Hi i know the working principle of GPS. After some R&D on the same, i have some doubts regarding the Global Positioning System
We all know that GPS can work without internet. But will the accuracy be correct in non-remote areas like Desert, mid-sea, dense forest?
I am in an idea to build an app that utilises, GPS in non-remote areas.
Will the GPS works in restricted areas? For example, in Countries border, ocean border and all?
There is a very good article about cell phone GPS accuracy from Community Health Maps. How Accurate is the GPS on my Smartphone? (Part 1 and Part 2)
In this article they explain cell phone A-GPS. The A stands for assisted, in which the phone downloads the GPS ephemeris (data about the GPS satellite constellation). Without data access the GPS may take several minutes to become accurate because the ephemeris would be downloaded from the GPS satellites.
The GPS system does not have border restrictions. It is space based a radio communication. If you have a good view of the sky and have good satellite geometry you can get good positional accuracy. Many new phones now use GNSS instead of GPS. This is US GPS plus Russian GLONASS and other systems. This helps by increasing the number of satellites available, and the GLONASS satellite system is better in high northern latitudes.
Related
I'm building an app using Geofences, right now the minimum radius I can set so my geofence can get accurately detected is 30m. I want to be able to set a minimum radius of 5m.
In the Android Developers documentation about geofences says:
When indoor location is available, the accuracy range can be as small as 5 meters.
What does it mean with the indoor location? Is it something I should enable in the phone? I don't get it. Also I looked over internet and I know that the accuracy of a geofence is perform by the system and cannot get the Wifi RTT or anything else work with it.
What can anyone do to get a better accuracy for geofences?
Indoor location means using bluetooth beacons to determine a more exact location via triangulation. It only works in a predefined area as you need special hardware in the physical location. Getting it down to 5m outside would require GPS hardware more powerful than in the typical phone. The typical phone is accurate to only about 10m in the best case. What you wan't just isn't possible.
Well for triangulation you need to have the direction from which your device is receiving the signal.We can calculate Angle of Arrival for that but calculating that angle requires an array of receivers. Is a cell phone capable of calculating Angle of Arrival? I am asking this because I have came across the terms like wifi/BLE triangulation, calculating position by triangulation etc but they're actually referring to Trilateration in most of the cases. I know how trilateration works for a mobile and all the details but I don't think Triangulation is possible. And if it is possible, how is it possible and which one (triangulation or trilateration) is expected to give better result if you use ibeacons to approximate positions?
Lot of people are misleading terms as you pointed out. Triangulation is not possible with standard ble beacons or WiFi (I mean without modify the standard ble 4.0 or 4.1 and WiFi) right now because the standard doesn't report useful information like the phase (if you have phase and an array of directional antennas that are powered on one per time at a predetermined frequency you can use algorithms like MUSIC and deal with angles) but we only have Rssi and TX power at one meter(if it's an iBeacon) with those information we can estimate the distance that is very imprecise and fluctuate rapidly over time because of multipath and diffraction.
In Nextome we have invented an algorithm to mitigate multipath fading that causes signal to bounce and achieve high accuracy Indoor Positioning of about 1 meter without fingerprinting.
No one has tested triangulation with standard iBeacons right now but trilateration. I would start looking at least square approximation to solve the trilateration problems, but don't expect big results without filtering out the noise.
Mobile mast triangulation usually uses the power level to estimate how far a phone is from a particular cell tower. At any given time a phone will generally be in touch with several towers, even though it is only using one at a time for calls etc.
If you have an estimate of the distance from two or more towers you can imagine drawing a circle around each tower with the radius equal to this distance.
Where the circles intersect is the 'likely' position(s) of the mobile device.
WiFi estimation works on roughly the same principles but is much more accurate as there are so many more WiFi networks.
The big data aggregators (Goggle, Apple etc and their partners) receive data from millions of phones which allows them accurately locate where a particular WiFi network is located. When you then ask your phone to check you position they are able to see what WiFi networks you are close to and vey accurately narrow down your position, especially in a built up area with many WiFi networks.
Most phone positioning systems will use a mix of technologies, GPS, cell strangulation, WiFi to help narrow down your location.
Of course if you are on top of a mountain or in desert the options are a bit more limited, and GPS becomes more important...
On a cloudy day, what will be the output of a GPS device?
from the link http://www.gpsreview.net/10-myths-about-gps/
People often describe GPS receivers as needing a “clear view of the sky”, however the clear view simply replies to not having any obstructions to the view of the sky such as mountains, tall buildings, dense canopy, etc. A cloudy day will not prevent your GPS from working. As an example of this, airplanes can use GPS to navigate down to a runway in cloudy or foggy conditions.
There is no definitive way of knowing if cloudy weather affects the GPS's performance. Additionally, if we were to assume it does affect it, there is no way of knowing for sure what effect it has on the output.
GPS performance also changes from device to device. (I speak purely in this context of Android devices). The 1st generation Samsung Galaxy S is know for it's terrible GPS performance. To the extent that a cursory search on XDA will reveal several attempted fixes plus a few hardware mods too.
In my opinion, however, your statement that cloudy weather affects the GPS performance is a common myth among plenty of GPS users. The first source clearly states that the loss when using GPS in cloudy conditions is a mere 2db. Hardly enough to affect it's performance as you state it does in your app.
Source 1: http://www.gpsinformation.net/gpsclouds.htm
Source 2: http://en.wikipedia.org/wiki/Global_Positioning_System
Extract from Source 2:
The Global Positioning System (GPS) is a space-based satellite
navigation system that provides location and time information in all
weather conditions, anywhere on or near the Earth where there is an
unobstructed line of sight to four or more GPS satellites.
A possible solution: If you think GPS is affected by the weather conditions, you could consider using the Network provider to ensure seamless performance in your app.
I can garuantee, that the GPS signal is not affected by cloudy wheather. GPS is weather proof. A GPS signal has to travel from the satellite through the ionosphere to the receiver. on that way the weather part (where the clouds are located) is a very small band at the end of that path.
GPS is more affected by the sun. At night the signal is slightly better, because the sun causes electrmnagnetic disturbance.
The frequency of the GPS signal is choosen to be outside of the range where water molecules can weaken the signal.
So finally your problem was for sure not caused by cloudy wheather.
The only thing related to weather are wet leafes of trees, which weakens the GPS signals.
(Some receiver have a forrest mode for that purpose)
I'm trying to find a solution for pinpointing indoors, specifically inside big crowded places, like malls for example.
I tried building a simple app that tried to pinpoint the phone using only the Network service or Wifi networks.
Usually when Wifi was on the accuracy got to 40-60 meters, and when the wifi was off and only the network service was used, the accuracy got to 600-1000 meters.
Unfortunately that really is too inaccurate for my needs.
I read that Google have successfully added an accurate solution for indoors navigation ( http://www.engadget.com/2012/01/08/google-maps-indoor-navigation-las-vegas-ces-2012/ ) , so I guess there might be a possible way to achieve a higher accuracy. 5-10 meters accuracy should suffice.
I'd be happy to get any kind of advice!
Thanks!
In highly trafficked public spaces, indoor location solutions tend to be based on WiFi mapping combined with known map information. That approach allows an increase in the accuracy of the location information you will get from your cellular device (over results from testing performed in locations not yet mapped). The actual error rate will depend on how dense and well mapped the WiFi hot spots are, whether they are in stable locations or tend to be moved around, the accuracy of the floor plans, and the effectiveness of the algorithms that integrate the floor plan information (e.g., defining which paths may be navigated by people, for example).
Other organizations are deploying infrastructure in public spaces (e.g., Nokia - Bluetooth-based). This solution assumes you control the infrastructure (and assumes the latest Bluetooth technology).
I work for TRX Systems and we are complementing these existing technologies with sensor and map fusion technology. In this approach, we fuse information from a multitude of sensors - including signals of opportunity (GPS, WiFi, cell triangulation, Bluetooth), embedded sensors (inertial, altimeter, ranging, compass), and known and inferred map information, to deliver an accurate location indoors.
Carol
The only way to accurately estimate your indoor position is by mapping the signal of known radio hotspots (i.e. wi-fi). That's why the indoor navigation feature has been implemented just for a few locations.
I'm creating an application that needs to be very accurate such that when an individual is walking past a certain building, it will provide them with information regarding that building. I was wondering could this be accurate enough using the Android Location API? What technical challenges should I consider?
Edit: I am using a HTC Sensation XE although i'm not sure what chip it uses for GPS
There are multiple variable factors here:
1. GPS hardware itself.
2. Even if the GPS hardware is good,you cannot assume to have very good accuracy since GPS works on "Line of sight"...so if there is lots of trees/high buildings/or anything that could possibly cover the satellite from the GPS receiver would decrease the accuracy of the location determined
3.Time and location---Not all GPS satellites are available in all places at all times...and the accuracy depends on the number of available satellites currently above the user in the sky(to say in lay man terms).
4.The speed of the user.This is more to do with the polling time rather than the GPS accuracy,If say the user is moving in a high speed train,it practically becomes impossible to exactly poll the GPS for the location at that required time thus missing the building.
You might want to understand on how GPS works and this is more of a GPS technology limtation rather than Androids.
Cheers.
Basically the answer depends on your GPS hardware. However, do not expect accuracy of a few meters.
See here for a similar question and some aspects for accuracy: https://stackoverflow.com/a/8852790/1127492
According to this question, accuracy of Android phones' GPS can vary from around 5 to 50 meters, but it mostly depends on the performance of the GPS chips, which has nothing to do with the OS per se.
According to the location API doc, you can also try to use the cell towers and wi-fi hotspot for location, but this will typically be even less precise.