Beginning. Basic step-by-step demonstration for: Obtaining Basefile from CORS or local GPS web sites Using basefiles for Differential Correction of Trimble Rover files (.ssf) using Pathfinder Office. overview.
Differential correction compares and corrects your Rover file using a Base file, from a stationary base station receiver (at a known location) for the exact same time as your Rover file.
The first step is to obtain a base file. The most common source are CORS web sites.
Even though we may not use a CORS site, it is important to be familiar with the CORS format…
For local GPS work (within Whatcom County), the Skagit County GPS base station is supperior:
5 second sampling interval (Whidbey CORS is 30 second)
So… use their site instead
Double click to open
Extract to C:/Pfdata/default/base folder
Base file in Base folder…
Now, having downloaded a base file for the correct time period, a Rover file can be corrected using Pathfinder office…
Open Pathfinder office
Add your GPS data
Open Uncorrected Rover file in Pathfinder
Uncorrected Rover file
Differentially correct your Rover file using the corresponding base file
Wait for the Differential Correction window to open… for some reason this seems to take a few minutes.
Use Smart Code and Carrier Phase Processing
Compare corrected and uncorrected files
Open both original Uncorrected rover file
And corrected file for comparison.
Drag a box with zoom tool
Compare the two files…
Both the uncorrected Rover file and the corrected file can be exported to ArcView shapefiles for GIS use and spatial analysis…