APRS started as an amateur radio service. It stands for Automatic Position Reporting System, an extension of packet (data) radio. Originally it was intended to use GPS data transmitted on a radio frequency to send the location of the transmitter. Think of vehicle tracking. (Both my wife's 4runner and my Avalanche have trackers in them. Kenwood makes both handheld and mobile radio models with APRS features.)
APRS is a simplex service. Data is repeated by high elevation digipeaters which store the received data and then retransmit it on the same channel. I operate the local San Luis Obispo CA digipeater on Tassajera Peak.
Last weekend, I monitored a balloon launch in SE California. The altitude and position was transmitted on APRS. You can read about it and see the pics at
http://n1vg.net/balloon .
One extension of APRS is the transmission of weather data. The program I use on my weather computer is WinAPRS. It uses one serial port to talk to the TNC (terminal node controller, the radio modem) and one to talk to the weather station. It listens to the APRS data sent by other station and plots them on a map. It also transmits my weather data and station location onto the radio network.
That's the original reason I got involved with weather over APRS. I can see the weather conditions at home on the screen on the Kenwood radio in my truck, or on my handheld Kenwood radio wherever I am within a 300 mile radius or so (give or take the vagaries of the APRS network, topography, and radiio propagation).
After the Internet began to explode, amateurs started to gate APRS data onto the Internet. You can see my weather data as gated onto the net at
http://www.findu.com/cgi-bin/wxpage.cgi?KD6DSI .
Which brings us around the corner to the state of weather and APRS and the Internet today. Weather programs like VWS now gate weather data directly on to the Internet APRS servers. It doesn't make it on to the radio network, but anyone monitoring the APRS internet stream, like amateurs, CWOP and the NWS, get to see weather data from all over the US and the world. Some is delivered initially by radio, some directly by internet.
So, to answer your question, the long way around... When I started with WinAprs and VWS several years ago, I had to find a way to split the weather data from my old WM II and then from the VP 2 Plus. Originally I used hardware B&B Data Tap and 2 serial ports on the computer. that was a kluge, and, because of how Davis stations work, wasn't all that stable. It may have had something to do with the fact that I was using a USB to 4 port serial box as well.
You have no idea how pleased I was when you brought out VirtualVP. I use it to feed VWS and WinAPRS (and soon WD) with data from the VP2+. The hardware kluge went away, and everything is more stable.
I'm not very familiar with UIVIEW, but it makes sense. It's easier to interface to outside hardware with a data file than with a COM port, kinda like Anole's weather sticker, and the Southwest Weather Network use data files to generate their graphics.
I'm curious what you run WinAPRS for. Does it connect to a VP (or VirtualVP)?
I don't know a lot about the radio side of APRS. The reason I'm asking is that someone asked for, and I recently added a feature to VPLive to output a WXNOW.txt file which I guess is used as input to another program the radio guys use (uiview?).
Steve