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Tuesday, November 25, 2008

How GPS works.

I was going to continue along the GPS details, but i found one of the best explanations I've seen. It is written by Brain, Marshall, and Tom Harris and it is titled "How GPS Receivers Work" in HowStuffWorks.com. Take a read if you have the time.
http://adventure.howstuffworks.com/gps.htm

Sunday, November 23, 2008

Using your cellphone when abroad

Another important apparatus for the road is the ubiquitous cellphone. Advances in technology have made it easier to carry a phone when you travel overseas. The vast majority of the world has selected the 3GPP standard (GSM) and since 2005 most GSM phones are quad-band, which means they are compatible with most networks around the world. North America is unfortunately the exception.

The market is roughly split in half with Verizon, Alltel, and Sprint (not the Nextel side) in the US; Bell and Telus in Canada, and Iusacell in Mexico being compatible with the 3GPP2 (CDMA) standard. Whereas AT&T, T-Mobile, Rogers, and Telcel are GSM carriers.

Before you jump on the plane it is a good idea to call your service provider and ask for the roaming agreements in the countries you will visit. They will either charge you a flat fee to enable international roaming or it is already in your plan. If you have to pay a fee, you can disable it upon your return. They will also know if your phone is compatible in those countries. If needed, they can provide you one to use during your trip.

If your provider is one of the CDMA carriers above, you will most likely need another phone with a different number that they will provide for the duration of your trip. Although a lot of new high end phones are now worldwide - which means they support both technologies - like the Blackberry Storm.

But buyers beware: International roaming is extremely expensive. It does not use your included minutes and can really add up. If you have a data plan that you use for email or browsing it can be a budget killer. You can disable the data service and re-enable it when you come back.

A cheaper idea is to buy a prepaid phone in the country you will travel. It is typically inexpensive and you can find them relatively easy in a shopping mall. You will of course get a different number, but you will save lots of money. Once you buy your local phone you can email the number to whoever you want. Also note that calling long distance from these prepaid phone can be expensive too.

SMS (aka text messaging) is the most cost effective way to communicate when abroad. You will pay for every message while on your trip, but it is typically $US 0.10 or so, a bit more for international messages. Again, call your carrier to make sure SMS will work during your travels.

Enjoy.

Monday, November 17, 2008

PhotoTrackr Lite with GPS, Geotag your pics

I just found the Photo Trackr (what's with the misspelling of words, Razr, Flickr, Trackr). It seems to be a good idea, but 2 misses:

1. AA batteries that last 22 hours! Who thought of that? Why not a rechargeable LiION with a USB cable?. I can see a brilliant marketing person saying, "let's save the few bucks on a rechargeable and charger so we can sell it for $99." Wrong. People will pay $10, maybe $20 more for a battery that will last 3 years. Big miss.
2. It is unclear how to use it. The picture in the manual shows a PDA connected to the device. Why will a need a PDA? If I have to use my phone, I might as well use the GPS in it. And, oh, by the way, it has a rechargeable battery that lasts more than 22 hours.

One cool thing, though: it has a motion sensor to activate when you move and supposedly save battery.

Keep whishing, my fellow tech-travelers. Maybe soon someone will come up with the right combo.

Saturday, November 15, 2008

Geotracking or Geotagging your pics

If you ventured to this blog and read my first 2 postings, you're wondering what's going on. Well, let me connect the dots for you.

In my ideal camera with GPS we figured that it does not work since you would have to keep your gps on all the time or it will take a very long time to get your location to mark the pic. But if your GPS recevier was connected or even better, part of your cellphone - and it had a software to take advantage of your cellphone's connection - you could get your location in seconds.

Snap your pic, go to your phone's gps software, and voila...in a matter of seconds you have your coordinated so you can write them down in your pic log (you do keep a pic log when you travel, right?).

Now if only someone had a bluetooth or usb connection from the phone to the camera so your pic gets "mapped" instantly, life will be good. Even better if your phone had software that pulled the pic from your camera, add the coordinates, and send it directly to Flickr or post it in Panoramio exactly where and when you took it.

Keep enjoying your travels..

Tuesday, November 11, 2008

What is a "connected PND"

This week I learned TeleNav launched the Shotgun, a connected PND. The advantage of a connected PND is that you can get real time POI updates, traffic, and weather feeds. But more importantly you can get a faster initial fix. This is why:

As you know, gps systems work with a constellation of satellites that send time stamps to a receiver. By calculating the time of arrival of those time stamps and knowing the location of the satellites you can calculate the location of the receiver, aka get a fix (that is a geographical fix, not the other kind). This process is called triangulation.

In the triangulation process I described, besides the timestamps, the recevier needs to know the position of the satellites and then find at least 4 on site. It typically takes several minutes to find 4 satellites, but if you knew where they are, you'll find them faster. Satellites follow orbits that are roughly known. The long term orbital postions of the satellites is stored in a file called the Almanac and short term variations are called ephemeris. Typically PNDs download the ephemeris from the satellites at a whoping speed of 50 bps (that is bits per second) so it is sloooow. This file is valid for several hours and it is typically downloaded when the device is first turned on during a 24 hour period or so. This can take up to several minutes. If you had a faster connection available to download the ephemeris you could get a much faster location of the satellites and a faster first fix. A connected PND such as the Shotgun or the defunct Dash has a cellphone like connection that can be at least 1000 times faster than the satellite. Hence, a connected PND can get the first fix in seconds. Good stuff.

Is that worth a $10 / $12 monthly fee?

If you have a TomTom you can get the ephemeris file from your PC via the connection utility before you leave home. It is valid for a bit more than 24 hours so you get the same effect. If you remember to plug it in every night after you come home, and take it back to your car when before you leave you will get the same effect for free. I never remember so I have learned to get a slow fix.

The traffic and weather feeds do require a monthy fee after the first 6 months. I tried them and found them not that useful. Granted my commute is 20 miles boring and usually traffic free.

It is not clear to me whether you can use the Shotgun overseas as a connected device and I belive it does not include maps outside the US or Canada. So as a traveling companion I'm not sure of its value.

Enjoy Tech and Trips

Sunday, November 9, 2008

Where the heck was that picture taken?

My pet peeve:

How many times have you come home with 25G of pictures and forgot where you took them? Well, you could always take the picture and log the GPS coordinates. It is painful, terribly painful, especially if your PND does not support some kind of "quick fix" technology - most current PNDs don't although that's about to change (more on this on a future post). So why isn't there a good digital camera with an integrated efficient GPS? I know they have been some failed trials, mainly due to battery consuption of the gps itself.

I just saw the new GEO35 from Wolverine. It looks like it is what I'm looking for, but I have to believe it drains the camera battery. Has any one tried it? Why not a belt mounted GPS receiver with its own battery so it maintains location. Snap your pic, plug your your gps and off you go. I know, I know, some of you are thinking, "plug it in?, that's so 1990's. Use bluetooth." Maybe so, but the battery will have to be bigger ...

Photo Trackr seems to work well (I have not tried it, but reviews seem positive). it works by syncronizing time in your camera and the GPS receiver. then some software on your computer does the tagging.

I'd love to hear opinions of users of the GEO35, Photo-trackr or any other camera w/gps.

Enjoy your TechTrips.