[OSM-talk] military vs consumer GPS and the equator

[simon at mungewell.org]

>
> I was under the impression that you still need those reference
> stations for doing surveys, because of those atmospheric conditions
> you mention.
>

A reference station is really just a receiver that doesn't move and is
well surveyed in.

You can use a reference station if you have one close (say less than
20km), use a virtual reference network (normally a bit pricey) or use a
second unit (aka 'base') as the reference station.

When you are using a pair of receivers your system is really just giving
you the deltas in position, which is why you would place the base above a
survey marker in the pavement/sidewalk.

You can even get pretty good results using just an L1 receiver, say 5cm
with good antenna/reception but will have a much more limited baseline
length.

Simon.