A well-placed Reach RS/RS+ module is crucial to achieve good RTK positioning results!

You can place your smartphone near the window in your house and it will obtain GPS coordinates after some time, but for RTK such environment won't be sufficient. For RTK to work there are special requirements for antenna placement that are much more strict that for a standalone GPS.

No obstacles blocking the skyview

Module needs to have a clear skyview 30 degrees above the horizon. There should be no obstacles that could block the view like: buildings, trees, cars, humans, laptops etc.

Examples of bad environments for antenna placement: indoors, urban areas, forest, close to the ground.

Examples of good environments for antenna placement: field, top of the hill, rooftop of a building.

No electronics nearby

Electronic devices may produce RF noise that could affect reception of the GPS signal. Keep all electronics as far as possible from the antenna.