topic Re: How to use external gps location data in ArcGIS Runtime SDK for iOS Questions

How to use external gps location data

ShiminCai — Fri, 04 May 2018 05:02:21 GMT

Hi All,

I have a new requirement for our apps to use external gps location updates (Bad Elf GPS Unit) besides the default Apple location service updates. I understood that I need to create a custom location display data source class that conforms to the protocol <AGSLocationDisplayDataSource> and replace the mapVidw.locationDisplay.dataSource. My question is that: how do I implement the start method in the protocol of <AGSLocationDisplayDataSource>? I'm currently still on 10.2.5 and later will look at the 100.2.1 as well. Can anyone please shed any light on this or have any working code to share? Many thanks for your help.

Cheers,

Shimin

Re: How to use external gps location data

DiveshGoyal — Fri, 04 May 2018 17:52:39 GMT

You do not necessarily need to implement a custom location datasource.

If you successfully pair your external GPS receiver with the device, then iOS should start using the location feed coming from the receiver instead of the in-built sensor. That location feed will come through to all apps using the standard Apple location manager apis, which is what the default

AGSCLLocationDataSource uses, so you don't need to build a custom location datasource.

You really only need a custom datasource if you want to use special apis/sdk that the manufacturer provides for pulling extended or proprietary information from the receiver, or if you want to add additional intelligence in the datasource for dealing with location updates

Re: How to use external gps location data

ShiminCai — Sun, 06 May 2018 23:57:02 GMT

Hi Divesh,

Thank you very much for your reply. I'm getting a Bad Elf GPS Unit and will be testing that out.

The Bad Elf GPS has its own sdk/api to pull so much info from the receiver. I think soon or later I will be asked to read other extended infos from the receiver and in this case I will have to implement a custom location datasource as you suggested.

I think I also have another use case of custom location datasource: location feed from drones. One of our projects looks at getting drone location and drone status (pitch, roll, yaw and gimbal) using the drone api. It was proposed that the project/app transmit the location data obtained from drones to an ad-hoc peer to peer wireless connected device using the Apple's MultiPeer Connectivity framework. Thus our apps will need to use the location feeds from drones and that's why I'm thinking the custom location datasource class... Any advises on this as well please?

So any advises on how to implement a custom location datasource or directions leading to any documentation about it would be much appreciated, and everyone please?

Cheers,

Shimin

Re: How to use external gps location data

ShiminCai — Mon, 07 May 2018 03:06:28 GMT

Hi Divesh,

Just found out that our users have already tried what you suggested pairing Bad Elf GPS receivers and their devices and had the problem of iOS switching location feeds from external GPS receiver and the in-built sensor randomly. They want to be able to control the source of location feeds. Looks like the custom location datasource is the way for me to go...

Cheers,

Shimin

Re: How to use external gps location data

Nicholas-Furness — Tue, 15 May 2018 13:10:17 GMT

HI Shimin Cai,

If you're still looking to implement your own data source, look at the reference doc here.

Here's what you need to do.

Implement a class that inherits from AGSLocationDataSource. The key functions you need to implement are doStart() and doStop(). These are the entry points to your class.

<< Runtime communicating to your custom location data source:

doStart() will be called by the Runtime when you call AGSMapView.locationDisplay.startWithCompletion().
doStop() will be called by the Runtime when you call AGSMapView.locationDisplay.stop().

>> Providing feedback to Runtime during startup/shutdown:

Starting your external device - When Runtime calls your doStart() function, you need to tell Runtime once the external device has started up. Call self.didStartOrFailWithError:() from within your doStart() function to let the Runtime know your external device has started or that it failed to start.
Stopping your external device - When Runtime calls your doStop() function, you need to tell Runtime once the external device has stopped. Call didStop() from within your doStop() function to let the Runtime know your external GPS device has stopped.

>> Providing location updates to Runtime:

Getting a new location - Whenever your external device's API gives you a new location, construct a new AGSLocation object and pass it to self.didUpdateLocation:().
Getting a new heading - If you get a new heading only (and not a completely new location), call self.didUpdateHeading:() with the new heading to let the Runtime know.

Hope this helps.

Cheers,

Nick.

Re: How to use external gps location data

ShiminCai — Tue, 15 May 2018 23:09:47 GMT

Hi Nick,

Thanks a lot for your reply. Yes I will be implementing the custom location display datasource. I figured out what to do after reading the relevant docs in the 100.2.1 which provide clearer explanations about the custom datasource than that in the 10.2.5. Your instructions here verified what I'm thinking to do and are much appreciated.

I also had a look at the external gps receiver support of the Collector app. Basically we would like to achieve the similar functionalities in our apps. Did Collector implement the support in a similar way or do you have any suggestion?

I'm currently looking at the gps hexadecimal string data/NMEA sentences. I haven't found a complete NMEA parser in Swift in the net and had the feeling I have to write it myself... Any advises please?

Thanks,

Shimin

Re: How to use external gps location data

Nicholas-Furness — Wed, 23 May 2018 00:45:45 GMT

Hey Shimin Cai,

Collector does indeed take a similar approach.

For inspiration you could look at this C# NMEA Parser. You would have to translate from C# to Swift but there might be some useful info for you there in building your Location Data Source.

Cheers,

Nick.

Re: How to use external gps location data

ShiminCai — Wed, 23 May 2018 07:33:15 GMT

Hi Nick,

Thanks for your reply. NMEA Parser is not a problem. I wrote a simple one and it works fine.

But I'm having trouble making the custom datasource to work and hoping you can help me out. Here is my simple implementation of the custom datasource for trying it out. Sorry I'm still on 10.2.5.

import UIKit

import ExternalAccessory

class FCNSWGPSLocationDataSource: NSObject, AGSLocationDisplayDataSource

{

var delegate: AGSLocationDisplayDataSourceDelegate!

var error: Error!

var isStarted = false

var sessionController: SessionController!

var accessory: EAAccessory?

required public init(sessionController: SessionController)

{

self.sessionController = sessionController

self.accessory = sessionController._accessory

}

func start()

{

NotificationCenter.default.addObserver(self, selector: #selector(sessionDataReceived), name: NSNotification.Name(rawValue: "EXGPSSessionDataReceivedNotification"), object: nil)

NotificationCenter.default.addObserver(self, selector: #selector(accessoryDidDisconnect), name: NSNotification.Name.EAAccessoryDidDisconnect, object: nil)

let sessionOpened = self.sessionController.openSession()

self.isStarted = sessionOpened

if sessionOpened

{

self.delegate.locationDisplayDataSourceStarted(self)

}

else

{

self.error = NSError(domain: "", code: -1, userInfo: [NSLocalizedDescriptionKey: "Failed to open an EA session."])

self.delegate.locationDisplayDataSource(self, didFailWithError: self.error)

}

func stop()

{

NotificationCenter.default.removeObserver(self, name: NSNotification.Name(rawValue: "EXGPSSessionDataReceivedNotification"), object: nil)

NotificationCenter.default.removeObserver(self, name: NSNotification.Name.EAAccessoryDidDisconnect, object: nil)

self.sessionController.closeSession()

self.isStarted = false

self.delegate.locationDisplayDataSourceStopped(self)

}

// MARK: - Session Updates

func sessionDataReceived(_ notification: Notification)

{

if sessionController._dataAsString != nil

{

let rawNMEAString = sessionController._dataAsString!

let nmeaSentences = rawNMEAString.components(separatedBy: "\r\n")

var rmcData: RmcData!

var ggaData: GgaData!

var gsaData: GsaData!

for nmeaSentence in nmeaSentences

{

if let nmeaData = NmeaParser.parseSentence(data: nmeaSentence)

{

if nmeaData.isKind(of: RmcData.self)

{

rmcData = nmeaData as! RmcData

}

else if nmeaData.isKind(of: GgaData.self)

{

ggaData = nmeaData as! GgaData

}

else if nmeaData.isKind(of: GsaData.self)

{

gsaData = nmeaData as! GsaData

}

if rmcData != nil

{

let coordinate = CLLocationCoordinate2D(latitude: rmcData.latitude, longitude: rmcData.longitude)

//these are just for testing purposes and the real data should come from the GGA and GSA sentences

let altitude = CLLocationDistance(0)

let horizontalAccuracy = CLLocationAccuracy(0)

let verticalAccuracy = CLLocationAccuracy(0)

let clLocation = CLLocation(coordinate: coordinate,

altitude: altitude,

horizontalAccuracy: horizontalAccuracy,

verticalAccuracy: verticalAccuracy,

course: rmcData.course,

speed: rmcData.speed,

timestamp: rmcData.timeStamp)

let agsLocation = AGSLocation(clLocation: clLocation)

self.delegate.locationDisplayDataSource(self, didUpdateWith: agsLocation)

self.delegate.locationDisplayDataSource(self, didUpdateWithHeading: rmcData.course)

}

// MARK: - EAAccessory Disconnection

func accessoryDidDisconnect(_ notification: Notification)

{

let disconnectedAccessory = notification.userInfo![EAAccessoryKey]

if (disconnectedAccessory as AnyObject).connectionID == accessory?.connectionID

{

}

In the above codes the sessionController is from Bad Elf sample app which communicates with the connected accessory to retrieve nmea string data. I think this bit works fine as I can get valid nmea sentences as shown below and the latitude and longitude creating the agsLocation object are correct:

I create an instance of my custom datasource class and set the mapView.locationDisplay.dataSource with the instance. Then after the map fully loads, if I try to invoke the mapView.locationDisplay.startDataSource(), the map always zooms to the centre of the map and displays the gps symbol there, not the expected current location. I checked the mapView.locationDisplay.location and mapLocation() and they are all nil. Obviously the location update did not get to pass through to the location display. What did I do wrong? By the way, Collector does the correct thing with the same gps device!

Thank you very much for your help.

Shimin

Re: How to use external gps location data

Nicholas-Furness — Wed, 23 May 2018 11:24:09 GMT

I'm still checking to see if this is a requirement, but you could try dispatching the AGSLocationDisplaySource delegate calls to the main thread. If the sessionDataReceived notification is being fired (and so received) on a background thread I could see that could potentially cause problems.

Re: How to use external gps location data

ShiminCai — Wed, 23 May 2018 23:07:48 GMT

Hi Nick,

Tried your suggestion but it did not help:

DispatchQueue.main.async {

self.delegate.locationDisplayDataSource(self, didUpdateWith: agsLocation)

self.delegate.locationDisplayDataSource(self, didUpdateWithHeading: rmcData.course)

}

Below are the sessionController codes and hopefully it'll help figure out the problem.

Thank you

Shimin

See LICENSE.txt for this sample’s licensing information

Abstract:

Controller for managing connected accessory and communicating with the accessory via NSInput & NSOutput streams.

import UIKit

import ExternalAccessory

// FIXME: comparison operators with optionals were removed from the Swift Standard Libary.

// Consider refactoring the code to use the non-optional operators.

fileprivate func < <T : Comparable>(lhs: T?, rhs: T?) -> Bool {

switch (lhs, rhs) {

case let (l?, r?):

return l < r

case (nil, _?):

return true

default:

return false

}

// FIXME: comparison operators with optionals were removed from the Swift Standard Libary.

// Consider refactoring the code to use the non-optional operators.

fileprivate func >= <T : Comparable>(lhs: T?, rhs: T?) -> Bool {

switch (lhs, rhs) {

case let (l?, r?):

return l >= r

default:

return !(lhs < rhs)

}

// FIXME: comparison operators with optionals were removed from the Swift Standard Libary.

// Consider refactoring the code to use the non-optional operators.

fileprivate func > <T : Comparable>(lhs: T?, rhs: T?) -> Bool {

switch (lhs, rhs) {

case let (l?, r?):

return l > r

default:

return rhs < lhs

}

class SessionController: NSObject, EAAccessoryDelegate, StreamDelegate {

static let sharedController = SessionController()

var _accessory: EAAccessory?

var _session: EASession?

var _protocolString: String?

var _writeData: NSMutableData?

var _readData: NSMutableData?

var _dataAsString: NSString?

// MARK: Controller Setup

func setupController(forAccessory accessory: EAAccessory, withProtocolString protocolString: String) {

_accessory = accessory

_protocolString = protocolString

}

// MARK: Opening & Closing Sessions

func openSession() -> Bool {

_accessory?.delegate = self

_session = EASession(accessory: _accessory!, forProtocol: _protocolString!)

if _session != nil {

_session?.inputStream?.delegate = self

_session?.inputStream?.schedule(in: RunLoop.current, forMode: RunLoopMode.defaultRunLoopMode)

_session?.inputStream?.open()

_session?.outputStream?.delegate = self

_session?.outputStream?.schedule(in: RunLoop.current, forMode: RunLoopMode.defaultRunLoopMode)

_session?.outputStream?.open()

} else {

print("Failed to create session")

}

return _session != nil

}

func closeSession() {

_session?.inputStream?.close()

_session?.inputStream?.remove(from: RunLoop.current, forMode: RunLoopMode.defaultRunLoopMode)

_session?.inputStream?.delegate = nil

_session?.outputStream?.close()

_session?.outputStream?.remove(from: RunLoop.current, forMode: RunLoopMode.defaultRunLoopMode)

_session?.outputStream?.delegate = nil

_session = nil

_writeData = nil

_readData = nil

}

// MARK: Write & Read Data

func writeData(_ data: Data) {

if _writeData == nil {

_writeData = NSMutableData()

}

_writeData?.append(data)

self.writeData()

}

func readData(_ bytesToRead: Int) -> Data {

var data: Data?

if _readData?.length >= bytesToRead {

let range = NSMakeRange(0, bytesToRead)

data = _readData?.subdata(with: range)

_readData?.replaceBytes(in: range, withBytes: nil, length: 0)

}

return data!

}

func readBytesAvailable() -> Int {

return (_readData?.length)!

}

// MARK: - Helpers

func updateReadData() {

let bufferSize = 128

var buffer = [UInt8](repeating: 0, count: bufferSize)

while _session?.inputStream?.hasBytesAvailable == true {

let bytesRead = _session?.inputStream?.read(&buffer, maxLength: bufferSize)

if _readData == nil {

_readData = NSMutableData()

}

_readData?.append(buffer, length: bytesRead!)

_dataAsString = NSString(bytes: buffer, length: bytesRead!, encoding: String.Encoding.utf8.rawValue)

NotificationCenter.default.post(name: Notification.Name(rawValue: "EXGPSSessionDataReceivedNotification"), object: nil)

}

fileprivate func writeData() {

while _session?.outputStream?.hasSpaceAvailable == true && _writeData?.length > 0 {

var buffer = [UInt8](repeating: 0, count: _writeData!.length)

_writeData?.getBytes(&buffer, length: (_writeData?.length)!)

let bytesWritten = _session?.outputStream?.write(&buffer, maxLength: _writeData!.length)

if bytesWritten == -1 {

print("Write Error")

return

} else if bytesWritten > 0 {

_writeData?.replaceBytes(in: NSMakeRange(0, bytesWritten!), withBytes: nil, length: 0)

}

// MARK: - EAAcessoryDelegate

func accessoryDidDisconnect(_ accessory: EAAccessory) {

// Accessory diconnected from iOS, updating accordingly

}

// MARK: - NSStreamDelegateEventExtensions

func stream(_ aStream: Stream, handle eventCode: Stream.Event) {

switch eventCode {

case Stream.Event():

break

case Stream.Event.openCompleted:

break

case Stream.Event.hasBytesAvailable:

// Read Data

updateReadData()

break

case Stream.Event.hasSpaceAvailable:

// Write Data

self.writeData()

break

case Stream.Event.errorOccurred:

break

case Stream.Event.endEncountered:

break

default:

break

}

Re: How to use external gps location data

Nicholas-Furness — Wed, 23 May 2018 23:35:53 GMT

If you log the AGSLocation to the console from within the dispatch to main, does it look correct?

Re: How to use external gps location data

ShiminCai — Thu, 24 May 2018 00:09:30 GMT

Hi Nick,

it looks ok to me. I think the 4326 is WGS84.

Thanks,

Shimin

Re: How to use external gps location data

ShiminCai — Thu, 24 May 2018 00:29:17 GMT

Hi Nick,

Sorry Nick. Checked again and the coordinate does not look correct at all. It is NOT my current location! Something went wrong with my calculation from nmea string to lat and lon. I'm checking now and will report back here.

Thanks you very much for picking this up!!!

Shimin

Re: How to use external gps location data

ShiminCai — Thu, 24 May 2018 01:24:51 GMT

Hi Nick,

Found the cause of the problem that is convert minutes to decimal degrees where I was using 3 (probably a typo) in the second offsetBy. Now after changed to 2 things start working as expected!!!

/// Lat stringValue Format XXYY.ZZZZ -> XX° + (YY.ZZZZ / 60)°

func convertLatitudeToDegree(with stringValue: String) -> Double {

return Double(stringValue.substring(to: stringValue.index(stringValue.startIndex, offsetBy: 2)))! + Double(stringValue.substring(from: stringValue.index(stringValue.startIndex, offsetBy: 2)))! / 60

}

I think my problem has been resolved. Thank you very much for your help.

Cheers,

Shimin

Re: How to use external gps location data

Nicholas-Furness — Thu, 24 May 2018 16:43:13 GMT

Great stuff. Glad it's working!

Nick.

Re: How to use external gps location data

MuruganandhamKuppan1 — Thu, 30 Aug 2018 08:00:04 GMT

Hi @Nick, Its working for me.. thanks

Re: How to use external gps location data

Nicholas-Furness — Thu, 30 Aug 2018 16:04:43 GMT

Thanks Muruganandham Kuppan‌. Great to hear. Could you mark your original question as answered please? It'll help other people home in on the right answer.

Re: How to use external gps location data

ManasaParida — Sun, 30 Sep 2018 09:18:24 GMT

Hi Divesh Goyal‌,

What is the actual process to test the Navigation in either device or simulator when we are in development mode using ArcGIS Runtime SDK, like it is not possible to debug when we only really travel to get new AGSLocation Data so rather than doing that, is there any options to test the static points like Source to Destination with realtime Testing and Debugging when we are developing the app. Would be appreciate if you could suggest me on this. Meanwhile the question is how to test and debug the app in Device/Simulator on realtime without traveling and it was not so feasible to debug when we are traveling . So basically we can set the Source and Destination Route Stops in a JSON file format or something like that once the map loaded it will start navigating the app based on the JSON Route stops so that we can able to test for the re-routing and realtime navigation to found dead code or faulty/bugs to fix it rather than a Real Test.

Re: How to use external gps location data

Nicholas-Furness — Mon, 08 Oct 2018 17:42:00 GMT

You could record a journey to a GPX file using GPS tracking software of your choice and then test your Runtime app using the AGSGPXLocationDataSource. Create a new instance of that pointing at your GPX file, then set your mapView.locationDisplay.dataSource to this new instance.

Re: How to use external gps location data

ManasaParida — Fri, 25 Jan 2019 14:30:23 GMT

@Nicholas Furness Ignore my previous reply, i found the solution to work, thanks