Focus On Water Division
Nebraska Department of Environmental Quality
Standard Operating Procedure

Water Quality Division
Water Quality Assessment Section - GW

Standard Operating Procedure Number GW-092
Title: Processing GPS Rover Files Into Latitude/Longitude Data
Written Date: September 1, 2000
Approved Date:


Purpose: To correct data files.

Equipment/Materials Needed:

1. Computer with Pathfinder Office software and Internet access
2. Software key
3. Data set of rover files (*.ssf files)

Procedures:

1. Plug software key into serial port of computer, if necessary.
2. Using Windows Explorer (or similar file management program) create Project directory in C:\Pfdata directory (Limit name to 8 characters, e.g. Sample).
3. Create the following directories in C:\Pfdata\Sample directory.
3.1. Backup
3.2. Export
3.3. Base
4. Copy/transfer the rover *.ssf files to C:\Pfdata\Sample directory.

Download Base Station Files

1. Open Bullet Proof FTP (The following procedures are based on the Bullet Proof FTP software. Other FTP client software can be used).
2. Select “Site Manager” from the Main menu.
3. Select or Create site “GPS Base Station Files”.
4. If the specifics for this Internet site have not been created, they are as follows:
4.1. Site Address: ftp.sso.state.ne.us
4.2. Port: 21
4.3. Login: anonymous
4.4. Initial Local Directory: user’s choice (preferably the directory C:\Pfdata\Sample\base).
4.5. Initial Remote Directory: gpsdata/gisland/rinex (The data from the Grand Island Base Station can be used over most of the state. If working with data files from the far west or east portions of the state, the Scottsbluff and Lincoln Base Station data can be used).
5. Select “Connect” button.
6. Select the directory for the date of your rover files. You will need to know the times the rover files were collected.
7. Highlight the hourly base station data files (in *.zip format) needed. (Use the Control button on the keyboard to select multiple files).
8. Select the button “Queue for Download” which has a down-pointing arrow on it.
9. Select the “Go” button to begin download of files.
10. Quit Bullet Proof FTP after all files are downloaded.

Data Correction

1. Open PathFinder Office.
2. Select or Create a New Project Name.
3. Select Batch Processor from Utilities Menu.
4. Check Differential Correction and Export; select Next button.
5. Select Browse to choose the *.SSF files; select Next button.
6. Differential Correction: Select “Use Selected Base Files” (Make sure the directory selected is where the downloaded base station files are located).
7. Use Reference Position - From Base Files.
8. Select the “Settings” button.
8.1. The Rover Files are located in C:\Pfdata\Test
8.2. For Base Files, select Browse button.
8.3. C:\Pfdata\Test\base
8.4. Select all the *.zip files in the C:\Pfdata\Test\base directory
8.5. ***The Window “Confirm Selected Base Files” shows which rover files match up with which base files. All rover files must have a match, otherwise Patfhfinder will not work.
8.6. Select OK.
8.7. The Window “Reference Position” appears and press OK.
8.8. The window “Confirm Reference Position Adjustments” appears; press OK.
8.9. Select the directory for the Corrected Files (*.cor).
8.10. Processing is “Smart Code and Carrier Phase Processing”.
8.11. Select “Close” button.
9. Select Next button.
9.1. Export Setup is “Sample Arc/Info (PC) Generate Setup”.
9.2. Export Folder is C:\Pfdata\Test\Export.
10. Select Next button.
11. Select Run button.
12. Quit Batch Processor.
13. Quit Pathfinder Office.
14. The output file “posnpts.pts” lists the longitude and latitude for each *.ssf file. The order in which the *.ssf files were read is identified from the file “exp0000a.txt” (where 0000 is the date, e.g. 0425 is April 25th). The posnpts.pts and exp0000a.txt files are both text files and are located in C:/Pfdata/Test/export.