Hi, I generally agree with the points outlined in David's post. I would note the following, however:
My experience with a good GPS receiver and the Sendero product is quite different. I have always, under everything except severe thunderstorms--which I can't comment on since I don't travel in severe storms, electing safe shelter instead--have received navigation accurate to about 20 meters (60 feet) at worst, and at least 95% of the time to better than 10 meters. Second, database info is much more comprehensive and getting various updates is certainly easier. I don't get as precise route info and the process of getting feedback on current location is not as easy for me using Navigon. I also find that I need another couple apps like Ariadne to try to duplicate the navigation convenience available with the Sendero product. I'm looking forward to what might be available with their Seeing Eye app. I do certainly understgand that from a budgetary standpoint, this is a luxury. Just my 2 cents. ----- Original Message ----- From: Raul A. Gallegos To: [email protected] Sent: Thursday, August 09, 2012 12:33 PM Subject: Re: Talking gps? David, thanks for the concise explanation of how GPS works. Too often I see people, sighted or blind, who don't understand how it works and base opinions on usability or lack there of and blame it on a specific app when it may not be the app's fault to begin with. People need to understand that there are multiple things involved, user interface, map data, map data source, and points of interest just to name a few. -- Raul A. Gallegos The human race has one really effective weapon, and that is laughter. - Mark Twain Home Page: http://raulgallegos.com Twitter: https://twitter.com/rau47 Facebook: http://facebook.com/rau47 On 8/9/2012 12:39 AM, David Chittenden wrote: > Navigon and TomTom both do and are both accessible. That said: > > People continue having a very bad misconception about GPS. First, GPS uses > a database. The database has coordinates for streets and intersections, > but unless mild turns and swerves are properly plotted with coordinates in > the database, the app will draw a straight line. Maps are always being > updated, and commercial apps do not charge, or charge very little for > these updates. And, if you pay the slight charge, your database will be > updated every quarter. If not, your database will be updated annually. > Contrast this with the blindness specific GPS products where you get an > annual update for a cost which is higher than the total purchase price of > any of these apps, and that is an annual expense. > > Also, in most cases, the actual GPS coordinates for each address are not > in the database. Instead, the database has the starting address, the > ending address, and the number of addresses in the block. Therefore, the > announcement activates when you are a percentage distance down the block > that represents where your address would be if all addresses are equal > distance from each other. In other words, if there are 10 addresses on the > block and you are going to the fifth address, the system will alert when > you are half way down the block. However, if any address takes up more > than 10% of the distance, you will not find the correct address just by > using the GPS system - and this is the same whether you are using a > blindness specific system or a normal system. > > Then, there is the accuracy factor. At its best, GPS can be accurate to 5 > metres (15 feet). Therefore, given that the front of an address can easily > be shorter than this distance, all GPS systems will only get you close to > your desired destination. You need good orientation and mobility skills to > find the actual location. And, if accuracy is more toward average, the > area is within 10 metres (30 feet). Oh, and this means you are anywhere > within that circle, not at the centre of it. > > GPS accuracy is effected by any obsticles that may block the signal (such > as buildings, trees, or even clouds and other weather conditions. On an > extremely overcast day last year, my GPS was unable to give me accuracy > any better than 500 metres (about 1600 feet). It kept placing me in > different towns, and I was standing still watching the display change. It > was quite fascinating. -- You received this message because you are subscribed to the "VIPhone" Google Group. To search the VIPhone public archive, visit http://www.mail-archive.com/[email protected]/. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/viphone?hl=en.
