kristinemlarson
commented
6 months ago Note: when i saw "good to 10 meters" please remember that won't be good enough for most Fresnel zone maps. You want the location of the station to be as good as the photo's geo-coordinates.
From a gnssrefl user:
_I noticed that gnssirinput requires longitude, latitude, and height coordinates as inputs. My question pertains to the impact of using approximate coordinates on the accuracy of GNSS-IR reflectivity estimation. Specifically, I am curious to know if providing approximate coordinates significantly affects the accuracy of the estimated reflectivity height.
The main use of this information is to make a refraction correction when running gnssir. Otherwise, the values are only used when you want to make Fresnel zone maps. So the coordinates should be good - but they don't have to be crazy good. They certainly do not need to be carrier phase quality positions. Within ten meters should be fine. The refraction correction is most important when your site is high above the water, i.e. > 30 meters. It doesn't really matter for snow and soil moisture people.
The refraction correction generally impacts accuracy - not precision - of reflector height. The default is to make a refraction correction - and I discourage people from turning it off.
There is a secondary use of the station height - it is used by subdaily for putting the final evenly sampled spline series into an orthometric system. So if your goal is to have super accurate "heights" then yes, the input to gnss_input is important. This option is a work in progress however.