In the mid 1990’s the first dual constellation receiver boars appeared on the market that integrated single-frequency GPS plus GLONASS signals. Now we explained that in order to generate coordinates one must be viewing 4 satellites, but to truly generate "Good Coordinates" you would like to see 6 satellites. Finally to have the "best" accuracy you need to receive signals from a minimum of eight satellites. Well, there are times during the day when it is impossible to get eight GPS satellites in view, even on a flat job site! Now, add in some trees, a few buildings—you could be lucky to receive 4 or 5 GPS satellites. What does that do to your accuracy, if you’re able to keep working at all? Ultimately, when you invest in a positioning solution, whether for a surveying crew or for stake less 3-D grading, you want “uptime” not “downtime,” and that uptime must be accurate.
Therefore, the one overwhelming advantage to GPS and GLONASS integral systems is this — the integration provides access to 33 percent more satellites than ordinary GPS. That’s because GPS with GLONASS has the ability to track not only both frequencies of all 24 GPS satellites, it can also receive the signals from the 9 GLONASS positioning satellites (with another 6 GLONASS satellites scheduled for launch this year). The accessibility to more satellites directly relates to the precision obtained. A satellite availability comparison shows that at all times the Dilution of Precisions are lower numbers when GLONASS satellite information is included with GPS satellite positioning information, in comparison to GPS satellite positioning information alone.
