Product specifications

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Product B’s specification of sub-meter rms, you can see the first Product A would
offer better performance.
To properly evaluate one receiver against another statically, they should be using
identical correction input (from an external source) and also share the same antenna
using a power splitter (equipped with appropriate DC-blocking of the receivers and a
bias-T to externally power the antenna). With this type of setup, the errors in the
system are identical with the exception of receiver noise.
Although this is a comparison of the GPS performance qualities of a receiver, it
excludes other performance merits of a GPS engine. The dynamic ability of a
receiver should be compared in a similar way with the test subjects sharing the same
antenna. Unless a receiver is moving, its software filters are not stressed in a similar
manner to the final product application. When testing dynamically, a much more
accurate reference would need to be used, such as an RTK system so that a ‘truth’
position per epoch is available.
Further, there are other performance merits of a GPS engine, such as its ability to
maintain a lock on GPS and SBAS satellites. In this case, the same GPS antenna
should be shared between the receiver test subjects. For the sake of comparing the
tracking availability of one receiver to another, no accurate ‘truth’ system is
required, unless performance testing is also to be analyzed. Again, an RTK system
would be required, however, it’s questionable how its performance will fair with
environments where there are numerous obstructions, such as foliage. Other
methods of providing a truth reference may need to be provided through observation
times on surveyed monuments or traversing well-known routes.
If you require assistance in developing a test setup or procedure for evaluating the
Crescent, please contact Hemisphere GPS.