Limitations
While it is tempting to assume that location based software, such as Nearby Explorer, solves all the
navigation and orientation barriers faced by blind travelers, there are a number of conditions that must
be considered. To better appreciate these benefits and limitations, it is useful to obtain a basic
understanding of how the technology works.
There are several components in play.
GPS
First, the device uses a global positioning system (GPS) receiver to read signals sent from an array of
satellites designed for this purpose. The receiver uses these signals to pinpoint a position on earth and
assign lateral and longitudinal coordinates to that position. In general, a good consumer-grade receiver
can render accuracy to within a few yards of a person's actual position under optimal conditions. More
realistically, one can expect to get accuracy, most of the time, good enough to determine the side of the
street on which he travels.
Some of the conditions that adversely affect accuracy reading satellite signals include the following:
1. Low cloud cover
2. Unusual atmospheric conditions
3. Large buildings that prevent a clear view of the sky
4. Inside buildings or underground where there is no clear view of the sky
Maps
The latitude and longitude coordinates do not mean much to most users, so they must be combined with
maps that contain more familiar landmarks such as streets and places. Nearby Explorer comes with maps
that cover the United States and Canada.
There are several factors about the map data that are useful to understand to make the most effective use
of the software.
The map data all resides on your device, so it is not necessary to have a Wi-Fi or cell data connection to
use the software. If you do have a network connection, Nearby Explorer uses it to request information
about places with the Google Places service. This information tends to be much more dynamic than that
on the maps on the device. Plus, you can label places and benefit from others' labels.
The map data may be inaccurate. There are millions of points of interest and other locations in the data.
It is possible there are errors introduced during the collection process.
Points of interest are marked at a point in the road where the road passes the point, not at the front door
of the establishment.
Street addresses are approximate. They are calculated using a relative distance from the beginning to the
end of the block. You may notice, therefore, that an address is consistently off by a house number or
two. This is normal and cannot be corrected. While the house number may not always be exact, it stays
constant, so once you find that Explorer reports an address at a certain point in the block, it consistently
reports that same address at the same point.
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