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 a receiver
- Connect a receiver to a device
- Configure Survey123 to use a receiver
Choose a receiver
Survey123 can use the GPS that's built into a 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 positions, consider using a GPS receiver that supports differential corrections. If you are using an iOS device, you must also use 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.
Tip:
Most high-accuracy GPS receivers support the NMEA sentences that Survey123 uses; however, it's recommended that you check whether the receiver supports these NMEA sentences in the receiver's user manual before you try to connect it to Survey123.
NMEA support
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 that 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 the survey by multiplying the reported accuracies by a conversion factor. For more information, see Report the 95 percent confidence interval.
Estimated accuracy
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.
Differential corrections
To improve the accuracy of 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 the GPS receiver, also called the rover, to get a more accurate position. The 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 the 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. For more information, see Differential GPS Explained.
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.
Tip:
To determine the version of firmware a GPS receiver uses, pair the receiver with a device, open the device's General > About settings, and tap the name of the paired receiver.
- Bad Elf Flex,
Bad Elf Flex Mini, Bad Elf GNSS Surveyor, GPS Pro+, GPS Pro, and GPS for Lightning Connector
GNSS Surveyor and GPS Pro+ require firmware version 2.1.40 or later. GPS Pro requires firmware version 2.0.90 or later. 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 and GLO 2
GLO requires firmware version 3.00 or later and GLO 2 requires firmware version 2.1 or later.
Accuracy values delivered by the Garmin GLO do not update at the same rate as location information. Accuracy on this receiver is calculated from PDOP and HDOP values and these are outputted only once on start-up of the receiver.
- Geneq SxBlue II and SxBlue III—Firmware version 2.0.251 or later.
- Juniper Systems Geode
- Leica Zeno GG04 plus—Processor board firmware version 1.0.20 or later.
- Trimble R1,
R2, R10 Model 2, R12, R12i, and Catalyst DA2
You must use Trimble Mobile Manager to configure your receiver. Do not use the Trimble GNSS Status app.
GPS receivers tested on Android and Windows
Survey123 works with any receiver supported on Android or Windows that outputs NMEA 0183 sentences. While Esri doesn't certify any device, the following is a list of devices that have been used:
Caution:
This is not a comprehensive list of all devices that work with Survey123.
- Bad Elf Flex, Bad Elf Flex Mini, Bad Elf GNSS Surveyor, GPS Pro+, and GPS Pro
- Eos Arrow Lite, Arrow 100, Arrow 200, and Arrow Gold
- Garmin GLO¹, Garmin GLO 2¹
Accuracy values delivered by the Garmin GLO do not update at the same rate as location information. Accuracy on this receiver is calculated from PDOP and HDOP values and these are outputted only once on start-up of the receiver.
- Geneq SxBlue II and SxBlue III²
- Juniper Systems Geode
- Leica GG03¹, GG04, and Zeno 20¹
- Trimble R1,
R2, R8s¹, R10¹, R12¹, R12i¹ and Catalyst DA2¹
On Windows, Trimble GNSS Status is required to receive corrected positions with a Trimble R1 or R2. On Android, Trimble Mobile Manager is required to configure a receiver.
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.
Issues have occurred when pairing the Trimble R10 with Samsung Galaxy S5 and S7 devices.
¹ Android only
² Windows only
Configure a 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 a receiver to a device
Survey123 supports receivers integrated into devices as well as external receivers connected via Bluetooth. If the 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 a device:
- Verify that the GPS receiver is compatible with Survey123.
The receiver must support the output of NMEA sentences and be configured to do so. See Choose a receiver and Configure a receiver. These instructions must be completed before connecting the receiver to Survey123.
- Turn on the receiver and place it near a device or computer.
Go to the Bluetooth settings and view the available devices. Wait for the receiver's name to appear in the list.
Tip:
If the Bluetooth receiver doesn't appear in the list, ensure that it isn't connected to another device.
- To disconnect a receiver from an iOS device, in the device's Bluetooth settings, tap the information button next to the receiver, tap Forget This Device, and tap Forget Device.
- To disconnect a receiver from an Android device, in the device's Bluetooth settings, tap the settings button next to the receiver, and tap Unpair or Forget.
- To disconnect a 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 the device.
Configure Survey123 to use a 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 the 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 the 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, wait for the location sensor to be discovered, then choose Add. Alternatively, the host name and port can be entered manually.
- If you have a NMEA log file on the device, you can connect to this to playback the recorded NMEA messages. Choose Add from File, select the log file. 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.
Note:
Grid-based transformations are not supported in Survey123.Record a NMEA log file for playback
When you go out into the field, you can capture a NMEA log that you can then replay when you are back in the office. This is great for doing demonstrations to colleagues whilst indoors, or for working with tech support to troubleshoot unexpected GNSS behavior.
- Go to the GNSS location status page.
- Switch to the Debug tab.
- Tap the record button.
Whilst you are recording, you can carry on using the other features of the app. When you are finished moving around, come back to the Debug tab and stop recording.
You can also create an NMEA log when using the integrated location provider. Positions from the device are translated into RMC and GGA sentences so that they can be read and used in the same way as logs from an external receiver.
Recorded NMEA log files are saved to the following location:
- Windows—C:\Users\<username>\ArcGIS\My Survey123\Logs
- iOS—Survey123/Documents/ArcGIS/My Surveys123/Logs
- Android—Android/data/com.esri.survey123/files/ArcGIS/My Survey123/Logs
You can capture NMEA logs in this same way in AppStudio Player with the GNSS Discover sample, Survey123, or QuickCapture. Logs captured in any of the apps can be used in any other of these apps.