Unable to do differential data correction on data collected using ALTO-G12

“The last time I performed a successful differential correction was a month ago. I have been having trouble with the differential correction ever since. The message it gives me is that there is no data for the base stations. Also, how would I set up the GPS so that it collects raw data?”

In the differential correction screen there is a box for specifying the folder the contains the base files. Make sure that location agrees with where you have placed the downloaded base files

The ALTO-G12 data collector records the raw data by default.

If the base files are not downloaded, the jobs cannot be processed. Did something change on your computer or your network system to prevent the base files from being
downloaded automatically?

Are the firewalls on your PC or an antivirus or antispyware program preventing the ftp access to the NGS CORS site? Please add (or ask your IT person to add)
PCGPS09.EXE to the firewall and antivirus or antyspyware exception lists.

If you are able to access the CORS site outside of PC-GPS 09, you could try the manual procedure for downloading the base files. It is outlined below.
1. You can obtain the CORS Rinex data via non-ftp site through the world wide web. Please use the following address:

2. You will need to download the “RINEX data” and also the “Global Navigation” data (under the non-site specific section) for the day and base station you need.

After downloading and unzipping the data, you will be left with the file extensions: *.17o and *.17n for the 2017 files.
The file prefixes also need to match.
The global ephemeris file has a generic name like: brdcxxx.07n.
Please rename the file prefix to match the *.17o file. For example, if the *.17o file is named: fts11230.17o, then rename the brdc1230.17n file to be: fts11230.17n.

For example PIT1238A.gz is the base file from “Pittsburgh 1” for the first hour (A) of the 238th Julian Day.The unzipped raw correction file is named: PIT1238A.17o.
Rename the ephemeris file brdc1238A.17n to PIT1238A.17n.
Write down the LLA coordinates of the base station.

3. Put the PIT1238A.17o and PIT1238A.17n files in your PCGPS9 folder and point to the folder in the differential correction function.

In the differential correction screen, click the Setup button then select Base Management. Click NEW then add the new base station name and coordinates.

Back in the main differential correction screen, select the base station name.

When you move the rover files into the Selected Jobs section, the matching base files will be highlighted in the Files panel. Then click the Differential button to perform the
differential correction.