DGPS at night

Does anyone have any ideas as to why DGPS position information may become less accurate at night.

What settings can be tweaked to fix this, such as masking elevation etc.

Could it be you’re picking up more than 1 LF reference station? Another possibility, receiving the ground wave signal plus an NVIS or skywave of the same transmission.

Thanks for the reply, you sound like an expert.

My question is probably a bit vague.

Its a Kongsberg system we are using. Professional help has been requested, but I’ve seen it on other vessels in the past where at sunset/ night time the DGPS position information becomes unreliable. Vessel is operating near the Equator.

[QUOTE=follow40;137558]Thanks for the reply, you sound like an expert.[/QUOTE]

Far from it and I wish an expert would chime in. The lower frequencies can do strange things at twilight.(grey line propagation) Atmospheric noise also increases in the summer and lower latitudes. At MF, I’ve heard reverberation in signals caused from receiving them short and long path skywave simultaneously.

A few of us can still remember manually locking on to a loran A or C signal on a CRT. The skywave trails were visible on the CRT.

Could be scintillation, a result of high sunspot activity and shows up strongest at dusk and overnght. Good website at the Jet Propulsion Lab. Could be military providers evoking security for their homeland.

Are you talking IALA data?
its free why complain

It is very common for DGPS to be less accurate during sunset and sunrise, especially around the equator.
It has something to with the breaking of the sunlight in the atmosfere. As light is a wave just like a radio signal it can interfere with radio signals under the right circumstances.

Some receivers are more affected by this than others but they are all affected in some way.

Do you lose the signal from the GPS satellites or the Differential signal?