1. Post Processing GNSS Data
Transfer data from GPS/GNSS unit to computer using Pathfinder Office
Differentially correct the data using Pathfinder Office
Export the data to ESRI shapefile format
Review and edit the data

2. 1. Transfer data from GNSS unit to computer
Connect the cables and place the GNSS unit in the cradle.
Open Pathfinder Office (PFO).
If you are not prompted to select or create a Project folder, go to File > Projects… and create a New project to hold your data files.
Select Utilities > Data Transfer

3. 1. Transfer data from GNSS to computer
Highlight the Receive tab
Click “Add”, Data File
Select the GNSS rover files (a.k.a. “.SSF” files) that you created
Check that you are using the correct destination
Click “Open”
files are highlighted if they’ve never been transferred

4. 1. Transfer data from GNSS to computer
Click “Transfer All”

5. 1. Transfer data from GNSS to computer
Click “Close”
Verify that files are in the correct directory location on the computer

6. 2. Differential Correction with PFO
Differential correction is the process of removing known errors in GNSS data. Data collected by a base station (or stationary GNSS receiver) is used to correct for known errors in the GPS data. It can improve the accuracy of GNSS positions to sub-meter.
Most errors in GNSS come from effects on timing of the satellite signal. Timing effects can be adjusted if there is a receiver in a known location keeping track of errors. Differential correction (DGPS) uses two receivers: a reference or 'base receiver' that stays at a known location and a mobile 'roving receiver' that is used for the GNSS survey.

7. 2. Differential Correction with PFO
The reference station receives the same GNSS signals as the roving receiver but instead of working like a normal GNSS receiver it attacks the equations backwards.
It figures out what the travel time of the GNSS signals should be, and compares it with what they actually are. The difference is an 'error correction' factor.

8. 2. Differential Correction with PFO
In PFO, choose Utilities > Differential Correction

9. 2. Differential Correction with PFO
Click the button and browse to your .SSF file(s)
Click Next

10. 2. Differential Correction with PFO
Select “Carrier and Code” Processing Type (single base provider if not grayed out)
Click Next

11. 2. Differential Correction with PFO
Choose “Corrected only” for Output Positions
Use Automatic filtering for GPS Filtering (uses the filters applied in TerraSync)
Select “Re-correct real-time positions”
Click “OK” and then “Next”
Select Corrected and Uncorrected when you absolutely need all the data from a remote or important trip. Attributes will allow you to see what was corrected and what was not.
Can change filter settings after data collection
Improves accuracy of real-time corrections (WAAS or Beacon) by overwriting them during post processing

12. 2. Differential Correction with PFO
Choose Base Provider Search, and choose an appropriate station (usually one that is closest or has the highest Integrity Index)
Under Reference Position, choose Use reference location from the base files.
Check the Confirm base data and position before processing box.
Click Next
Base Provider Search - the most automated way. Software goes to the website hosting the data for the base station we selected. It looks at the time of the rover file and figures out which hourly file(s) to pull or whether to pull the daily file. It downloads the file into the Base folder, unzips it, after post processing the rover data, rezips the base station files and leaves them in the Base folder.
Use the "Use reference position from Base File" option in the differential correction wizard.  This in effect puts your COR file in the most current form of NAD83.  That is, NAD83(2011) epoch   THIS IS NOT WHAT WAS TAUGHT IN PREVIOUS YEARS.  THIS IS A SHIFT OF METHODS!!!!!  We have our reasons, but mainly its this.... CORS station are moving so fast, especially in areas of Alaska, HI and CA, it does not pay anymore to "hold" the "WGS84/IGS08" position anymore and shift to the current form of NAD83 during export.  We now want to HOLD the NAD83(2011) epoch position in the COR file.

13. 2. Differential Correction with PFO
Make any changes to the output folder or file naming
Click Start

14. 2. Differential Correction with PFO
When asked to Confirm whether to continue, make sure that the base station was able to provide coverage for the entire time period when data were collected
Click Confirm and Close when differential correction is complete
All processing info is stored in Correct_date.txt file

15. 2. Differential Correction with PFO
Confirm that corrected files (.COR) have been created in your project directory

16. 2. Differential Correction with PFO
TIPS
You can correct multiple SSF files if all were within 100 miles of each other
Use closest base station, CORS or COOP CORS only. Use a current station list (update at least monthly)
Always use “Use reference position from Base File” (puts your COR file in the most current form of NAD83.  That is, NAD83 (2011) epoch 2010
Strive for 100% differential correction
Archive entire GPS Project folder for maximum metadata

17. 3. Exporting the Data to Shapefiles
.COR SHP
Each feature name in the Data Dictionary will be exported as a separate shapefile
In PFO, choose Utilities > Export…

18. 3. Exporting the Data to Shapefiles
Browse to the corrected file(s)
Select output folder
Click New
Name your custom setup
Select Copy of existing setup
Choose ‘Sample ESRI Shapefile’

19. 3. Exporting the Data to Shapefiles
For Type of Data, choose Features – Positions and Attributes, and Export All Features
If Between-feature-logging was used in field, Include Not In Feature Positions will show breadcrumb trail

20. 3. Exporting the Data to Shapefiles
For our purposes, choose option 1 under Output Files
Places all shapefiles in the project’s Export folder

21. 3. Exporting the Data to Shapefiles
For Export Menu Attributes As, choose Attribute Value.
Attributes from your Data Dictionary will automatically be included in the attribute table(s). However, you may select other Generated Attributes to include, as well.

22. 3. Exporting the Data to Shapefiles
Select the correct units for the exported shapefile(s). Generally this is Meters, Sq. meters, and Meters Per Second. You may select these yourself or use the default Current Display Units if they are correct.
Select the desired number of decimal places for your units
Units affect shapefile attributes: Length, Area, Perimeter

23. 3. Exporting the Data to Shapefiles
Choose Filter By GPS Position Info
Data collection settings should have already eliminated data from too high PDOP, etc., but you can repeat those settings here
Uncheck “Uncorrected” and at a minimum check “Postprocessed Code” for types of positions to include
Uncheck Filter By Precision and Include Non-GPS Positions

24. 3. Exporting the Data to Shapefiles
Choose “Use Export Coordinate System”
Click Change and choose appropriate system and datum [NAD83 (CONUS)]
Click OK
Select a Projection File. If ArcGIS installed, coordinate systems folder found in C:\Program Files (x86)\ArcGIS\Desktop10.x\
1) When exporting this NAD83 (2011) epoch 2010 set of features, we want to "do nothing" to the data already in the correct datum. THIS IS A RECENT SHIFT OF METHODS!!!!  Since your COR file from step 3 is already in the correct flavor of NAD83, then you must not double shift the data.  Export selecting NAD83 (Alaska) or NAD83 (CONUS) from the Datum pick list.  Both of these datums do nothing to your data (0,0,0 parameters).  Confirm for yourself by opening up the datum choice under Utilities/Other/Coordinate System Manager.
  4b) Select for Vertical select Geoid 12B for your vertical.  This is the Geoid you must use when using NAD83 (2011) reference. 
2) THIS IS NEW FROM LAST YEAR.    Select from the list of projections, the new coordinate system with the NAD83 (2011) datum tag.  For instance, NAD 1983 (2011) UTM Zone 19N. This projection step above requires a bit of new information for those in ArcGIS 10.x.  New in 10.x is a virtual library of projections. The PRJ's do not exist until you make them a Favorite. Open up the properties of a data frame and select the coordinate system tab. Browse as you would before finding (or searching) for NAD 1983 (2011) UTM Zone 19N . Then press the favorites (star) button.  This makes a PRJ on your computer disk. In windows 7, it resides here C:\Users\yourname\AppData\Roaming\ESRI\Desktop10.x\ArcMap\Coordinate Systems  Lastly, browse to this location from within Pathfinder Office, step 5 and you will then link up a properly exported GPS dataset with the most precise datum tag.

25. 3. Exporting the Data to Shapefiles
Export Tracking Themes only checked if using Tracking Analyst in ArcGIS
Click OK to finish editing Export Properties

26. 3. Exporting the Data to Shapefiles
Click OK

27. 3. Exporting the Data to Shapefiles
Click OK
Check that expected number of features is exported

28. 3. Exporting the Data to Shapefiles
Click OK
Check that expected number of features is exported
When finished, you can click More Details… for a complete report on the success of the export

29. 3. Exporting the Data to Shapefiles
Click OK
Check that expected number of features is exported, and click
Check that shapefile successfully added to Export folder

30. 4. Review and Edit the Data
Do it ASAP, before collecting more data, if at all possible.
Check your memory and your field notes before you edit.
Keep a copy of the original unedited file!
Check features, attributes and spatial pattern.

31. 4. Review and Edit the Data
Point Features: Location
Is the point misplaced relative to other features or an expected pattern?
Check the corrected positions that the point is based on. Check field notes for constellation jumps, PDOP spikes.
Point Features: Theme
Is the feature correct?
Are the attributes correct?

32. 4. Review and Edit the Data
Line and Area Features: Location
Are features in the right location relative to each other?
Are straight lines straight?
Are curves and corners fully spatially defined with enough vertices?
Are there too many vertices?
Do any arcs cross?
Line and Area Features: Theme
Is the feature correct?
Are the attributes correct?

33. 4. Review and Edit the Data
Line and Area Editing