Managing geolocation and GPS

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Overview
Implementing the GPS management
Checking whether the GPS is enabled
Be notified when the GPS status changes
Following the move
Ending the use of GPS functions
When to use each function?
Functions available according to the platforms
Summary table

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WEBDEV

WINDEV Mobile

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Managing geolocation and GPS

Overview

WINDEV Mobile and WEBDEV allow you to exploit geolocation and GPS features found on mobile devices and browsers.

In the phone applications, you have the ability to:

Get information about the last known location of the device.
Ask to be notified when the device comes near a specific area.
Find out the current location of the device.
Retrieve an address.
...

Implementing the GPS management

Checking whether the GPS is enabled

To check whether the GPS is enabled, all you have to do is use GPSStatus.

Example:

// Is the GPS enabled?
IF GPSStatus() = gpsEnabled THEN
Error("The GPS cannot operate.", ...
"It must be enabled to access this application.")
EndProgram()
END

Be notified when the GPS status changes

To be notified when the GPS status changes, all you have to do is call GPSStatus and specify the name of procedure used to manage the current GPS status.

Example:

GPSStatus(_ChangeOfGPSStatus)

The procedure code is as follows:

PROCEDURE _ChangeOfGPSStatus(Status)

IF CurrentStatus = Status THEN RETURN

CurrentStatus = Status

EndTimerSys(TIMER_RETRIEVAL)

SWITCH Status
CASE gpsEnabled
// The provider was enabled by the user.
STC_Status = "GPS enabled"
CASE gpsDisabled
// The provider was disabled by the user.
STC_Status = "GPS disabled"
CASE gpsOffService
// The provider is off service.
STC_Status = "GPS off service"
CASE gpsUnavailable
// The provider is temporarily unavailable.
STC_Status = "GPS unavailable"
CASE gpsAvailable
// The provider is available.
STC_Status = "GPS available"
// Asks to follow the move with a maximum time between two calls to
// GPSFollowMovement(_GetLocation, 1000)
OTHER CASE
END

In this procedure, if the GPS is enabled, a specific procedure is used to follow the movement.

Following the move

To follow the move of device, all you have to do is call GPSFollowMovement and specify the name of procedure that will be used to manage the move.

Example:

GPSFollowMovement(_GetLocation, 1000)

The code of the procedure can be as follows:

PROCEDURE _GetLocation(MyLocation)

// Update the information about the location
// Latitude and longitude
STC_Latitude = StringBuild("Latitude: %1", MyLocation.Latitude)
STC_Longitude = StringBuild("Longitude: %1", MyLocation.Longitude)

// Speed
IF MyLocation.SpeedValid = True THEN
STC_Speed = StringBuild("Speed: %1 m/s", MyLocation.Speed)
IMG_SPEED_VALIDITY = IMG_OK
ELSE
STC_Speed = "Speed: N/A"
IMG_SPEED_VALIDITY = IMG_NOTOK
END

// Altitude
IF MyLocation.AltitudeValid = True THEN
STC_Altitude = StringBuild("Altitude: %1 m", MyLocation.Altitude)
IMG_ALTITUDE_VALIDITY = IMG_OK
ELSE
STC_Altitude = "Altitude: N/A"
IMG_ALTITUDE_VALIDITY = IMG_NOTOK
END

// Direction
IF MyLocation.DirectionValid = True THEN
STC_Direction = StringBuild("Direction: %1 ° E", MyLocation.Direction)
IMG_DIRECTION_VALIDITY = IMG_OK
ELSE
STC_Direction = "Direction: N/A"
IMG_DIRECTION_VALIDITY = IMG_NOTOK
END

STC_Last_update = StringBuild("Last update on %1 at %2.", ...
DateToString(MyLocation.MeasurementDate.Date), ...
TimeToString(MyLocation.MeasurementDate.Time))
STC_Last_update.Visible = True

In this code, MyLocation is a geoPosition variable. The properties of this type of variable are used to find out the location characteristics.

Ending the use of GPS functions

Depending on the selected settings and on the call frequency, geolocation functions can consume a lot of resources on the device (battery, bandwidth, etc.). GPSEnd must be called when the location functions are no longer used by the application.

When to use each function?

Function	When to use it?	Accuracy	Energy consumption

geoTrackingXXX	Permanent tracking of location changes, even when the application is in the background.	High accuracy, but the frequency of notifications is low and varies depending on the system.	Low
GPSFollowMovement	Permanent tracking of location changes when the application is in the foreground.	Accuracy according to GPSInitParameter.	Consumption according to GPSInitParameter.
GPSDetectPosition	Notification of the proximity of a given location when the application is in the foreground.	Accuracy according to GPSInitParameter.	Consumption according to GPSInitParameter.
GPSGetPosition	Get current location at a specific moment when the application is in the foreground. It may take long, depending on the surroundings (inside a building, cloudy day, etc.).	Accuracy according to GPSInitParameter.	Depends on the number of calls.
GPSLastPosition	Immediately get the last known location of the device.	Low consumption, since it depends on when the last location was actually retrieved. Also depends on GPSInitParameter.	Low consumption.

Functions available according to the platforms

Summary table

The table below presents the different geolocation/GPS functions and the different platforms for which they are currently available (this table can evolve with each version):


Functions			Universal Windows App
geoAzimuth	X	X
geoDistance	X	X	X
Versions 17 and later geoRunApp New in version 17 geoRunApp geoRunApp	X	X
Versions 17 and later geoGetAddress New in version 17 geoGetAddress geoGetAddress	X	X
Versions 26 and later geoGetArea New in version 26 geoGetArea geoGetArea	X	X		X
Versions 21 and later geoTrackingEnable New in version 21 geoTrackingEnable geoTrackingEnable	X	X
Versions 21 and later geoTrackingDisable New in version 21 geoTrackingDisable geoTrackingDisable	X	X
Versions 21 and later geoTrackingStatus New in version 21 geoTrackingStatus geoTrackingStatus	X	X
Versions 21 and later geoTrackingProcedure New in version 21 geoTrackingProcedure geoTrackingProcedure	X	X
GPSStopDetection	X		X
GPSLastPosition	X	X	X	X
GPSDetectPosition	X		X
GPSStatus	X	X	X	X
GPSInfo	X		X
GPSInitParameter	X	X	X
GPSGetPosition	X	X	X	X
GPSFollowMovement	X	X	X	X
GPSEnd	X	X	X

Related Examples:

Cross-platform examples (WINDEV Mobile): WM Geolocation

[ + ] This example explains how to perform proximity searches with geolocation :
- search around me
- search in a city, at a given address, or close to a specific address.
The results are displayed in a looper and in a map with markers.