A high-accuracy GNSS receiver can be used with any survey with no prior configuration, but typically some metadata collection and accuracy rules are defined in the survey before use. To learn more, see Prepare for high-accuracy data collection.
Take the following steps to use a high-accuracy receiver with the Survey123 field app:
- Choose a receiver.
- Configure your receiver.
- Connect your receiver to your device.
- Configure Survey123 to use the receiver.
Choose a receiver
Survey123 can use the GPS that's built into your device, or you can add an external GPS receiver to obtain high-accuracy data. There are many GPS receivers available; however, not all of them work directly with Survey123. To use a GPS receiver with Survey123, the receiver must support the output of NMEA sentences.
To improve the accuracy of your positions, consider using a GPS receiver that supports differential corrections. If you are using an iOS device, you must also choose one of the GPS receivers supported on iOS. While Esri doesn't publish a list of supported GPS receivers for Android or Windows, a list of receivers used in testing on Android and Windows is provided.
Most high-accuracy GPS receivers support the NMEA sentences that Survey123 uses; however, it's recommended that you check whether your receiver supports these NMEA sentences in the receiver's user manual before you try to connect it to Survey123.
NMEA 0183 is the data specification standard that Survey123 uses to communicate with GPS receivers. NMEA messages contain lines of data called sentences. Survey123 derives GPS information such as latitude, longitude, height, and fix type by reading specific sentences in NMEA messages.
Survey123 supports NMEA 4.00 and 4.10. It can read the following NMEA sentences:
- GGA: Time, position, and fix-related data
- GSA: GNSS DOP and active satellites
- GSV: GNSS satellites in view
- RMC: Recommended minimum specific GNSS data
- VTG: Course over ground and ground speed
- GST: GNSS pseudorange error statistics
If Survey123 receives GST sentences, which contain accuracy information for a particular coordinate, it uses them to determine accuracy. By default, the horizontal and vertical accuracy numbers are specified in root mean square (RMS). The level of confidence using RMS is 63 percent to 68 percent for horizontal accuracy, and 68 percent for vertical accuracy.
If you need to report the 95 percent confidence interval for horizontal or vertical accuracy, you can calculate this in your survey by multiplying the reported accuracies by a conversion factor. For more information, see Report the 95 percent confidence interval.
If Survey123 doesn't receive a GST sentence from a GPS receiver but does receive a GSA sentence, Survey123 estimates accuracy using horizontal dilution of precision (HDOP) and vertical dilution of precision (VDOP). The estimated horizontal accuracy is calculated by multiplying HDOP by 4.7, and the estimated vertical accuracy is calculated by multiplying VDOP by 4.7.
To improve the accuracy of your positions, consider using a GPS receiver that supports differential corrections. Differential correction technology further improves accuracy by using reference stations, which are also known as base stations. A reference station is another GPS receiver that is established on a known location. The reference station estimates its location based on satellite signals and compares this estimated position to the known position. The difference between these positions is applied to the estimated GPS position calculated by your GPS receiver, also called the rover, to get a more accurate position. Your receiver must be located within a certain distance of the reference station for differential corrections to occur. Differential corrections can be applied in real time in the field or when postprocessing data in the office.
Differential corrections can be provided by public or commercial sources. One of the most widely used and publicly accessible real-time correction sources is the Satellite-based Augmentation System (SBAS), which is also commonly referred to as the Wide Area Augmentation System (WAAS) in the United States. It is free to use SBAS, but your GPS receiver must support it. Using commercial correction services typically requires a subscription and may also require purchasing a particular type of GPS receiver that can receive these correction signals. See the Differential GPS Explained article in ArcUser magazine for more information.
GPS receivers supported on iOS
To directly connect a Bluetooth receiver with an iOS device, the receiver must be part of the MFi program as well as support the output of NMEA sentences. The following receivers can be used directly with Survey123 on supported iOS devices.
To determine the version of firmware your GPS receiver uses, pair your receiver with your device, open your device's General > About settings, and tap the name of your paired receiver.
- Bad Elf GNSS Surveyor and GPS Pro+, GPS Pro, and GPS for Lightning Connector
The GNSS Surveyor and GPS Pro+ require firmware version 2.1.40 or later. The GPS Pro requires firmware version 2.0.90 or later. The GPS for Lightning Connector requires firmware version 1.0.24 or later.
- Eos Arrow Lite, Arrow 100, Arrow 200, and Arrow Gold—Firmware version 2.0.251 or later
- Garmin GLO, Garmin GLO 2—Firmware version 3.00 or later
- Geneq SxBlue II and SxBlue III—Firmware version 2.0.251 or later
- Leica Zeno GG04 plus—Processor board firmware version 1.0.20 or later
GPS receivers tested on Android and Windows
Survey123 works with any receiver supported on Android or Windows that outputs NMEA 0183 sentences. While the development team doesn't certify any device, the following is a list of devices it has used:
This is not a comprehensive list of all devices that work with Survey123.
- Bad Elf GNSS Surveyor, GPS Pro, and GPS Pro+
- Eos Arrow Lite, Arrow 100, Arrow 200, and Arrow Gold
- Garmin GLO¹, Garmin GLO 2¹
- Geneq SxBlue II and SxBlue III²
- Leica GG03¹, GG04, and Zeno 20¹
- Trimble R1, R2, R8s¹, and R10¹
For the Trimble R1 receiver on Windows, Survey123 can't access differential GPS fixes with RTX. However, Survey123 can identify the location with autonomous GPS fixes, as well as SBAS corrected and local base station corrected locations via NTRIP.
For the Trimble R2 receiver on Windows, Survey123 can't access locations with RTX or local base station corrected locations via NTRIP. Survey123 can only access autonomous GPS fixes and SBAS corrected locations.
The development team has had issues pairing the Trimble R10 with Samsung Galaxy S5 and S7 devices.
¹Android only; ²Windows only
Configure your receiver
Not all receivers that support the output of NMEA sentences are configured to do so out of the box. Refer to the device's user manual for instructions on how to configure it to output NMEA sentences.
Connect your receiver to your device
Survey123 supports receivers integrated into devices as well as external receivers connected via Bluetooth. If your receiver is integrated into the device, proceed to the next section. If you are using an external receiver, follow these steps to connect it to your device:
- Verify that your GPS receiver is compatible with Survey123.
- Turn on your receiver and place it near your device or computer.
Go to your device's Bluetooth settings and view the available devices. Wait for your receiver's name to appear in the list.
If your Bluetooth receiver doesn't appear in the list, make sure it isn't connected to another device.
- To disconnect your receiver from an iOS device, in the device's Bluetooth settings, tap the information icon next to the receiver, tap Forget This Device, and tap Forget Device.
- To disconnect your receiver from an Android device, in the device's Bluetooth settings, tap the settings icon next to the receiver, and tap Unpair or Forget.
- To disconnect a Bluetooth receiver from a Windows device, in the device's Bluetooth settings, tap the receiver's name, tap Remove device, and tap Yes.
- Tap the receiver's name to pair it with your device.
Configure Survey123 to use the receiver
You can configure more than one receiver for use with Survey123. For each receiver, you can customize the name, alerts, antenna height, and altitude options. These settings are saved on your device for subsequent use.
- Open Survey123.
- On the main menu, choose Settings.
- On the settings menu, choose Location.
- Choose Add Provider.
- From the list of external receivers, choose the receiver you want to connect to.
- The default location provider type is External receiver of type Bluetooth. The External receivers list will display all receivers that are already connected to your device but are not yet added to Survey123. On desktop devices, you also have the opportunity to browse USB-connected devices. To change the type of devices that are listed, disable device discovery, check or uncheck the type of external receivers to search, and then reenable discovery.
- You can also connect to receivers that are available on a network. Choose Network connection and enter the host name and port. Choose Add.
Once a receiver is selected, it connects and you are taken to its Settings page. You can check or modify the receivers settings here or press the back arrow to return to the Location page, where you can browse other configured providers, add a new provider, or leave the Survey123 settings.
Your receiver is now providing locations to Survey123.