Set a display's location source

A location program needs to know where the display is. This article covers the three ways a display can get a position. It also covers how one device with GPS can supply every other screen on a vehicle.

Location settings require a Signage - Standard license. A Signage - Basic display has its location source fixed to None and can't serve its position to other displays.

The three modes

Open the display record in Builder and find Location source.

Location source is set per display.

On device works on a phone or tablet with GPS, and on some ruggedized Android devices. It does not work on a Fire TV Stick, an Android TV box or a Windows PC, because none of them has GPS. Those need Poll a server.

Poll a server

The display fetches its position from a URL on the vehicle's local network. Two fields go with it:

• Server URL: an absolute http:// or https:// address. A plain IP address and port on the vehicle's own network is the normal case.

• Poll interval (seconds): between 1 and 3600.

Note: A device serving its position uses port 8772. Read the actual URL off the serving device rather than typing the example shown in Builder's helper text.

This is how a vehicle's existing GPS drives the signage. A chartplotter, a telematics unit, an AIS feed or a vehicle tracker often exposes position over the network already. Point the display straight at it.

Serve a position to other displays

A device with GPS can hand its position to every other screen on board.

1. On the device that has GPS, turn on Serve this position to other displays.

2. Set every other display's location source to Poll a server.

3. Point each one at the serving device's address.

This is the standard pattern for a vehicle. One Android tablet with GPS, mounted where it can see the sky, serves position to four or five Fire TV Sticks driving the passenger screens.

Choose a poll interval

The poll interval decides how fresh the display's idea of its position is, and that directly affects whether triggers fire.

Work out how far the vehicle travels between polls:

Compare that with your trigger radii. A 50 m trigger on a vehicle doing 60 km/h, polling every 10 seconds, is missed most of the time. The display never reports a position inside the circle.

Rule of thumb: the distance traveled between polls should be comfortably less than your smallest trigger radius. Either shorten the interval or widen the radius.

For most vehicle deployments, 2 to 5 seconds works well. A shorter interval costs a little battery and network traffic on the serving device.

Override the setting on the device

You can also set a display's location source on the device itself, in the settings overlay under Location source. This is useful when you're commissioning a vehicle and can't get to Builder.

The overlay shows:

• Mode: Use configured / None / Device GPS / Server URL

• Server URL

• Poll interval (seconds)

• Effective: a readout of what is actually in force right now

Choosing Use configured clears all device overrides and hands control back to Builder. Reload the display to apply location changes.

The Effective readout tells you what's actually in force.

On a device driven by a remote, these fields are read-only. Set them from Builder instead. See Open the on-device settings overlay.

Which setting wins

If the same setting is configured in more than one place, the highest priority wins. From highest to lowest:

1. A launch argument (for managed deployments)

2. The on-device settings overlay

3. A managed configuration (MDM)

4. The display record in Builder

Each value (mode, URL, poll interval) resolves independently, so setting only the poll interval on the device leaves the mode and URL coming from Builder.

Most setups only use Builder, so this rarely matters. See Advanced: command-line options and managed configuration for details.

Good to know

• A display can serve a position it is itself polling from somewhere else, so you can chain the arrangement if the network needs it.

• Before the first position arrives, the screen shows a satellite icon and "Waiting for a location fix." With the mode set to None, it stays blank instead.

• The Effective readout exists so you can see the resolved result without working it out yourself.

FAQ

The screen is stuck on "Waiting for a location fix." What now?

Work through these:

• Mode is None. Set a mode.

• Device GPS with no signal. Indoors, in a garage, or inside a steel hull. Move the device somewhere with sky view.

• Server URL unreachable. Check the address, the port and the network. Try loading the URL in a browser on the same network.

• A very long poll interval. The first fix can take up to one full interval.

Can a Fire TV Stick use a location program?

Yes, but not with its own GPS, because it has none. Point it at a serving device with Poll a server.

Next steps

• Location programs: an overview

• Location programs: triggers
• Open the on-device settings overlay