[nagdu] Basics of GPS

[Jenine Stanley]

Here's just a little about GPs devices. GDf plans to have some material
about choosing a GPS device and working with it and your guide on our web
site later this spring, but this is a taste of what will be there. 

What is GPS technology? 

GPS, Global Positioning System technology is a way to pinpoint your position
using triangulation between at least 3 satellites and a receiver. 

How accurate is GPS technology? 

Civilian GPS technology is accurate to around 10 to 15 feet. When using a
GPS device, imagine yourself standing in the middle of a 15 foot circle.
Accuracy can be effected by weather, stormy or excess electrical activity in
the weather for example, tall buildings or large reflective surfaces like
bodies of water, and the strength of the receiver versus other interference
such as high capacity power lines. 

Does GPS work indoors? 

No. You must be able to see the sky in order for your GPS receiver to work.
Some buildings with large windows, skylights  or atriums may allow you to
get a GPS signal but it will be less reliable due to the potential
reflection off the glass or other materials. GPS may also not work in some
vehicles with protective coating on the windows such as trains or some cars
with UV window treatments. 

What makes GPS products for blind people so special? 

One feature really stands out in the GPS products specifically designed for
use by blind people. Intersection description is a method, using algorithms,
that describes the layout of intersections as you approach them on foot.
This description is not generally found in standard GPS products that simply
give the street name. Knowing how an intersection is laid out or when you
are passing a cross street on the other side of the street from you that
doesn't go all the way through can be extremely helpful in navigating your
way around. 

You can use the intersection description feature when walking or simply have
the device announce the street name as you approach it. This is handy when
in a vehicle such as a taxi or bus. Most blindness GPS products can be set
to which ever announcement type you like then left to work without you doing
anything else. The devices can also be set to announce what's around you
such as stores, restaurants, public buildings, bus stops, etc. while you
walk. They also have a host of other features. 

What are the major GPS products out there now for blind people? 

There are two major stand-alone devices for GPS navigation and several
options for using additional devices with a GPS receiver. 

The Trekker Breeze is a stand-alone device made by Humanware. It is about
the size of a large TV remote and has 9 buttons on its front. It was
originally designed for people who did not want a complex device for GPS
navigation. 

Humanware produced the original Trekker device using a mainstream PDA which
is no longer available. That device had around 36 buttons on it and had the
ability to browse routes when not in the specific area. The Breeze does not
have this ability but does allow users to put in addresses for later
navigation. 

Unfortunately, the maps used by the Trekker Breeze are only updated
approximately every 12 to 18 months by Humanware. If your area doesn't
change much, this is not a large factor but if you travel or live in a
dynamic area, points of interest along your way may be reported incorrectly.


The Kapten Plus is produced by Kapsys in France. I do not know who the
current US dealer is. Leader Dogs used to sell the device and provide
training but I'm not certain they do this any longer. 

The Kapten Plus is about the size of a credit card and about as thick as a
small package of gum. It has 9 buttons on the front as well but they are
significantly smaller than those on the Trekker Breeze. The Kapten Plus is
controlled through a combination of voice input using a headset and
microphone, and the 9 buttons. It also has an MP3 player and FM radio. Both
of these will work while using the GPS functions. 

The Kapten Plus does not announce cross streets when in vehicles that are
moving at more than 10 mph. It also will not announce points of interest as
you pass them but will tell you about them if you ask it. 

I have used both stand-alone devices in Manhattan, on the streets and the
buses and they both worked fairly well at keeping track of my position. If I
was walking near a tall building or one with a highly reflective front, they
might report me one street off but generally they were accurate. 

Sendero Group produces GPS software for a variety of platforms. This
software requires a device such as a braille note taker, the Braille Note or
Braille Sense, or a smart phone such as the HTC Ozone. The Sendero software
is the engine for the Mobile Geo GPS program for smart phones on both the
windows and simian platforms. This software does not require a data plan for
your phone, but does take up considerable space so it is preferable to
install it on an SD card rather than the phone itself. 

To use the Sendero software, you will also need a GPS receiver. This is a
small device that is paired via bluetooth connection with your notetaker or
phone. 

The Sendero maps are updated regularly, at least once per year. 


In order to use the program on your notetaker, you will need to install it
and be able to give it commands, so the notetaker will be exposed to some
weather conditions at times. 

What about apps for the I-Phone and Android? 

I can't speak to any apps for the Android phones but would welcome any
information about them. 

there are a number of apps for the I-Phone that provide differing levels of
GPS information but currently none provide the same level as the Trekker
Breeze, Kapten Plus or Sendero products on notetakers or phones. The apps do
not provide intersection description, nor do they announce upcoming street
names. If anyone finds an app that does announce upcoming street names,
please let me know. 

That doesn't mean phone apps aren't useful. I personally like Ariadne GPS,
an app for the I-phone that gives address and street name, announces street
changes as you travel in a vehicle and can show you what's around and plan
routes. 

Some other phone apps that people like include: 

Navigan, which has been updated recently to restore some of its
accessibility.
Sendero Look Around, an app that, when you shake your phone at an
intersection, will give you that intersection's description and what's
around you. It does not follow you though if you move on and you must shake
the phone at each intersection to receive more details. 

Where to is an app that can give you directions to nearby points of
interest. 

My Way and My Way Lite are both produced by the Swiss Association for the
Blind and are based on the Lodestone navigation system. In this system users
set their own markers as they go and streets and points of interest are not
announced. I've just begun to work with this app so don't know too much
about it yet but it has promise. 

Kapten NAm is the Kapten North American version. This app is a commercial
product with a $7 per month fee to use the data/maps and does not have any
of the blindness features the stand-alone Kapten device has. 

GPS Drive is similar to Navigan in how it works and is primarily designed
for use in vehicles but it can give you walking directions to points of
interest or addresses as well. 

Maps is a native I-Phone app that can give directions to nearby points of
interest as well as serving as the base for several of the other GPS apps
mentioned above. These maps are updated regularly in real time. Prices on
the apps listed above vary from $1.99 to $60.00. 

Why does it seem like the GPS devices used by sighted people are more
accurate than the ones for blind people? 

The devices used by sighted people, such as Tom-Tom, On-Star, Garman and
others have one additional feature that enhances the GPS, human vision. A
person can see the GPS display telling him that the place he wants to find
is approaching on the left. Remember that 15 foot circle we stand in when
using GPS information? Human vision has a much greater circle to span. The
address might be 50 feet away and Voila! The sighted person sees it and goes
to it while the blind person must still rely on the GPS instructions to get
closer. 

Both systems use the same satellites and same receiver technology to gain
the information. Honest. <grin> 

What other skills do I need to work with GPs technology? 

GPS technology alone does not replace the use of a cane or guide dog. It
also requires that you have some understanding of street layouts and be able
to keep track of what side of the street you are on and the address system. 

GPS technology assumes you are a car and places you in the middle of the
street to navigate. On some larger roads, there may be two or more GPS
positions for that road. GPS doesn't know if you are walking on the left or
right side of the street. 

The Kapten Plus device does state that it has this feature but I've only
found it accurate about 50% of the time. 

When we taught GPS tecnology at GDF, we had a saying for people when it
comes to trust: ""Gut, Dog, Trekker." 

This means that first you should trust your instincts and O&M skills. Next
trust your cane or dog. Finally, use the information from your GPS device
and plug that in to what you already know about your environment. 

That's just a brief look at GPS. As I said, we hope to have much more info
later this spring.

Currently I have a Trekker Breeze and a Kapten Plus, at least 7 apps on my
I-Phone and have used Mobile Geo in the past but on a very slow phone so it
really wasn't a good test. Personally, I prefer the Trekker Breeze, though
its maps are outdated. It's easy to use, gives me all of the info I want,
intersection description when walking, cross street identification in
vehicles and a nice clear voice. I'm still hoping for that I-phone app that
will equal the original Humanware Trekker software. That imho was probably
the best and easiest to use product I've worked with. 
Jenine Stanley FSO-PA
U. S. Coast Guard Auxiliary Flotilla 18-06
Columbus, OH 
cga.jenine at wowway.com

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