Choosing a GPS Receiver
From: Newbie (susanandbrent_at_earthlink.net)
Date: 09/15/04
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Date: Wed, 15 Sep 2004 19:32:10 GMT
I am considering purchasing my first GPS receiver. Because I live in a
mountainous region, being able to know my elevation is of primary importance
to me. Instead of spending about $100 on a digital altimeter, I would like
to buy a GPS receiver for around $300. I have spent several hours on the
gpsinformation.net site trying to figure out what receiver I need and what
elevation accuracy I can expect, and I am still confused, partly because I
am not sure which information is obsolete and which is still accurate.
According to an article written in Feb. 01, an elevation error of up to 75
feet can be expected with GPS, but DGPS dramatically improves accuracy where
available. I found Coast Guard information which seems to indicate that my
location in Jackson Co, NC is not currently in a DGPS-covered area, but that
a new receiver is planned for Dandridge, TN (about 70 miles away). The site
says that construction of the Dandridge site will start in 2004 if funding
is available, so I am hoping it will be built soon. But I am unsure whether
I will be within its range--although other sites seem to have a range of
about 150 miles, I wonder if being on the other side of the peaks of the
Appalachians will keep me out of range.
I assume that someone interested in accurate elevation readings would want a
receiver with a barometric altimeter. I read about models in which the GPS
altitude can be used to calibrate the barometric altitude, but again the
question of accuracy of the GPS altitude arises.
I am also concerned about getting a receiver that will operate as accurately
as possible in moderate tree cover in a mountainous region. I would usually
have access to open sky when beginning a hike, and/or at intermittent times
later, but given my geographical location, I probably won't have access to
the SE horizon because of the mountains. I have read that WAAS probably won
't work in tree cover and/or mountainous terrain, so my assumption is that I
can't count on that accuracy until more satellites go up. Do I need a unit
that has a quad helix antenna and/or accepts an external antenna? I am
impressed by the reviews of the new eTrex Vista Color, but it doesn't have
either of these features. One review said all the eTrex models have more
reception problems than other Garmin receivers, but another part of the
review said "Antenna is slightly smaller than on larger Garmin units, but
gives sensitivity almost equal to the larger Garmin receivers."
In general, my situation is as follows:
I live in the mountains of western North Carolina. I am interested in
hiking and driving around the region while keeping track of my position and
elevation as I explore new areas. I may be shopping for a new house soon,
and some of the houses will be on private or homeowners' association roads
that may not be on software maps. I want to know the precise location,
especially elevation, or each house I visit. (My experience is that both
sellers and agents tend to be vague and imprecise about the elevation). I
hike, but I am not a "serious" hiker--the longest hikes I take are several
hours to half a day-but I take short hikes frequently. These hikes are
usually in moderate-to-heavy tree cover. I also like to keep track of my
elevation on car trips in the eastern US. I would want to be able to use
topo maps for my region, but I am concerned about the prospect of having to
pay $100 for proprietary software for the entire US, especially since I
would never use 95% of the maps. I feel comfortable working with some of
the more technical aspects of mapping, but I don't think I would use
sophisticated features very often. I could live with either serial or USB
connection to my PC, although of course USB would be more convenient. I
have absolutely no interest in marine or aviation features. Of course, like
everyone else, I don't want to pay more than I have to, and I would like to
find a vendor that both has a good reputation and offers a reasonable
discount.
In summary, my questions are:
1. What is my status regarding WAAS and DGPS, and how does this influence
the type of antenna I need?
2. Given the answer to #1, what receiver is best for me?
3. What is the best way to find a reputable discount vendor?
Thank you for any help you can give,
susanandbrent@earthlink.net
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