With the Precise Point Positioning (PPP) technique, you may accurately determine the coordinates of a static point anywhere in the world without real-time corrections or a base station nearby.
You can do PPP with both Reach RS2 and Reach RS+ devices. To process data from Reach RS+, you can use the NRCAN CSRS-PPP service.
In this guide, we will walk you through the following steps:
Recording RINEX data on Reach.
Exporting raw data from the ReachView 3 app to your mobile device or PC.
Uploading the collected file to a PPP service.
Entering the obtained base coordinates into the ReachView 3 app.
The equipment you need to accomplish the survey:
- Reach receiver
How PPP works
A standalone receiver finds out its position relying on the data obtained from satellites only. Along with raw data, it gets navigation messages with satellite clock offset, the ionospheric and tropospheric corrections, etc. Due to information about these offsets, the receiver may calculate its position with a few meters' accuracy. If there were no navigation data, the accuracy would be much worse.
In RTK and PPK, these offsets might be eliminated since both the base and the rover operate in quite similar conditions.
PPP allows the single receiver to achieve high-level accuracy without the use of corrections from the base station. To calculate the coordinates, PPP uses the same data that is provided by the navigation message but much more accurate. Thereby, the Single receiver might determine its position with a centimeter-level accuracy using only its own raw data and precise ephemerides and clock offsets provided by a PPP service.
The PPP technique is commonly used for determining the absolute base position for further RTK/PPK surveys.
Advantages and disadvantages of using PPP
Post-Processed PPP has both advantages and disadvantages in comparison with PPK technology:
|Only one receiver is needed||The time required to move from Float to a fixed solution|
|The position can be highly accurate determined at any place on the Earth||Most PPP services only allow using Static processing currently|
|The position is determined with absolute accuracy||Most PPP services only allow GPS processing currently|
|Most PPP services only allow multi-frequency processing|
PPP services overview
There are several PPP services available:
- Brazilian IBGE-PPP service, mainly used in South America region, is capable of working with both single-band and multi-band Reach receivers
- AUSPOS 3.0, a PPP service widely used in the Asia-Pacific region, can now process data from Reach RS2 receiver
Before submitting your data to AUSPOS, it's better to delete underscores from the log's name. Otherwise, the service may reject the log.
- Canadian NRCAN CSRS-PPP service can process both single-frequency and multi-frequency logs
In this guide, we will take a closer look at the Canadian NRCAN CSRS-PPP service. However, you can work with other services if more applicable to you.
NRCAN CSRS-PPP service overview
The Canadian Spatial Reference System (CSRS) PPP service is provided by Natural Resources Canada's Canadian Geodetic Survey.
NRCAN CSRS-PPP service uses single or dual-frequency GPS and GLONASS data for solution computation and supports both Static and Kinematic modes.
- Static computation is accomplished with a receiver sitting on one point. As the result of Static mode, you will get the absolutely determined position of this point
- Kinematic mode allows surveying with a moving receiver and provides a path as the solution
Depending on the accuracy level and time that is required to get the solution, the NRCAN CSRS-PPP service can calculate the data in the following modes1:
- FINAL: the accuracy is about 2 cm (0.8 inches), available 13-15 days after the end of the week
- RAPID: the accuracy is about 5 cm (2 inches), available the next day
- ULTRA RAPID: the accuracy is about 15 cm (6 inches), available every 90 minutes
This guide will show you how to process raw data from Reach RS2 recorded in the Static mode. However, with the NRCAN CSRS tool, it is also possible to process the data from a single-band Reach RS/RS+ receiver. With Reach RS/RS+, you will get an accuracy of about 30 cm.
You can learn more about NRCAN CSRS-PPP service on their official site.
Placing the Reach
Place a Reach device precisely above the marked point on the tripod and level it. You can learn more about placing Reach receiver in this tutorial.
Recording RINEX data on Reach
To record logs for PPP, perform the following steps:
Go to the Logging screen in ReachView 3.
Tap Settings in the Raw data section.
Choose the RINEX format and tap Apply.
If you do not know which version of RINEX you need, we recommend using RINEX 3.03. While recording in RINEX format, you can record the UBX file as a backup.
Choose the preset for the used PPP service.
Use the antenna height and enter the measured height to the bottom of the receiver.
Fill in the point's name in the Marker name field.
You can start recording automatically when your receiver is turned on. Check the corresponding field in the settings.
Enable log recording by tapping Start recording.
PPP service requires recording the data for 4 hours at least.
Stop log recording by tapping the End recording button.
You may log the data for up to 24 hours, depending on the accuracy required.
Exporting raw data from ReachView 3
After you finish raw data logging, you may download RINEX data from Reach to your mobile device or PC.
In ReachView 3, go to the Logging tab.
Tap the Download button to export the file.
Submitting data to NRCAN CSRS-PPP service
Click on Sign in button and enter your login and password to access NRCAN CSRS-PPP or create a new account in case you do not have it yet.
In the Email for results field, enter your email address to get the results.
In Processing mode, choose Static.
Choose the datum in which you would like to get the position. In this guide, we will work with the ITRF option.
In the RINEX observation file field, click on the Choose file button and browse for the observation file (raw*.NNO).
Click on the Submit to PPP button to send the file for processing.
NRCAN CSRS-PPP will send the file with the solution to your email address.
NRCAN CSRS-PPP results assessment
After you get the solution report, it might be useful to check how accurate the results are.
In the solution report, look for the Estimated Position. There should be a table with 4 rows:
- The first row contains calculated LLH coordinates in the chosen coordinate system
- The Sigmas row shows an estimated accuracy
- In the A Priori row, there is a few-meter accurate position taken from the RINEX header
- The Estimated - A Priori row displays the accuracy from this position specified in the RINEX header
Setting up obtained base coordinates in ReachView 3
If you need the acquired coordinates to use them as the base position for RTK/PPK, you can now enter the base coordinated into the ReachView 3 app.
In ReachView 3, go to the Base mode tab.
Set the Coordinates entry method to Manual.
Enter the coordinates and specify the antenna height.
If you experience any difficulties during the processing or want to discuss the workflow, start a thread at Community Forum.
1: Tools and Applications: Natural Resources Canada site. URL: https://www.nrcan.gc.ca/maps-tools-publications/tools/geodetic-reference-systems-tools/tools-applications/10925#ppp