I have something to say about our
mainstay — GPS — and its troubles of late. So many people in the
survey/mapping community have asked me when this problem is going to be resolved.
The problem is there aren’t enough healthy satellites for surveying community
I think the GPS decision makers don’t believe there is a problem because
with a clear sky, you still get a 3D position, anytime, anywhere in the world.
Herein lies the problem: we don’t usually work in clear-sky environments.
Neither do consumer GPS users. My Honda Odyssey GPS navigation system doesn’t
get a GPS position fix nearly as much as it used to.
(Just to clarify: I’ve spent the past 16 years in the GPS survey/mapping
industry using many brands of GPS equipment and software. My first ten years
in GPS were spent as a product manager and the last six years as a GPS user
and consultant. I’m a non-partisan advocate for the GPS user community.)
The fact is that GPS has suffered more outages to key satellites (or satellites
in key orbital slots) in the past year than it has since GPS was declared operational
in the early 90’s.
PRN 25 has behaved like a legacy Jaguar automobile for the past 6+ months:
an hour shut down for maintenance for every hour it has spent operational.
Of course I’m exaggerating, kind of, but I’m sure you understand
my point if you’ve been using RTK with any frequency for the past 6+
months. I reported last month that the next GPS satellite launch (scheduled
for September ’06) would most likely replace PRN 25 according to the
Chief GPS Liaison at the USCG, Doug Louden. But I’m beginning to doubt
this, given the precarious slot that PRN 30 occupies and its surprisingly rapid
decline in health. PRN 30 is on its last clock from what I understand. It isn’t
as old (9.5 yrs) as PRN 25 (14 yrs), but it’s still two years past its
Other GPS satellites are significantly past their design life and heading
for failure. You can’t use RTK a full day with the current GPS constellation
even with every satellite healthy. Take one out that’s in a key slot
like PRN 25 or PRN 30 and it gets really ugly.
I think it’s not unreasonable to ask the GPS JPO for a healthy, reliable
constellation of GPS satellites.
Delays in launching replacement satellites have been so significant that GPS
users have quit asking me about new launches. It looks like only one will be
launched in 2006 and only one will be launched in 2007 — if the schedule
doesn’t slip further. This is a far cry from the “three-a-year” launch
plan laid out a few years ago.
I don’t believe the GPS JPO thinks there is a problem, but you only
have to look at the new product introductions to understand that there is. For
years, most survey-grade GPS manufacturers ignored GLONASS and thought it would
go away, and GPS would fill the bill. However, in the last 12 months, the number
of survey-grade GPS manufacturers offering GPS/GLONASS products has at least
Meanwhile, GLONASS is pushing forward with an aggressive launch schedule.
Three in December ‘06, three in Q3 ’07 and three in Q4 ’07.
Furthermore, the two new GLONASS satellites that are already in orbit are reportedly
to be declared operational in the next 60 days. Granted, only time will tell
if they can honor that schedule, but even launching half of what they plan
would be significant.
So, I’d like to raise my hand from the back of the classroom and say
the Survey, Construction and GIS industry segments aren’t happy with
the way GPS is performing these days.
— Eric Gakstatter