Learning Center

Use a Bluetooth GPS receiver

Connect an RTK receiver to the tablet over Bluetooth to survey or walk a route without the machine. What a Bluetooth receiver can and can't do in the app, how to pair and connect it, and its limits.

  • Full Automation Kit
  • Guidance Only Kit
  • DIG™ Kit

A Bluetooth GPS receiver lets the tablet record a survey without the machine: walk a trench centreline before the excavator gets there, or survey a run from a pickup. The tablet talks to the receiver by Bluetooth (the same short-range radio a phone uses for earbuds) and reads its position.

It's a GPS source only. It never drives the blade: Start on the Grade screen stays grey until a control module, the DIG™ module or the simulator is connected.

What it can and can't do

Works with Bluetooth GPS

Surveying a route or field (the RTK Filter applies as usual), designing from that survey, importing data, and checking position and fix in the GPS Info window.

Needs a module or the simulator

Automatic grading (Start), the live position marker on the grading profile chart, the hydraulic test, generating and following contours (a control module or an activated Ditch Assist Lite receiver), and the LiDAR & Mapping unlock (a control module, DIG module or activated Ditch Assist Lite receiver).

Bluetooth GPS is in the Ditch Assist mode only. In Ditch Assist Lite the connect window offers Emlid Reach and Simulate, nothing else. It's also only in a workflow card's connect window, not in Pre-Flight Checks.

Before you start

Time: about 5 minutes the first time, a few seconds after that.

  • An RTK receiver that sends NMEA GGA (and VTG) over Bluetooth, with its RTK corrections working. An Emlid Reach set up by the app as Rover or Lite Rover already does: its second position output is Bluetooth NMEA (see Configure an Emlid Reach).
  • The app in the Ditch Assist mode, not Ditch Assist Lite (see Choose the mode)
  • No other phone or app connected to the receiver over Bluetooth (for example Emlid Flow)

First, pair the receiver with the tablet

Pairing introduces the receiver to the tablet. You do it once per receiver, in the tablet's own Settings app, not in Ditch Assist.

  1. Switch the receiver on

  2. Open the tablet's Settings app

    The app with a gear icon (see The Settings app).

  3. Open Bluetooth

    On a Samsung tablet it's under Connections. Make sure Bluetooth is switched on.

  4. Tap the receiver's name in the list of devices

    If you don't see it, check the receiver is switched on and close by.

  5. If the tablet asks to pair, tap Pair

  6. Go back to the Ditch Assist app

    Press Back until the app is on screen (see The Back button).

Connect in the app

Tap a workflow card

On the Home screen, tap the card for the job, for example Ditching, the first card at the top left. A window opens with connect choices.

The Home screen with nine workflow cards; Ditching is the first card at the top left
  1. Ditching. Any workflow card works the same way.

Tap Bluetooth GPS

It's the third button in the window, under the green Connect and the white Simulate, with a Bluetooth symbol and blue words. A window called Bluetooth GPS opens.

The Ditching connect window: Connect to Controller, with a green Connect button, then Simulate, Bluetooth GPS and Manual Options
  1. Bluetooth GPS. Third button, with the Bluetooth symbol.

The first time: tap Allow

The first time, Android asks two questions, one after the other. One asks whether Ditch Assist may find and connect to nearby devices: tap Allow, the top choice.

The app needs both answers to be yes. If you tap Don't allow, it can't see the receiver and shows Bluetooth permissions denied. Go to Android Settings to grant access. (see If it doesn't work).

Android asks: Allow Ditch Assist to find, connect to, and determine the relative position of nearby devices? with Allow and Don't allow
  1. Allow. Needed once, so the app can find your receiver.

The first time: tap While using the app

The other question asks whether Ditch Assist may use the tablet's location (Android ties Bluetooth searching to location). Tap While using the app, the first of the three choices. If the app already has location access, this question doesn't appear.

Android asks: Allow Ditch Assist to access this device's location? with Precise and Approximate, then While using the app, Only this time and Don't allow
  1. While using the app. The first of the three choices.

Wait for your receiver to appear

The window reads Select a paired GNSS receiver. Pair new devices in Android Settings. A paired receiver appears in the list straight away. The words Scanning... and a small spinning circle show while the app keeps looking for other Bluetooth devices nearby; that's normal.

The list can also show other Bluetooth devices nearby, such as phones. Find your receiver by its name. The one you used last is at the top, marked Last used.

The Bluetooth GPS window: Select a paired GNSS receiver. Pair new devices in Android Settings. A spinning circle and Scanning... in the middle, Cancel at the bottom right
  1. Bluetooth GPS. The window's name. Paired receivers are listed under the line of grey text.
  2. Scanning.... Here no receiver is paired yet, so the list is empty.

Tap Connect beside your receiver

Each receiver in the list shows its name, its address, a small tag for the kind of Bluetooth (SPP classic, BLE low energy, or Dual) and a blue Connect on the right. Tap Connect beside yours. The app uses classic Bluetooth where the receiver offers it, because it's the more reliable link.

The Bluetooth GPS window listing one device, RTK Receiver, with its address, a BLE tag and a blue Connect on the right
  1. The receiver's name and Bluetooth type. Here a test receiver called RTK Receiver, on BLE. Yours shows its own name.
  2. Connect. On the right of the receiver's row.

You should see the System Check turn green

The window runs its System Check. Wait until its bottom row, GPS Accuracy, shows RTK Fixed with a green tick before you survey. Then tap Continue.

System Check row: GPS Accuracy, RTK Fixed — 0.8 HDOP, with a green tick
GPS Accuracy: RTK Fixed, green. Ready to survey.

Limits

  • No valve control, ever. Bluetooth GPS can't grade, and it can't take over the GPS source while you're grading on a control module.
  • Range: keep the receiver close to the tablet. If the link drops, the app tries to reconnect by itself, waiting a little longer each time (2, 4, 8 seconds and so on, up to 30), for up to 10 tries. After that, connect again from a workflow card.
  • Same fix rules: with the RTK Filter on (it is, unless someone turned it off), the survey only records points at RTK Fixed. See How RTK works.
  • No Wi-Fi rows: the GPS Info window shows no Wi-Fi Signal or Link Speed for a Bluetooth source, because it doesn't use the tablet's Wi-Fi. It does show Correction Age when the receiver reports it.

If it doesn't work

  • Your receiver never appears; the window stays on Scanning...: it isn't paired, or it's off or out of range. Tap Cancel, pair it (see First, pair the receiver), check it's switched on and close by, then tap Bluetooth GPS again. In app version 1.5.4 the word Scanning... stays on for as long as the window is open, even when nothing is found.
  • Bluetooth permissions denied. Give the app the two permissions in Android:
    1. Open the tablet's Settings app (see The Settings app).
    2. Tap Apps.
    3. Tap Ditch Assist.
    4. Tap Permissions.
    5. Allow Nearby devices, and Location.
  • Failed to connect to … The receiver may be connected to another phone or app over Bluetooth (for example Emlid Flow). Disconnect it there and try again; switch the receiver off and on if needed.
  • Connected, but NO GPS: the receiver isn't sending NMEA over Bluetooth. Turn on its Bluetooth NMEA output (GGA and VTG). No GPS in the app.
  • Start is grey on the Grade screen: expected with Bluetooth. Connect the control module or DIG to grade.
  • Stuck on FLOAT: Stuck on Float.

Related

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