How to Force GPS Capture

Overview

In some cases, GPS data may not be captured automatically, especially when the interview is conducted indoors or when the device has a weak GPS signal.

This article explains how to require GPS data before the survey can be completed. If GPS coordinates have not been captured, the surveyor will not be able to continue until valid GPS data is available.

This setup includes:

1. Adding GPS validation logic to Advanced Scripts.

2. Creating a validation question that checks whether GPS data was captured.

Step 1: Add the GPS Logic to Advanced Scripts

Open the survey's Advanced Scripts section and add the following code:

function OnGPSUpdated(inLocation)
{
    if ((SubjectGPSLocation == null || !SubjectGPSLocation.IsValid) && inLocation != null && inLocation.IsValid)
    {
        SubjectGPSLocation = CreateCoords(inLocation.Latitude, inLocation.Longitude);
    }
}

function myLocationDataValid()
{
    var retVal = false;

    retVal = SubjectGPSLocation.IsValid;

    if (!retVal)
    {
        var currentLocation = GetGPSLocation();

        if (currentLocation != null)
        {
            SubjectGPSLocation = CreateCoords(currentLocation.Latitude, currentLocation.Longitude);
        }

        retVal = SubjectGPSLocation.IsValid;

        if (!retVal)
        {
            OpenGPS();
        }
    }

    return retVal;
}

This script checks whether a valid GPS location already exists. If not, it attempts to retrieve the current GPS location. If GPS data is still unavailable, it opens the GPS screen so the surveyor can capture it.

Step 2: Create a GPS Validation Question

Create an empty question near the end of the survey. This question will display whether GPS data has been captured and will prevent the survey from continuing until valid GPS data exists.

Start Script

Add the following code to the question's Start Script:

SetTextFormat(CurrQues, myLocationDataValid());

Question Text

Use the following text:

Was GPS captured until now: {0}

End of the survey. This question includes a validation check to make sure GPS location information was captured.

You can change the wording of the question text if needed. Keep {0} in the text, as it is used to display the current GPS validation result.

Step 3: Add the Validation Rule

Create a validation rule on the GPS validation question.

Condition

!myLocationDataValid()

Message

Enter the message you want to display when GPS data has not yet been captured.

For example:

GPS data has not been captured yet. Please wait for a valid GPS location before continuing.

This validation prevents the surveyor from continuing until myLocationDataValid() returns true.

Optional: Add a GPS Confirmation Question

You can add another empty question immediately after the validation question to confirm that the GPS coordinates were successfully recorded.

Start Script

SetTextFormat(CurrQues, SubjectGPSLocation.Longitude, SubjectGPSLocation.Latitude);

Question Text

GPS coordinates were recorded:

Long: {0}
Lat: {1}

You can now safely finish the survey.

Summary

This setup ensures that the survey cannot be completed until valid GPS coordinates are captured. It is useful for surveys where location verification is required, especially in environments where GPS capture may be delayed or unreliable.