You have two or four major types of GPS systems. Real-time correction of
pusedorange or carrier calculation and post process of the same. The real-time
GPS stuff needs radios as well as the benchmark system. In the case of
standardized RTCM correction against a first quality benchmark where the rover
is in local proximity of 10 kilometers, kinematic accuracy's of .5 to 1.5 are
very typical for well tuned systems. You can access in may areas a US Coast
Guard RTMS AM broadcast or buy a subscription to a RTCM service.
For carrier corrected GPS in real-time the radios are a must as will be the
matching benchmark receiver and correction generator. As the carrier
correction data is verbose more sophisticated radio modems are needed. Care
and tuning also govern how well the system pinpoints positions but deca-meter
accuracy's (10 - 20 cm) are readily attained.
You can also post process the GPS logs by simple data logging at the rovers and
benchmark. The RTCM real-time accuracy is duplicated by the RINEX post
processing standard. In many cases where latency of the real-time RTCM
correction is a issue, RINEX will give better accuracy. There is national
RINEX system available via the CORS sites. These RINEX compatible CORS sites
can be accessed via the net.
Any of these systems are disrupted by simple satellite blockage. They can
provide very jittery and unreliable navigation due to multi-path error found in
all urban canyons. GPS systems integrated to interial hardware can smooth out
many of the canyon effects. They are not perfect.
MidNight Mapper
aka Neil
7/14/99
William Gutierrez wrote:
> Hello...!
>
> I'm deciding which is the appropriate GPS receiver to collect data in a
> city. It has to be compatible with MI in order to create points directly in
> MI. If you have any idea of prices or sites that I could visit, please, let
> me know.
> Any comment or help would be appreciated
>
> TIA
>
> William G.
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