Thanks to the rebirth of interest in the radio amateur localization system APRS, I decided to try this system myself and compare it with the TrackMe program. The decisive criteria in the comparison were several factors: the price for which I can operate the system, the complexity of the system, practical usability both from the point of view of me, as an object broadcasting its location, and from the point of view of the user locating my location on his computer, accuracy and the ability to broadcast the location permanently, without interruptions.
I will briefly describe both systems and the results of the comparison. To clarify: I am only concerned with a comparison in the field of localization, not for other possible uses. I do not consider myself an expert in this field, it is possible that some parts will not be agreed with. However, I have no intention of arguing with him and I will only be happy if he corrects me in any possible misinterpretation.
APRS
The APRS system does not need to be explained in detail, it is certainly known to all radio amateurs. It is a purely amateur radio system. The principle consists in determining our position with a GPS receiver, the data is processed by a modem, e.g. TinyTrak and sent to the transceiver, which transmits data to the diginode at a frequency of 144.800 MHz.
APRS má však, na rozdiel od TrackMe, širšie využitie, z rádia možno napr. posielať správy inému účastníkovi siete, na APRS sú vysielané meteorologické údaje. K „povinnej“ výbave je teda nutné mať GPS receiver, modem a TRX. V tom najjednoduchšom prípade to bude mať hodnotu cca 300-500 Eur. GPS receiver však potrebujeme v oboch systémoch, nejakú tu ručnú alebo mobilnú FM rádiostanicu na 2m vlastní však skoro každý rádioamatér, takže beriem do úvahy ako cenu iba modem. Spomínaný typ TinyTrak stojí okolo 70 USD, modem so vstavaným GPS stojí cca 135 USD. Samozrejme, na trhu je veľa APRS modemov za rôzne ceny s rôznou výbavou a schopnosťou programovania. Do modemu totiž treba naprogramovať našu call, prípadne meno alebo iné naše údaje.
Another set is also possible: GPS, notebook, Baycom modem and transceiver. However, lugging a laptop around just for APRS seems a bit far-fetched. On the other hand, in this composition we can also receive and broadcast other interesting information to the network. We load this whole assembly into the car, tune in the right frequency, attach the antenna to the roof and we can go out into the world.
As long as we are within range of the APRS diginode, it will receive the packets sent by us and send them out to the world via both radio and Internet networks. On the receiving side, a program must be installed on the computer, most often UIview32. With it, we can download data either from diginod or from the Internet. In the first case, in addition to a computer (and, of course, access to diginode), we also need an RX or TRX at 144.800 MHz, a modem, or a sound card. In the second case, we are able to receive APRS information directly from the Internet, from special APRS servers, without the need to use another device. It can be seen that building a setup for APRS broadcasting is not a difficult thing. A suitable modem may be a problem, but it is not an insurmountable problem. However, carrying this whole set in the car when we go on a trip can become a burden after a while, because of which we start making up various excuses as to why we are not locateable right now.
The settings of the conditions for sending the position are also different from the type of modem used. In the best case, we can set the broadcast depending on the time, i.e. e.g. every minute, then sending if we travel a greater distance than the set one, or if we change the direction of our journey by a greater angle than the set one, i.e. e.g. 30 degrees.
In Slovakia, unlike the surrounding countries, we are faced with another, really big and currently insurmountable problem. And that is APRS diginodes. To date, there are exactly two. OM3KII-2 in Bratislava and Trnava OM3KTR-2. It is said that it is also planned in the east, I believe that it will be built, and that there will be more of them. It would certainly make for a long and passionate discussion (and which I certainly do not want to provoke with this post) as to why such a situation exists in Slovakia. It is a thought-provoking situation. Is it because of the lack of young, computer-savvy radio amateurs? Or due to the fact that, similar to what we experienced with Packet radio, we only have what enthusiasts pour their own money and effort into? Or is there another reason? I don't know…
It is, of course, possible to use diginodes from abroad near the borders. In flat terrain, with a decent antenna, we can count on a range of 30-50 km to a remote diginode. If the diginode were placed on a suitable dimension, e.g. Veľká Javorina, on the entire route from Bratislava to Považská Bystrica, it would be possible to transfer our data to the APRS network without any problems.
In today's situation, however, on the road, e.g. to Prešov, I lose the Trnava diginode signal somewhere halfway to Nitra. And the end... Nothing on the entire route to Prešov, maybe somewhere behind the Tatra mountains, short-term weak signals from the Polish side. During operation, if the diginode does not receive our high-quality signal at the input, there are failures (due to the fact that the diginode in principle does not confirm the reception of our data) and a state where some point is not recorded. If we cannot send (or the diginode cannot receive) several points in this way, the route displayed at the receiver is distorted, sometimes even misleading.
All in all, it follows that this system is currently unusable in Slovakia, except for the area around Trnava and Bratislava and the route between these cities. However, we can use it with great advantage anywhere abroad, with the exception of the former Soviet states. Western Europe in particular is littered with diginodes.
From the point of view of the recipient of our location, the lack of diginodes is not such a problem. As I mentioned above, it is also possible to receive location data from the Internet. The most used, but not the only, program for displaying APRS stations is the UIview32 program. The program is intended directly for receiving (but also broadcasting) APRS information. It is pleasant to work with, but it has, in my opinion, one fundamental shortcoming, and that is the maps. There are few calibrated maps for APRS for this program, they are often poorly calibrated. The disadvantage is also the impossibility of adequately zooming the area we are interested in. However, it is also very often used to display stations directly from the Internet browser at the address http://APRS.fi , which uses Google Maps.
I personally tried another system. However, I do not want to describe it in more detail, because it was labeled as a system that completely suppresses the meaning of radio amateur APRS and has nothing to do with radio amateurs. To some extent this is true. But as a radio amateur has, for example, from Žarnovica broadcast your position to the APRS system? I (as part of testing) replaced the modem and TRX with a mobile phone and radio transmission with GPRS transmission. I used a PDA that directly contains a GPS receiver. The GPS data was processed in the PDA by the AGWTracker Pocket program, I sent the data via bluetooth to a mobile phone that was connected via GPRS to the Internet gate, which in turn transferred my data to the APRS system. An hour of broadcasting positions costs about 20 cents, no position is lost for sure and I am absolutely not dependent on the reach of the diginode. The signal of mobile operators is practically on 100% of our routes, it is lost exceptionally and even in that case nothing is lost, because the data is stored in the memory in the event of signal loss and after it is restored, it is poured into the network. So the whole equipment is a PDA and a mobile phone, while I use the PDA for navigation at the same time - I share data from the GPS for the iGO program and for AGWTracker Pocket. This system is also suitable for hiking, the PDA is light, I can have a hiking map in it, the battery lasts about 6 hours with the display on, much more when it is off. However, due to the almost certain resistance of orthodox radio amateurs, I will not describe this system in more detail and I myself do not use it even except for tests. The disadvantage is that the aprs.fi server does not display stations that send data to the network via iGate.
I will now go back to the original radio transmission.
The advantages of this system are the following:
- is intended exclusively for the radio amateur community
- the costs for the establishment are not high, for the operation itself almost zero
- transmissions abroad are also free
- the possibility of transmissions of data other than location data Among the disadvantages I would include:
- single purpose modem required
- the need to wear a relatively large and energy-intensive set
- diginode range required
- quite a lot of unprocessed data (dropouts) with poor signal quality
- lack of high-quality maps for the imaging programTrackMe
Luis Espinosa programmed and offers a freely distributable version of TrackMe. This program is also intended for localization and can also partially send SMS or e-mail. It already follows from this that it is necessary to have access to the Internet for its activity. It doesn't have to be immediate, because the program can store data in itself, and when we return from the trip, we can dump it on the Internet. However, we lose the possibility of "live" localization. The program is therefore freeware and is intended for the general public.
The principle is as follows: the data from the GPS receiver is processed by the program in the PDA, via bluetooth it sends the data to the mobile phone, which in turn sends the data via GPRS to the Internet, usually to our server, where the data is recorded in the MySql database. At the same time, the data is also exported to the server in .kml format. The recipient opens our website, where he runs a php script that reads this data and, in cooperation with Google map, displays either our route from the database or the "live" position from the .kml file. You can open my page for lighting http://www.depe.sk/TrackMe . After opening, you will see a world map. If you select "Trip" in the right column, you can choose from several test trips that I have taken. After selecting the route, click on "Show". Two routes are marked "...taking a long time to load". The two routes are each about 1,200 km long and each contains about 3,500 recorded crossing points, so the opening takes a long time, sometimes even 2-3 minutes, maybe even more. The other routes are up to 30 km long and therefore open relatively quickly. After opening, you can zoom the map as you wish, clicking on a transition point will display all the data related to this point.
Clicking "Live Tracking On" in the right column will take you to live tracking (only if I'm moving, of course, otherwise you'll see my last location). If I am sending data, you can see my exact location and the route taken. The refresh interval can be set from 10 to 99 seconds. For those with a fast internet connection, I recommend 10 seconds, for slow connections 30-60 seconds. It is also possible to set the "zoomlevel", i.e. the size of the zoom. After setting, the map will be displayed in this zoom level during the next Reload. It is possible to display the map in Satellite or Hybrid mode, but these settings only last until the next Reload, and then the Map mode starts again. Finally, give it a try.
I have actually already described the necessary technical equipment: it is optimal to own a PDA, "personal digital assistant", in which the Windows Mobile 5 or 6 operating system is installed and which is directly equipped with a GPS receiver. It must have bluetooth connectivity. The mobile phone should also have bluetooth and the possibility of connecting to the Internet via GPRS. When connecting, you must use EDGE, not CSD connection! CSD would be quite expensive for us, because the price is based on the length of the connection time and not on the amount of transferred data, as is the case with EDGE. With EDGE, the price depends on how we set up the program and how often we send data. I reached max. the value at the extreme setting is about 400 kB per hour, which cost me about 0.6 Euro. In practice, however, we do not use such an extreme setting. I specifically use the EASY card from T-Mobile, there is no need to activate any special program.
There are a large number of PDAs on our market that meet our conditions at various prices. The cheapest ones start somewhere around 150 Euros, but you can buy them for 600 Euros. However, investing in a PDA is, in my opinion, a good investment, because a PDA is actually a small computer that you can use for a variety of purposes: from navigation, through games, a music or movie player, various text applications, a diary to a racing diary, or DX cluster. It's hard to get a mobile phone that doesn't have the required parameters, so I don't even count this one. So that's all from the technical equipment.
The software consists of installing and configuring the TrackMe program in the PDA and installing the server application on our web server. The web server probably requires its own web space, because I am not sure if free web servers offer the possibility of a MySql database. However, a large number of Internet providers offer free connection, usually around 50 MB of web space, and I know from my own experience that 90% of people do not use this web space. The application page is then displayed on your website, similar to what I described above. I also installed the PortSplitter program on my PDA. This program can connect multiple programs to the GPS at the same time - so I use GPS at the same time for travel navigation and for TrackMe.
I am at a loss to express the level of complexity now. For a person who moves around computers and the Internet, this is no problem. However, for an ordinary Internet user, this can be a problem that cannot be overcome by his own efforts, so he will be forced to ask for help. In any case, a functional result can be achieved. Operation is very simple from the user's point of view - you need to connect the PDA to a mobile phone using bluetooth and connect the phone to the Internet. After that, just start the correctly configured TrackMe program and go out into the world. The configuration consists in specifying the server to which we connect, the username and password, and setting the parameters for when the data should be sent (time, distance, change of direction). It is also possible to set different conditions for data transfer. If you are not using another program, you lock the PDA, which also turns off the display and significantly saves the battery. It is even easier for the user who is viewing your location on the website.
Your location is sent with the accuracy of the GPS receiver, usually a few meters. It is displayed with the same accuracy on Google Maps on your pages. The interval can be much shorter than with APRS, so tracing is significantly more detailed. However, the biggest advantage is that not a single point of the route is lost, and internet connection failures are rather the exception, unless we are moving in deep valleys of high mountains. But even then, after the signal is rediscovered, all untransmitted, but postponed waypoints will be transmitted.
So I'll recap the benefits first:
- low weight of equipment
- low energy demand
- easy physical installation in the car
- easy user operation both on the transmitting and receiving side
- significantly greater accuracy with respect to transmission intervals
- significantly greater accuracy due to the fact that no route point is dropped
- very cheap operation of GPRS transmissions (we transmit very little data) Disadvantages include:
- Necessity of knowledge of working with PDA and website programming
- PDA price
- possibility to use only in Slovakia, prices abroad are high
Conclusion
It is difficult for me to comment on which system is better, more advantageous. As a radio amateur, I lean towards APRS, but without diginodes, APRS is useless to me. In addition, I am a bit discouraged by the fact that APRS is easily accessible only to radio amateurs and the UIview32 program itself (maps).
On the other hand, the main disadvantage of TrackMe is the need to pay, albeit small, fees for GPRS transmission and, due to the high prices of data roaming, the inability to use this system abroad. But if you've read this post to the end, you'll have some idea of the localization options yourself, and it's up to you which of these systems you choose.Dusan, om2adp