Data Acquisition Based on GPS Location

Direct YouTube link: https://youtu.be/LHE10MsqvZI


In Simcenter Testlab Signature, data acquisition can be triggered based on Global Positioning Satellite (GPS) location and speed.

This article describes how this is done:
1. Getting Started
2. Simcenter Testlab Signature
   2.1 Channel Setup
   2.2 Measure
   2.3 Tracking Setup
3. Multiple GPS Conditions
   3.1 Virtual Channel Definition
   3.2 Tracking Setup with Virtual Channel

1. Getting Started

First the GPS antenna needs to be attached to the SCADAS hardware as shown in Figure 1.

Figure 1: Simcenter SCADAS XS with GPS antenna
 

The GPS antenna is a single connection.  All SCADAS XS hardware have a built-in GPS.  SCADAS Mobile units do not have a GPS, while SCADAS Recorders have one.

The GPS receiver needs to be in view of the open sky to receive satellite positioning data.  It cannot be indoors.  In a vehicle, it can be on the dashboard with just glass between it and the sky.

Using the internal GPS built into the Simcenter SCADAS, data acquisition can be triggered using:

• GPS location - Using latitude and longitude co-ordinates in angle (4 digits of precision after decimal preferred)
• GPS speed - Speed at which the SCADAS is traveling, typically in kilometers per hour (kph or km/h)

The latitude and longitude angles on the earth are shown in Figure 2 below:

Figure 2: GPS triggers can be based on either latitude or longitude angular positions

Using Google Earth or Google maps, the degree position of the latitude or longitude trigger can be determined.  An angle with at least four digits after the decimal is typically used.

Displaying the latitude or longitude in a numerical display and driving to a location can also help in determining the values to use.

With the SCADAS hardware turned on, the GPS antenna plugged in, start Simcenter Testlab Signature.

2. Simcenter Testlab Signature

The GPS is enabled in the software in two different locations:

2.1 Channel Setup

In "Channel Setup" worksheet, set "Clock sync:" to "GPS" in the upper right corner as shown in Figure 3:
 
If satellites are in view, the status of the sync should be green.

2.2 Measure 

In the “Measure” worksheet, click on the “More…” button as shown in Figure 4.
 
Turn on the checkbox for "Measure GPS Data" and press the "Close" button.

The status area on the right hand side should sage "GPS" and "3D Fix". If there is no fix, make sure the GPS receiver has a clear view to the sky above.

2.3 Tracking Setup

Triggers can now be defined based on GPS speed or location.  This is done in the Tracking Setup worksheet as shown in Figure 5:
 

Multiple conditions can be used as a trigger. For example, the trigger can be set so that data is acquired when the GPS speed is above 19 kilometers per hour, but below 21 kilometers per hour.

3.1 Virtual Channel Definition

This is done using Virtual Channels in the Channel Setup of Simcenter Testlab Signature. This virtual channel will have a value of "1" when the desired trigger condition is met, and a value of "0" at all other times.

For example, the virtual channel could be a value of "1" if the GPS speed is greater than 19 kph. The virtual channel formula would be "GREATER(gps: Speed;19) to do this. "GPS: Speed" refers to the GPS channel. (Note: There is no space between the ":" and "Speed". The space was added to prevent some browsers from showing emoticons)

Create a virtual channel by selecting the "Virtual Channels" in the upper right corner of the Channel Setup worksheet (Figure 6).
 

Figure 6: In the upper right corner of Channel Setup Worksheet, select "Virtual Channels" from the pulldown menu.

Enter formulas in the Virtual Channels editor to create the desired trigger (Figure 7).
 

Figure 7: Virtual channels with logic commands will produce either a zero or a one when the GPS co-ordinates and GPS speeds are within the desired areas.

For example, to trigger when speed is between 19 and 21 kilometers per hour, enter the following:

• V2 - GREATER(gps: Speed;19)
• V3 - SMALLER(gps: Speed;21)
• V4 - AND(V2;V3)

If both channels V2 and V3 are true (and each has a value of 1), then V4 will also have a value of 1. V4 can be used for a trigger.

Alternatively, both GPS location and speed can be used.  For example to take data on a specific road surface at a precise speed:

• V1 - GREATER(gps: Latitude;40.3013)
• V2 - GREATER(gps: Speed;19)
• V3 - SMALLER(gps: Speed;21)
• V4 - AND(V2;V3)
• V5 - AND(V1;V4)

Setting a GPS trigger based on both location and speed could be useful to ensure that data is taken over a specific road surface at an exact speed (Figure 8).
 

Figure 8: GPS location and speed triggers ensure data is acquired on a specific road surface at a uniform speed

3.2 Tracking Setup with Virtual Channel

In the "Tracking Setup" worksheet, use the "Triggered Start" or "Triggered Stop" to set triggers based on the Virtual logic channels (Figure 9).
 

Figure 9: In the Tracking Setup worksheet, the triggered start can be set based on the logic virtual channels.

The value of the logic channel varies between 0 and 1.  Any value between 0 and 1 will work for the trigger.


Questions? Post a reply, or contact charles.rice@siemens.com.

 

Simcenter Testlab Acquisition Tips

• Index of Testing Knowledge Articles
• Simcenter Testlab Data Acquisition Tips
• Simcenter Testlab Signature
• Cool Channel Setup tricks for Triaxial Accelerometers
• Data Acquisition Based on GPS Location
• How to calculate a VECTOR SUM
• Tips and tricks for acquiring torsional orders
• Capturing Transient Events in Simcenter Testlab
• Copy Channel Setup from One Project to Another?
• View Channel Setup from Desktop Navigator!
• Tips and tricks for acquiring torsional orders
• CAN Bus Measurements
• No more tach! OBDII for engine speed
• Cool channel setup tricks for triaxial accelerometers
• GPS triggered data acquisition
• Viewing data in Google Earth
• Record Raw CANBUS Data and Decode Offline!
• Single Plane Balancing in Simcenter Testlab
• Measuring strain gauges in Simcenter Testlab
• Correcting a bad calibration factor
• Simcenter Testlab Calibration