I've had hands-on experience using Tru-Traffic TS/PP with a few different types of GPS receivers, and they're not equal. The short advice is to get one that uses both of the following
If your GPS receiver has a serial (RS-232) cable but your computer has only a USB port, you can still use a USB-to-serial adaptor to plug it into a USB port. These adaptors come with software drivers for serial port emulation.
Garmin has some GPS receivers (e.g., the eTrex Legend C, Legend Cx, Vista C, Vista Cx, etc.) with USB cable and a purely USB interface — no serial emulation available. These require additional software to work with Tru-Traffic TS/PP. One software product, Franson's GpsGate allows GPS-enabled applications that accept NMEA input over a serial port (for example, Tru-Traffic TS/PP) to work with Garmin USB-based GPS receivers (using the Garmin USB protocol) by emulating a virtual serial port. It looks like it costs about US$10/computer. A Tru-Traffic TS/PP user has confirmed that it works fine with the software in NMEA mode. Unfortunately, as far as he can tell, it does not emulate the serial port with the Garmin (proprietary) protocol. This means you can connect the GPS to the laptop out in the field and run just fine, but you cannot, as far as we can tell, take the GPS solo out in the field, use it to record intersection coordinates ("waypoints") and trip logs ("tracks"), then download to the computer when you return to the office.
Two chips sets seem especially promising for use in urban canyons and under tree canopies: the SiRFstarIII and SiRFstarIIe/LP, which uses SiRFXTrac. A number of manufacturers offer GPS receivers based on these chip sets, including Garmin, HAiCOM, Holux, Magellan, Pharos, and TomTom. If you search for SiRFstarIII, you should get a number of hits. I have personal experience with the HAiCOM and Pharos (see below), but not with the rest of these. Several users have been very pleased with the accuracy and reliability of the SiRFstarIII-based Pharos iGPS-500, which came with Microsoft Streets & Trips 2007 and 2008. Unfortunately, it no longer comes with Microsoft Streets & Trips 2009, so to get it, you have to purchase directly from the manufacturer or from another vendor.
We must distinguish a humble GPS Receiver from full fledged GPS Navigation System, the sort of device you'd put in your car to find addresses and give you driving directions. Most simple GPS Receivers will provide "raw" geographic position & time information, either to a file or, better, over a live connection (a serial port, a Bluetooth connection, a USB port, etc.), which Tru-Traffic TS/PP needs for its trip analysis. Most of the full fledged GPS Navigation System do not provide "raw" geographic position & time information, providing instead travel routes and driving directions, as they're intended for strictly navigational purposes. As such, most GPS Navigation System are not suitable for use with Tru-Traffic TS/PP for travel time & delay studies. If the specifications for your device mention NMEA 0183 somewhere, then it will almost certainly work with Tru-Traffic for travel time & delay studies. If it does not mention NMEA 0183, then it may or may not work with Tru-Traffic TS/PP, and you'll need to investigate further to decide which is the case.
Despite my limited experience, I get the impression that anymore, it's hard to go wrong as long as the GPS receiver specifies NMEA 0183 somewhere. If you have experience with any of these units and can offer feedback that may benefit others, please let me know, and I'll post it here.
Some GPS receivers can record their own trip logs ("tracks"), which gives you options:
I've used the original Earthmate (which had only a RS-232 serial connection). This worked well and had the additional advantage that it gave an update every second, as opposed to every 2 seconds as all the NMEA GPS receiver I've tried. It was relatively inexpensive and came with its own mapping software. Disadvantages are that it could work only when connected to a computer, not as a standalone unit, and its battery life was very short, making the power cable connector a virtual necessity. Have you noticed I've been using the past tense here? A perhaps bigger disadvantage is that it's no longer available except through eBay (probably used). I give it a qualified recommendation.
DeLorme has replaced the old Earthmate with a new one, the Earthmate® GPS LT-20 (and GPS LT-40), which has a USB connection and is NMEA-0183 compliant. This new one does work as a standalone unit and is supposed to have a longer battery life. Although the new one does not have an RS-232 serial interface, one can download "COM Port Emulation Drivers for the USB Earthmate GPS Receiver" from the DeLorme web site. I've confirmed that these allow it to operate with Tru-Traffic TS/PP, but starting with version 6.0.0.42. At the time of this writing, there's a bug in their NMEA-0183 compliance, and ver. 6.0.0.42 works around this bug. If your computer doesn't have a USB port, DeLorme also sells a serial interface cable.
While my basic testing with the DeLorme Earthmate® GPS LT-20 shows that it works with Tru-Traffic TS/PP, a user in Houston has used it much more extensively and reports reliability problems when recording trip logs – frequent bad readings and signal interruption messages from Tru-Traffic TS/PP.
I've been quite happy with DeLorme's Blue Logger. It's probably the one I'm using most often these days, since the wireless setup is so simple.
One user has reported being quite happy using the Deluo USB GPS for Laptop with Tru-Traffic TS/PP. Costing about $55, it's one of the least expensive ones you can buy and supports NMEA through the USB port, so it takes its power from your laptop. Unfortunately, the Deluo USB GPS for Laptop specifications do not indicate that it's using a chipset such as the SiRFstarIII and SiRFstarIIe/LP, which use SiRFXTrac. This isn't critical, and it may not even matter, but without such a chipset, it's likely to have difficulty maintaining a fix in low-signal conditions, such as urban canyons or under tree canopies.
I've tried 4 different Garmin GPS receivers,
They all worked fairly well with Tru-Traffic TS/PP. The basic eTrex is relatively inexpensive (but requires separate purchase of the data cable), and they all have the advantages that they have a fairly long battery life and can also work as a standalone unit — they don't have to be connected to the laptop. I give them a qualified recommendation. I have to qualify it because a number of users, including me, have encountered these bouts where the software and the GPS receiver suddenly stop communicating altogether for no obvious reason -- the Diagnostics page just stops scrolling. None of us know what's the pattern. Usually, when this happens, we can break it loose from whatever stupor it's in by restarting the GPS receiver and/or the software. Often toggling the communications protocol (from Garmin to NMEA 0183, or from NMEA 0183 to Garmin) in both the GPS receiver and the software does the trick. Sometimes we have to reboot. Eventually, it all starts to work again, and it's generally pretty reliable, but this is enough of a nuisance that I have to qualify my recommendation. The Pharos receivers (the one that used to come with Microsoft Streets & Trips with GPS Locator) and the DeLorme Blue Logger both seem more dependable with the software to me.
In comparing Garmin GPS receivers, it is important to distinguish the ones that have only a USB interface from those that have serial (or both serial and USB) or Bluetooth interface. Check the specification page for the GPS receiver before buying to determing which type of interface(s) it has. For maximum flexibility in working with Tru-Traffic TS/PP, choose a GPS receiver with serial (or both serial and USB) or Bluetooth interface, not one with a USB-only interface. Be aware that with many of the GPS receivers that support both serial and USB, getting the serial cable requires a separate purchase. You should do this (buy the optional serial cable if it's not included) for maximum flexibility in working with Tru-Traffic TS/PP, as downloading pre-recorded trip logs directly to Tru-Traffic TS/PP requires connecting the GPS receiver via its serial cable. The serial cable may be connected to a USB-to-serial adaptor, if necessary, to plug into your computer's USB port, but the connection on the GPS receiver side still must be with the serial cable, not the USB cable, if you want to download pre-recorded trip logs directly to Tru-Traffic TS/PP.
If you get a USB-only Garmin GPS receiver, or you don't have the serial cable, then at present you must use some additional software to either connect the GPS receiver to Tru-Traffic TS/PP or to download the pre-recorded trip logs to a file for importing into Tru-Traffic TS/PP. You may use the software product Franson's GpsGate to emulate a virtual serial port so you can connect the GPS receiver to Tru-Traffic TS/PP. See the discussion of that software above for more details. One user reports successfully using DeLorme Serial Emulator for this purpose. Either of these options allow you to connect the GPS receiver to Tru-Traffic TS/PP through the virtual serial port so Tru-Traffic TS/PP can record trip logs, but they won't allow you to download pre-recorded trip logs directly into Tru-Traffic TS/PP. To download pre-recorded trip logs, you may use
to download trips and save them in, say, a .GPX file for subsequent importing into Tru-Traffic TS/PP. A FAQ gives some additional details.Starting with version 6.0, Tru-Traffic TS/PP includes additional support for Garmin GPS receivers. You can use the Garmin proprietary interface, instead of the NMEA interface. An advantage here is that in the Garmin proprietary mode, the GPS receiver gives an update every second, as opposed to every 2 seconds. Also, you can download pre-recorded trip logs from the Garmin GPS receiver. This allows you to take just the GPS receiver out in the field, without the laptop, record you trips, then download them into Tru-Traffic TS/PP after you return to the office.
One user has reported great results with the Globalsat BU-353 Cable GPS receiver. While I don't have any personal experience with this receiver, it has some appealing features. It includes a magnetic mount, a waterproof casing, and a 5-ft USB cable so you can easily mount it on the roof of a vehicle with good exposure to the sky. It uses the SiRF Star III GPS chipset and an active patch antenna for high accuracy and sensitivity.
These seem to work nicely. One I've used, theI've personally used only the Magellan GPS 315 receiver, an older model. This worked fairly well, but not quite well enough that I can recommend it without reservation. I found that it fairly frequently stopped reporting a current, tracked, position for long intervals — 10 seconds or more. While recording trip logs, Tru-Traffic TS/PP doesn't like these long gaps. I tested this with a Garmin eTrex Legend, each connected to a (different) laptop simultaneously running Tru-Traffic TS/PP and both sitting side by side on my dash board. I had many more problematic gaps with the Magellan than I did with the Garmin. I'm not sure if the Magellan GPS receiver just lost the satellite signals more easily than the Garmin, or if both lost satellites but the Garmin recovered more quickly, or if the Garmin was just dead reckoning — extrapolating from the last reliable reading — as Garmins do. Probably the latter. But either way, I had many more troublesome gaps with the Magellan.
I don't know if these problems persist with more current models, but the experience of some Tru-Traffic TS/PP users in North Carolina does not sound promising. They're using Magellan Meridians (newer than the receiver I used, but older than the ones available now, 4/24/03), and have reported similar problems. We haven't confirmed that the problems are identical to the ones I had, but everything we could compare sounded perfectly consistent. Right now, I'd recommend using a Magellan only if you have one already. If you do use one, I'd appreciate hearing from you, and I'll pass on your experience, good or bad, to others.
Microsoft Streets & Trips 2009 with GPS Locator
I have personally tried the new "GPS Locator" — the GPS receiver that comes with Microsoft Streets & Trips 2009, and I've tried the one that came with earlier editions. They both work very well, but I prefer the accuracy of the older one (the one manufactured by Pharos) over the newer one (manufactured by Navation). The earlier ones were the Pharos iGPS receivers; although, they sometimes carried Microsoft's logo. See the discussion below of the Pharos GPS receivers for more details. The especially nice thing about the Pharos receivers is that they use the SiRFstarIII chip set, described above, which continues to work well in weak-signal environments, urban canyons, and under tree canopies. More than one user has given feedback about these GPS receivers, and it's all been very positive. Starting with Microsoft Streets & Trips 2009, the Pharos GPS receiver is replaced with the u-Blox 5 technology Navation GPS 168. Initial tests suggest that this works very well with Tru-Traffic TS/PP. For this one, you probably want to set the speed to 9600 instead of the default 4800. After that, everything seems to work fine with this GPS receiver and Tru-Traffic TS/PP. The entire package, including nice mapping software and the GPS receiver, is available for about US$80 on the street.
You can view a performance comparison between the Pharos and the Navation GPS receivers here.
I've tried the Pharos iGPS-360 Receiver in the USB configuration. This seems to work very well. After installing a USB driver, the software sees the GPS receiver's information arriving on the serial port (COM5 in my case) despite its being physically connected to the USB port. Also, I like the fact that the GPS receiver takes the WAAS signals (for improved accuracy), gets its power from the USB port (so as long as my laptop is plugged into the cigarette lighter, both the computer and the GPS receiver have power), it reports GPS position and speed messages once a second instead of the usual once every two seconds, includes a suction cup on the cable for attaching to the inside of the windshield, and comes (or at least used to come) with nice mapping software. The main disadvantage, in my opinion, is that this can't run as a standalone unit – it must be plugged into the laptop (or some other device) to be useful.
Their newer iGPS-500, the GPS receiver sold in Microsoft's Streets and Trips with GPS Locator 2005, 2006, 2007 & 2008 packages, uses the SiRFstarIII chip set for extra sensitivity under overpasses, in urban canyons, and in other weak-signal areas. Unfortunately, it no longer comes with Microsoft Streets & Trips 2009, so to get it, you have to purchase directly from the manufacturer or from another vendor. When using this GPS receiver, by default it suggests that you should set the COM port to 9600 baud, but several users have reported that in fact they had to set it to 4800 baud to get Tru-Traffic TS/PP working with it. Even with this setting, the GPS receiver reports a reading every second. Tru-Traffic TS/PP users with this GPS receiver seem to be very pleased; although, one reports that the receiver introduces an artificial lag, suggesting that you arrived at an intersection a few seconds after you actually arrived. It seems that due to the longer processing time for this chip set, the receiver ends up reporting to the software the current time along with the position as of about 1.5 seconds prior. This user has been able to work around this problem by compensating for the lag during the synchronization step between the GPS satellite clock and the signal controller clock -- the user watches the key signal transition occur, then waits about 1.5 seconds before pressing the Synchronize Now button. The only other complaints I've heard about this GPS receiver are that
I haven't had any personal experience with the Trimble GPS receivers, but Tru-Traffic TS/PP users in two different states have experimented with a high-end one. Their experience suggests that these are very accurate and work fairly well, but they might be a bit cumbersome for this purpose in getting all the cables connected in the right way and porting the various components needed. Also, they report that compared to a Magellan Meridian, their Trimble seems to be a bit picky — quick to lose a fix when the satellite signal becomes weak, and slow to recover a fix when the signal is restored. Their impression is that the Trimble insists on a high degree of accuracy, and when it can’t deliver that accuracy, it’s silent. One set of users' tests suggest that the Magellan works fine in all the Trimble's dead spots around the city. They prefer the Magellan over the Trimble.
A user in Colorado has had success in using the Trimble GeoXT, but for reasons we don't entirely understand, he had to set
Using the NMEA/4800 mode seemed to be unreliable.
Other
There are GPS receivers from other manufacturers, but I have no personal experience with them, and I don't know of any Tru-Traffic TS/PP users working with them, so right now I can't pass on any more information about them.