APRS and UiView

APRS and UiView

What do APRS and UiView do?

APRS and UiView are programs that use the packet radio network to allow radio amateurs to communicate data, and to display position information (such as a station’s location) on an on-screen map.

APRS is the acronym for Automatic Position Reporting System and is a program originally developed by Bob Bruninga, WB4APR, who describes it as "a multi-user packet network with a map display". To quote one of the main sources of information about APRS, the system ‘integrates hardware and software to permit amateur radio operators to disseminate data concerning real-time events quickly, and to graphically represent that data on maps displayed on their computers’.

The type of information communicated using APRS includes information about the station (whether it is fixed, mobile, acting as a digipeater, etc.), short text-based messages, and weather information. If either APRS or UiView are being operated from a moving vehicle, suitably equipped with a GPS receiver, then the software can also transmit information about the vehicles’ direction and speed and plot these on a map.

Unlike traditional packet operation, which uses one-to-one communication between stations, APRS and UiView use unconnected packets to disseminate information on a one-to-all basis. As with traditional packet stations, APRS and UiView stations use digipeaters to disseminate their transmissions. However, they do not have to specify a digipeater path and can use generic digipeater paths so that prior knowledge of the packet network is not required. APRS requires the use of a TNC (Terminal Node Controller), whereas UiView can be used either with a TNC or software TNC emulation such as the AGWPE packet engine.

Besides WB4APR's DOS version, there are also versions for other platforms - Windows, Mac. etc. In the USA, "APRS" is a registered trademark of WB4APR. UI-View32 is an APRS application for 32 bit Windows and was written by the late Roger barker (G4IDE).

Comparatively, APRS is primarily used in the United States and UiView in the UK and Europe, although APRS and UiView stations will be found all around the world.

Some features of UiView

UiView, like APRS, provides a map display (See Figure 1). Based on the position information - in the form of latitude and longitude - sent in the packet stream UiView plots the position of the transmitting station onto a map. If the station is moving (i.e. a mobile) then the station can be tracked. It is possible to load any number of maps into UiView, either country maps, continent maps or world maps. Figure 1 shows a map of England and Wales. The filled in squares that appear on the map represent other maps that I have available that overlap the map that is currently displayed. Clicking on these squares changes the map display.

Figure 1 is a relatively uncluttered map - the program had been running less than a minute at this point. There are a number of features to notice.


First, stations can select their own icon - mine (partially obscured) happens to be a church (because I live next door to one!). The lorry icon (call sign G6ZNW-7) is a typical mobile symbol. Clicking on the icon will bring up a small information box (Figure 2), which gives information about the mobile station (typically, time, speed and direction). I have often thought that this would be an excellent facility (if irritating) for the police to use to catch speeding motorists!


Second, stations running weather stations use the ‘WX’ symbol. Clicking on the icon will display an information box that contains all the weather information being transmitted. Quite useful if you are traveling to a specific area, but beware as some amateur weather stations can be very unreliable!


Third, as UiView uses unconnected packets for communication, if there aren’t any didipeaters, or nodes, to connect to, communication stops. One way round this is to use the Internet to assist communication. Consequently, there are now many ‘Igates’ around the world that relay UiView traffic across the Internet. The station identifying itself as MB7UHR is an example of an Igate. Some Igates operate 24 hours a day, seven days a week, others are more intermittent. But their function is the same – to relay UiView traffic. Consequently, if an Igate is operating locally it is quite possible to see traffic appearing (if you have a world map displayed) from all over the world.


Fourth, it is possible to load overlays onto the map. These might be locations of Igates, BBS nodes, satellite gateways, DX clusters, etc. Figure 4 shows part of a map with A DX Cluster overlay. The little boxes with a ‘DX’ inside them are the DX Cluster locations. Clicking the DX icon brings up an information box which shows the frequencies on which the DX Cluster operates.

Fifth, one can also add ‘Objects’ to the map, which will be transmitted along with the location information. In Figure 5 I have added the object ‘DEMO’ to my packet transmission. DEMO will now appear on everyone’s maps. Clicking on the DEMO item will reveal a comment, which in this case simply says ‘UiVIEW Demonstration’. Imagine, though if your Club is having a car boot sale, or an evening lecture, it would be possible to transmit a ‘Club Event’ object, together with details of the event sent as a comment. A useful way of letting people know what is going on at your local Club.


Some applications of UiView

So, what is the point of UiView? It’s great for tracking, it can provide a useful weather facility and it provides a facility to let people know what is going on at your local Club. (In the USA, APRS is increasingly being used as part of their emergency communications resource.) A very useful facility is messaging. Usually, in order to send someone a message over Packet, you have to make a connection to their system. You then either chat "live" with them or leave a message in their PMS. Whichever you do, the exchange of information is made using AX25 connected mode. This is not so with UiView. Although the message may be directed to a particular call sign, anyone can receive the message.

Figure 6 shows the messages screen. You can see that I am part way through sending a message. The first part of the message has already been sent (the software automatically sends a line of text either when a line-end is reached or when a carriage return is used) and I am in the middle of the next line of text. Ignore the other lines of text in the message screen – they are other stations chatting or sending packet acknowledgements.


UI-View(32) messages are very casual compared to ‘connected packet’ messaging services. You can send another UI-View(32) user a message at any time, simply by putting their call sign in the "To" box, inputting some text and pressing <return>. The message is sent as a UI frame and the acknowledgement is also by a UI frame. Connected mode is never used for UI-View(32) messages.

Any message text addressed to you will be saved in files named according to the sender's call sign if "Options", "Save To File" is checked.

UI-View(32) supports two formats of message - it's own format and also APRS format. Although UI-View(32) format has some advantages over APRS format, users of other APRS software will not be able to receive UI-View(32) format messages. If you operate in an environment where most users aren't using UI-View(32), then you should use APRS format.

Personally, I have found that I can send and receive messages over no more than about five nodes (or five jumps from one node to another). Clearly, with the use of Igates it is possible to send and receive messages around the world, although I have only made it to Holland – once! But, it is possible to jump many more nodes, depending on the number of nodes that are connected and amount of traffic that is flowing.

It is also possible to send emails through UIView. One has to know the email address of the intended recipient, and according to our current regulations, the recipient must be an amateur. The emails are sent through UiView, tended to get digipeated all around the world and end up in your email in-box. This isn’t a facility I have used very much. But, for testing purposes, a local amateur and I sent each other an email this way. I received his email 2 days later, via Singapore. He never received my email! Not, then the quickest or most reliable of services, but interesting nevertheless.

The UiView software is very simple to use, although there are increasingly more complicated facilities if one chooses to use them. The Help file is very explicit, albeit a little authoritarian at times. The software is available from: http://welcome.to/uiview . This site also provides numerous maps and add-on software. However, UiView itself is no longer supported and is unlikely to be further developed, although there are numerous sites which provide help if it is required. There is a small voluntary registration fee that is donated to the Cancer Research charity.

UiView and APRS have been growing in popularity for some years now. It certainly has its uses and if nothing else it can provide an alternative mode for local natter nets. Try it, and see what you think.

Thanks to Andrew (G8GNI) for contributing this article.

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