there are at least two relativistic effects involved in gps timings - http://www.aapt.org/doorway/tgru/articles/ashbyarticle.pdf http://www.aapt.org/doorway/tgr

there are at least two relativistic effects involved in gps timings - http://www.aapt.org/doorway/tgru/articles/ashbyarticle.pdf http://www.aapt.org/doorway/tgru/articles/ashbyarticle.pdf - but they would not be solved if the satellites were in geosynchronous orbit as the earth itself does not have a single non-accelerating reference frame.