Learning Center

What your receiver must send to Ditch Assist

The exact output any RTK receiver needs to feed a Ditch Assist control module or DIG module: NMEA GGA at 5 Hz or faster plus VTG, 38,400 baud, RS-232, everything else off. Where it plugs in and how to tell it's working.

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

Ditch Assist® runs on the RTK receiver you already have. The receiver talks to the control module (Full Automation Kit and Guidance Only Kit) or the DIG™ module through the RTK GPS cable, in a standard language of short text messages called NMEA. For the module to understand them, a few settings in the receiver must be exactly right.

Set the receiver up once, the way this page describes, and it works with any of them.

The settings

Write these down and take them to the receiver. The names in the receiver's menus differ by brand; the step-by-step pages for each brand are below the table.

SettingSet it toWhy
Output type and portNMEA 0183, on the receiver's RS-232 serial port (the plug that sends data down a cable)The module reads serial NMEA over RS-232. Nothing else.
Baud rate (how fast the data goes down the cable)38,400The module listens at this speed only. Any other speed reads as garbage.
GGA messageOn, 5 Hz or faster (10 Hz is fine)GGA carries the position, the elevation and the fix. 5 Hz means five positions a second, enough for most installs; 10 Hz suits very fast hydraulics if the receiver can do it. Never below 5 Hz.
VTG messageOnCarries speed and heading. On a receiver that sets a rate for each message, 1 Hz is fine. Where one rate covers every message, use 5 Hz.
Every other messageOff (GSA, GSV, RMC, ZDA, GST and the rest)Extra messages crowd the cable and can slow the positions down.
Talker ID (the two letters at the start of each message)GP, not GN, if the receiver offers the choiceThe module and DIG look for messages that start $GPGGA and $GPVTG.
CorrectionsRTK, from your own base or a networkSet up the way the receiver's maker describes. See Corrections.

In one line, for a card in the cab: RS-232 · 38,400 · GGA 5–10 Hz · VTG on · everything else off · GP.

Step-by-step for your receiver

Where it plugs in

  • Full Automation and Guidance Only Kits: the GPS breakout cable (made for your receiver's connector) plugs into the receiver at one end and into the GPS leg of the main harness at the other. The control module powers the receiver through this cable, so the receiver needs no other power. See Connect all cables.
  • Trimble with a NAV II or NAV III controller: the generic DB9 GPS cable (DB9 is a 9-pin plug) connects to the DB9 serial cable on the Nav controller harness, so the GPS cable runs into the cab. See Trimble and Case IH.
  • DIG: the GPS cable plugs into the DIG main module harness. The DIG supply voltage also goes to the receiver: on a 24 V machine, make sure your receiver can take 24 V. See Mount the DIG ECU and wire it.

How to tell it's working

  1. Switch the control module on and watch Status 2

    Full Automation and Guidance Only Kits only; on DIG, go to step 2. The control module has a light called Status 2. It blinks when any data arrives from the receiver. No blinking means nothing is reaching the module. Blinking means data arrives, but not that the settings are right, and the blink speed isn't the rate: check the rate in the receiver's settings, and the app checks the rest in the next steps. See Read the Status 2 light.

  2. Connect the tablet

    Tap a workflow card on the Home screen and connect, as on Connect the tablet. The window ends with a System Check.

  3. Check the two GPS rows

    GPS Signal turns green and shows how many satellites the receiver sees. GPS Accuracy turns green when the receiver reaches RTK Fixed.

    System Check row: GPS Signal, 22 satellites, with a green tick
    GPS Signal green, with the satellite count: positions are arriving.
    System Check row: GPS Accuracy, RTK Fixed — 0.8 HDOP, with a green tick
    GPS Accuracy green, RTK Fixed: corrections are working too.

    If GPS Signal stays on Waiting for signal..., no positions are reaching the app. Look at Status 2. Not blinking: check the cable and the receiver's output. Blinking: check the baud rate, GGA and VTG, and the rate (see Status 2 blinks, but the app has no GPS). If GPS Accuracy stays amber, the output is fine and the problem is the corrections: see Stuck on Float.

  4. DIG: check the web interface too

    In the DIG web interface, GPS State should read Data Received and GPS Fix should read RTK fix. See The DIG web interface.

Ditch Assist Lite is different

Ditch Assist Lite has no control module and no cable. It runs on an Emlid Reach RS3 or RS4 on the implement, and the tablet reads its position over the receiver's own Wi-Fi network, called its hotspot. That Wi-Fi position output is on by default. If it isn't, the app's Emlid Diagnostics button, at the bottom of Settings, sets everything for you.

Other brands of receiver don't work with Ditch Assist Lite. With another brand, the Guidance Only Kit gives the same guidance through the control module. See The Ditch Assist Lite rover and Set up the receiver for Ditch Assist Lite.

Full Automation Kit: how the parts connect A tractor pulling a scraper with the Full Automation Kit, with numbered markers. 1: an RTK base on a tripod sends corrections to 2: the GPS receiver on a mast on the scraper, which rises and falls with the cutting edge. The receiver is cabled through the GPS breakout harness to 3: the Ditch Assist control module on the scraper tongue. The module talks to 4: the tablet in the cab over its own Wi-Fi, and drives 5: the proportional valve on the tongue, which raises and lowers 6: the lift cylinder. 7: four hoses run to the tractor remotes, one pair on constant flow for the valve and one bypass pair so the lever can still work the implement. 8: the power harness runs straight from the tractor battery, through its fuses, to the module. 12345678Wi-Fi
Full Automation Kit: the receiver on the implement sends its position down the GPS cable to the control module. The module talks to the tablet over its own Wi-Fi and drives the valve.
  1. RTK base. Sends corrections to the receiver for an RTK fix.
  2. GPS receiver. On a mast on the scraper, so it rises and falls with the cutting edge. Its cable runs to the control module.
  3. Control module. On the tongue. Reads the receiver, runs its own Wi-Fi and drives the valve.
  4. Tablet. In the cab, on the module's Wi-Fi. The app works out the target and shows the guidance.
  5. Valve. On the tongue. Raises and lowers the implement when the module tells it to.
  6. Lift cylinder. Moves the cutting edge up and down.
  7. Tractor remotes. Four hoses. One pair feeds the valve on constant flow. The bypass pair lets the tractor lever still move the implement.
  8. Battery and power harness. Straight from the tractor battery, through the harness fuses, to the module.
Ditch Assist Lite: how it connects A dozer with Ditch Assist Lite, with numbered markers. 1: an Emlid Reach RS3 or RS4 on a pole on the blade, the only part on the machine: no control module, no wires to the cab and no valve. 2: the tablet in the cab joins the Reach’s own Wi-Fi hotspot, which has no internet. RTK corrections reach the receiver one of two ways: 3: by LoRa radio from a second Reach set up as a base on a tripod, or 4: from an RTK network over the receiver’s own SIM card. 5: the operator moves the blade, following the arrows on the tablet. Wi-Fi12345
Ditch Assist Lite: one Emlid Reach on the implement. The tablet reads it over the receiver's own Wi-Fi. No module, no cable, no valve: you move the blade.
  1. Emlid Reach RS3 or RS4. On a pole on the blade. The only part on the machine.
  2. Tablet. Joins the Reach's own Wi-Fi hotspot, which has no internet, and shows the guidance.
  3. Reach base. A second Reach on a tripod sends corrections by LoRa radio.
  4. Or an RTK network. Corrections over the receiver's own SIM card. Emlid Corrections over the SIM: RS4 and RS4 Pro only, not in Canada.
  5. You move the blade. Follow the guidance on the tablet.

If it doesn't work

  • Status 2 not blinking: nothing is arriving. The receiver's output is off or on the wrong port, the receiver has no power, or there's a cable or pin problem. Status 2 not blinking.
  • Status 2 blinks slowly, or in bursts with pauses: data is arriving, so the cable and output work. The blink speed doesn't tell you the rate: check that GGA is set to 5 or 10 Hz in the receiver's own settings, and that every message except GGA and VTG is off.
  • The light blinks but the app shows NO GPS: data arrives but a setting is wrong. Check the baud rate (38,400), that GGA and VTG are on, and the rate. Status 2 blinks, but no GPS.
  • Positions arrive but never RTK: a corrections problem, not an output problem. Stuck on Float.

Related

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