While navigator.geolocation.getCurrentPosition from Google Chrome on PC returns position far away about 100 meters it need to be, Google maps (also using on PC) detects it more accurately (10 meters away).
Is there any possibility to determine users location like Google maps do?
Selective Availability phased out a while ago, so it's no longer a matter of the satellite data being degraded to protect from improvised guided missiles.
Nowadays, you're limited by the sensors you use. Many times, the environment and your consumer device will degrade accuracy. But gps hardware isn't the only sensor you have available; nearby wifi networks and other signals can be used to greatly improve your 'gps' accuracy. This is precisely how google manages to have extremely accurate user-positioning services on google maps.
So don't be afraid to use other sources of location to improve the accuracy of your location sensor (which is just navigator.geolocation.getCurrentPosition at the moment). navigator.geolocation seems to be a sensor made from information available to the browser, which alone isn't particularly accurate. Proper gps is accurate to within 8m. More information can be found on the american website for gps.
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I want to fetch the data of a stock. Since the data changes very fast, is there any way to pull the data like 50-100 times a second from trading websites?
And can we implement that using a raspberry Pi 4 8gig model.
RasPi4 should be more than adequate for this task. Both the ethernet and WiFi hardware is capable of connections at these speeds. (Unless you’re running a bunch of other stuff on it.) Consider where your bottlenecks may be, likely ISP or other network traffic). Consider avoiding WiFi in favor of cat5e or cat6. Consider hanging this device off your router (edge) to keep lan traffic lower and consider QOS settings if you think this traffic may compete with other lan traffic.
This appears to be a general question with no specific platform in mind. For stocks, there are lots of platforms to choose from.
APIs for trading platforms often include a method to open a stream. Instead of a full TCP conversation for each price check, a stream tells the server to just keep on sending data. There are timeout mechanisms of course, but it is good to close that stream gracefully (It’s polite since you’re consuming server resources at a different scale. I’ve seen some financial APIs monitor and throttle stream subscribers who leave sessions open.).
For some APIs/languages you can find solid classes already built on GitHub. Although, if simply pulling and reading a stream then the platform API doc code snippets should be enough to get you going.
Be sure to find out what other overhead may be implicated. For example, if an account or API key is needed to open a stream then either a session must be opened first or the creds must be passed with the stream being opened. The API docs will say. If you’re new to this sort of thing, just be a detective and try to infer what is needed. API docs usually try to be precise and technically correct with the absolute minimum word count.
Simply checking the steam should be easy. Depending on how that steam can be handled by your code/script, it may be harder to perform logic on the stream while it is being updated. That’s usually a thread issue or a variable scope issue depending on the script/code. For what you’re doing I would consider Python or PowerShell depending on your skill-set and other design parameters.
Based on this article, when implementing a WebRTC solution without a server, I assume it means SFU, the bottleneck is that only 4-6 participants can work.
Is there a solution that can work around this? For example, I just want to use Firebase as the only backend, mainly signaling and no SFU. What is the general implementation strategy to achieve at least 25-50 participants in WebRTC?
Update: This Github project shares a different statement. It states "A full mesh is great for up to ~100 connections"
Your real bottleneck with MESH is that each RTCPeerConnection will do its own video encoding in the browser.
The p2p concept naturally includes the requirement that both peers should adjust encoding quality based on network conditions. So, when your browser sends two streams to peers X (good download speed) and Y (bad download speed), the encodings for X and Y will be different - Y will receive lower framerate and bitrate than X.
Sounds reasonable, right? But, unfortunately, mandates separate video encoding for each peer connection.
If multiple peer connections could re-use the same video encoding, then MESH would be much more viable. But Google didn't provide that option in the browser. Simulcast requires SFU, so that's not your case.
So, how many concurrent video encodings can browser perform on a typical machine, for 720p 30 fps video? 5-6, not more. For 640x480 15 fps? Maybe 20 encodings.
In my opinion, the encoding layer and networking layer could be separated in WebRTC design, and even getUserMedia could be extended to getEncodedUserMedia, so that you could send the same encoded content to multiple peers.
So that's the real practical reason people use SFU for multi-peer WebRTC.
If you want to make a conference with 25 people all sending their video, then a regular webrtc setup will not work. Except if you massively lower your video quality. The reason for this is that every participant would need to send 24 seperate streams to every other client. So lets say you stream is 128 KB/s then you will need to have 3MB/s in upload speed available. Which isn't always available. Then also downloading that same amount.
The problem is that isn't scalable. That's why you need an SFU. Then you will only send a single stream and receive from others. The other positive thing about SFUs is that you can use simulcast which adapts the quality of your received streams depending on your network speed.
You can use the Janus gateway or mediasoup for example. Here is an already setup mediasoup video conferencing application that is scalable github repository
I'm looking into how one would create a network of embedded systems. What I'd like to achieve is for a device (basically a chip with network capabilities) to directly send data to a server but not use the internet(tcp/ip) or cellular data(like GSM etc).
I don't have much expertise in this field. Most of the networking protocols I've seen like ZigBee are designed for a Local Area Networks. Wide Area Network can be achieved perhaps over mesh or hoping etc. But is there a known protocol for long range networking, say for sensors, assuming there aren't low power constraints?
I am guessing you want to avoid the internet and GSM, not because you have anything against the protocols but because you want your solution to work without having to rely these networks.
If so then you don't have to rule out TCP/IP as this can be used in private networks also.
From your description it sounds like the closest thing that would meet your needs would be a satellite based communications system. So long as you are not worried about price, power and to a certain extend size, then your sensors can communicate from anywhere using satellite links.
There are also HAP - High Altitude Platforms. These are essentially like low flying Satellites, or high flying planes/blimps, so don't have the same coverage but need less power for a given communication bandwidth. If you search for 'High Altitude Platform Networking' you should find plenty of examples such as the following which is an up to date summary of the technology at the time of writing:
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2175-91462016000300249
As mentioned above, many if not all of these systems will support IP based communication protocols on top of their lower layers. Unless you really have some issue with the protocols themselves, it seems sensible to use them as there is such a wealth of experience, tools etc associated with IP communications, and using them does not make you dependent on the wider 'Internet'.
Its also worth mentioning that a common pattern is to have local groups of sensors communicate with each other and or with a gateway and the gateway then communicate over the long link back to your server. This allows the individual device be smaller, cheaper, lower power etc. This may not match your requirements if you are not likey to have clusters of sensors, however.
If you search for satellite sensor networks you may find you get a lot of hits for the gateway case mentioned above. This article 'A Survey of Architectures and Scenarios in Satellite-Based Wireless Sensor Networks: System Design Aspects' looks to be a good overview which includes HAPs also and it is available to download form this site at the time of writing:
https://www.researchgate.net/publication/250003254_A_Survey_of_Architectures_and_Scenarios_in_Satellite-Based_Wireless_Sensor_Networks_System_Design_Aspects
I would look into LoRa which is designed with these requirements in mind.
You still need infrastructure for that (gateways, network servers), you could roll out your own or (in urbanized areas) use pre-existing one like TTN.
The choice of networking technologies depends on many factors, such as range, power constraints, bandwidth requirements and so on.
User Raber already pointed out that you could look into LoRa / LoRaWAN. Since nobody else mentioned it yet, my suggestion is to also have a look at SigFox technology, which is slightly different from LoRa in what it offers and their business model.
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If Chris and Pat want to exchange a text message, they send and receive via their network providers, which charge them for a connection.
If Chris and Pat are both located in New York City, and there are enough wireless devices between Chris and Pat all close enough to each other to form a continuous chain, is it possible for all those devices to be programmed to cooperatively forward packets amongst each other, bypassing the need for network providers?
It would seem the "address" of each device would have to include current geographic coordinates, and devices would have to report their movements frequently enough so routing attempts could still find them, but the speed and capacity of devices nowadays could handle that, right?
Would such a network be viable? Does it already exist or has it been attempted? Is there some kind of inherent programming problem that is difficult to overcome?
There are a few interesting things here:
Reachability. At least you need to use a technology that can do ad-hoc and peer-to-peer networking. Of those technologies only bluetooth, NFC and WiFi are more or less often implemented. Of those again only wifi currently may have the strength to connect to devices in other houses or to the street, but even there typical ranges are 30-60m (and that's for APs, it might be lower for UEs).
Mobility. ANY short-range wireless communication protocol has difficulties with fast-moving devices. It's simple math, suppose your coverage is 50m in diameter, if you move at about 20km/h or 5.5m/s, you have less than 10s to actually detect, connect and send data while passing this link. Oh, but then we did not consider receiving traffic, you actually have to let all devices know that for the next 10s you want to receive data now via this access network. To give an example, wifi connectivity times with decent authentication (which you need for something like this) alone takes a few seconds. 10s might be doable, but as soon we talk about cars, trains, ... it's becoming almost impossible with current technology. But then again, if you can't connect to those, what are the odds you will cross some huge boulevards with your limited reachability?
Hop to hop delays. You need a lot of those. We can fairly assume that you need at least a hop each 20-30m, let's average at 40 hops/km. So to send a packet over lets say 5km you'd need 200 hops. Each hop needs to take in a packet (L2 processing), route it (L3 processing) and send it out again (L2 processing). While mobile devices are relatively powerful these days I wouldn't assume they can handle that in the microseconds routers do. Next to that in a wireless network you have to wait for a transmission slot, which can actually take in the order of ms (each hop!). So all in all, odds are huge this would be a terribly slow network.
Loss. Well, this depends a bit on the wireless protocol, either it has its own reliable delivery protocol (which will make the previous point worse) or it doesn't. In that last case, suppose your wireless link has about .1% loss, or 99.9% no-loss, this would actually end up with an 18.1% loss rate for the 200 hops considered previously ( (1-0.999**200)*100) This is nearly impossible to work with in day-to-day communications.
Routing. lets say you need a few millions of devices and thus routes. For traditional routing this usually takes some very heavy multicore routers with loads of processing power. Let's just say mobile devices (today) can't cut that yet. A purely geographically based routing mechanism might work, but I can't personally think of any (even theoretical) system for this that works today. You still have to distribute those routes, deal with (VERY) frequent route updates, avoid routing loops, and so on. So even with that I'd guess you'd hit the same scale issues as with for example OSPF. But all-in-all I think this is something that mobile devices will be able to handle somewhere in the not-so-far future, we're just talking about computing capacity here.
There are some other points why such a network is very hard today, but these are the major ones I know of. Is it impossible? No, of course not, but I just wanted to show why I think it is almost impossible with the current technologies and would require some very significant improvements, not just building the network.
If everyone has a device with sufficient receive/process/send capabilities, then backbones (ISP's) aren't really necessary. Start at mesh networking to find the huge web of implementations, devices, projects, etc., that have already been in development. The early arpanet was essentially true peer-to-peer, but the number of net nodes grew faster than the nodes' individual capabilities, hence the growth of backbones and those damn fees everyone's paying to phone and cable companies.
Eventually someone will realize there are a million teenagers in NYC that would be happy to text and email each other for free. They'll create a 99-cent download to let everyone turn their phones and laptops and discarded devices into routers and repeaters, and it'll go viral.
Someday household rooftop repeaters might become as common as TV antennas used to be.
Please check: Wireless sensor network
A wireless sensor network (WSN) of spatially distributed autonomous sensors to monitor physical or environmental conditions, such as temperature, sound, pressure, etc. and to cooperatively pass their data through the network to a main location
If memory serves me correctly, google does this for the maps site. I know google's mobile maps app can determine the rough location (I assume using some kind of cell tower lookup), yet I seem to remember the site getting somewhat close to the current location when viewing on a mobile browser.
Anyone know how/if that's possible? Does the IP address change based on the tower or area (seems like they'd be using some kind of gateway common to the carrier)?
With a regular HTTP request the only option you have is GeoIP but this will only give you the country & operator no better.
Depending on the application & device you are using there are various option for geolocation, for example iPhone & Android browsers suport the HTML5 geo javascript functions so you could put some code in the page to send you the location. However these all involve some client side code.
The other option involves doing a deal with the networks, they can supply you the phone number as an additional header in the request and you can then query this number via an API from the operator to get the location of the phone from the network. However they charge a pretty penny for this function and the accuracy can vary from about 100m in an urban environment to 35Km in very rural areas.
This is Not possible.
1.) Location By querying Network Details.
Even if you get the approximate location from an installed app by querying network or cell-id details, it'd not be that reliable. You won't be able to perform anything based on that approximate location.
2.) Location By querying IP.
Secondly, in one country, a single telco will have it geo-stationed GPRS or EDGE gateways and all devices on network are connected to internet with that gateway. So basically you can't rely on location details by IP, because that would be the IP of the Gateway and not the IP of device(in case of EDGE).
Ultimately, if you need to do anything that is based on the location, the
location itself needs be precise and not approximate.
We were using Google Gears for some time and that worked on Windows Mobile version 5.0 plus devices. Google recently stopped that service. Yahoo have now started something called Yahoo Fire Eagle. Sounds good, haven't yet checked it out. I dont have a Yahoo account, yet.
You have Google API Documentation on this:
http://code.google.com/apis/gears/geolocation_network_protocol.html
Hope it helps...
A little late in the day, but another option not mentioned is the MaxMind geo IP lookup. Enter an IP address and it will provide you with a location. There is free service (with simple API) that provides city level accuracy. There is also a more accurate database available for a fee. I have noticed during testing that there are multiple towers / IP addresses in urban areas and the MaxMind database is aware of these. You'll get location, plus the telco provider.
http://www.maxmind.com/