if you are looking to map multiple floors, only GPS can give you altitude readings - ground floor, second floor, etc...
I don't want to pour cold water on your idea but I have not heard of anyone successfully doing an indoor navigation app on an iPhone using standard stuff. If you really wanted to move forward on this project, your best accuracy might be using indoor bluetooth transmitters as navigational beacons...?
What you want is path-planing in the map, is that? If so, there is lot of algoritms you can use. You can choose a block size based on your map and resolution needs, divide de map into this, amd mark each block as navegable or not. Then getting from the first block trying in the direction of the destionation block, check if the neighboor block is blocked or not, and get going, until you reach (or not, if its not reacheable) the destination block.
Thats a pseudo-implementation, you have some option to do it, if I understand your needs.
(I dont know your hardware as said by others, with simple GPS and indoor navigation, assuming a 15m resolution is a good balance between optimistic/pesimistc signal, If its for robot-navigation, its not a goos approach in the GPS terms, but the algorimt is).
i use CLLocation for a app that record people's trace in map view when they are running or walking ,but i found when my device is still (not moved) ,the
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations is also get called frequently ?
currently ,my locationmanager's desiredAccuracy is 10 meters and distanceFilter is 10.
how to deal with this situation? I have tried use big distancefilter value(like 150) ,but I found if i do this, then i can't record exactly when people is running or walking
GPS is not exact. You can move around a few feet and get the same location. Or you can sit still and get told you have moved a few feet.
You might be able to combine measurements from the accelerometer to determine if you have really moved but this would only work if the device was sitting on a table not moving.
Have you called stopUpdatingLocation after the initial startUpdatingLocation? It will keep updating location if you do not call it.
How does system know whether or not you have actually moved? It MUST fetch your location to find out. The more accurate your desired accuracy is, the more vigorously and frequently it would look. By vigorous I mean if it's suppose to use cell-tower information then it would look into more cell-towers to better triangulate. Or simply put it, the interval between its fetches would be smaller. Concluding: OS would fetch data even if you don't move.
Additionally to triangulate your position the OS (depending on your desiredAccuracy and previous movements) would use a mix of GPS, wifi, Cell-tower. And because someone may all of sudden turn off/on their wifi, or satellite that you were using to get your location has moved a bit or the satellites have changed, or a cell-tower signal may become more or less accurate due to its bandwidth limitations then your calculated location may change which triggers a callback if it's more than your distanceFilter. ( I don't believe you get callbacks for less than your distanceFilter, but I may be wrong) This likely means your distanceFilter is set to very small number which depending on your business requirements may or may not be a good choice. Concluding: your location is never ever 100% accurate
The result of periodical fetching, possibility of error and small distanceFilters lead to possible incorrect locationChanges.
I want to know the accuracy and the distance filter of the low-power significant change location service (i.e if I use startMonitoringSignificantLocationChanges how much it's accurate, and what is the distance of the significant change)?
I need some experimental (non documentary) info from real time apps
I had a chance to speak with the Apple Location Engineers at WWDC this past year and this is how it was explained to me.
The significant location change is the least accurate of all the location monitoring types. It only gets its updates when there is a cell tower transition or change. This can mean a varying level of accuracy and updates based on where the user is. City area, more updates with more towers. Out of town, interstate, fewer towers and changes.
This is also the hardest location type to test for since you can't use the simulator either. I'm not sure if they have fixed it to work with the GPX files for 6.0, but the significant location change api did not work at all in the simulator prior to iOS 6.
I have tried to avoid using the signification location change for many of these reasons. Sometimes it can't be helped. I ended up using the region monitoring API's as they are far more accurate and just as good on battery life. Hope this helps.
From the Apple documentation:
This interface delivers new events only when it detects changes to the
device’s associated cell towers, resulting in less frequent updates
and significantly lower power usage.
There doesn't appear to be much more specific information available about the exact accuracy, so I would assume you have accuracy roughly equivalent to the approximate distance between cell towers in the area that the iOS device is currently located in (which is shorter in more highly populated areas).
I had to build an app back then that uses cell tower significant location changes.
Short answer: very inaccurate.
I was clearly crossing the boundaries of my region.
From what we observe in our app, it can be a few hundred metres to a few kilometres off. Our testing was in the city area, cell towers in suburbs parellel to the train tracks and other suburban cell towers.
Pretty rough.
It was consistent most of the time. I notice that every time I was about to go into the tunnel to the underground train station, it would fire off my 3 region crossing notifications that I have setup for the CBD city area.
I'm using Xcode 4.6.2, and you can indeed simulate significant location change on this simulator.
In the iOS Simulator, the menu entries you need are Debug->Location->Freeway Drive.
Caveats (I welcome being told I'm wrong):
1. After a long while, there seem to be no more significant location change events.
2. You can only drive a pre-defined route in the general Cupertino/SF area. If all you care about is significant location change, that's fine.
Be careful, although you can access the speed property of the location got from the significant location update, it's useless! the simulator actually gives the speed but in real devices the speed is not available because location got from cell towers will not include the actual speed(unlike GPS). more the that as said before the location itself is very inaccurate it can be a few km off.
Be aware of that.
The only way to get the speed is have two cllocation and compute the speed manually
I made a very simple APP in which I can throw a pin right onto the location I am standing at (just a beginner's practice). But I found a problem.
I swear neither I was moving nor the device thought I was moving. And I directly use the geolocation to set the pin. but the pin and the current-location blue point are hundreds of meters apart.
(By the way, the blue point expressed my real location at the time.)
This is a famous problem of Google Map on iOS in China. Put aside the complicated issue of the so-called national security, where I want help is what should we do as a developer. Technically, is there a way, in programming, to figure out what exactly the offset is and correct it?
Does anyone have any idea?
At what time did you place the pin? iOS has up to three sources of location data (cell tower triangulation, Wifi sniffing and GPS) and will keep you up to date with the most accurate. So often you get a not very accurate location, then a more accurate location, then an even more accurate location.
If you have a MKMapView open then something you can do is key-value observe on its userLocation property rather than starting any sort of CLLocationManager. That way you'll always be updated with whatever the map view has decided is the current location, meaning that you don't need to try to match your logic to its.
I did some research on the offset, but haven't gotten a satisfying result yet. The added offset is deterministic, i.e. given a location, the deviated location is fixed. So my goal is to get the deviation function, f(p)=p', where both p and p' are 2D points. You can check here if you are interested.