Am I doing something wrong?

The satellite configuration in northern California from mid December 2000 to the end of February, 2001 is so poor that I might as well leave the Locus at home and forget GPS.

I can't log more than 5 or 6 sats under the best conditions all day after about 11 AM., and my mission planning indicates that this will continue for two months.

It takes over an hour to get any static shots. Is this a normal sattellite arrangement?

It seems to me that if we have 24 (or is it 32) sats, its an awfully bad roll of the random dice or whatever that we only have 5 satellites visible to the receivers, all day long.

Am I missing something?

Using almanac downloaded today with 28 healthy SVs available and a elevation mask of 10 degrees, location San Francisco Bay Area, you would have between 8 and 10 SVs throughout the morning hours, dropping down to 6 and 7 SVs in the afternoon. Only time you get down to 5 SVs is for two brief periods between 4:00am and 6:00am.

Should still be able to get some work done.

Yes, the constellation is fairly weak during the times you indicated. 6 satellites are the most that will be visible at a 10 degree elevation mask. This scenario does happen occasionally because the constellation is always changing its position with time. There are 28 satellites as of today's date.

Can you give me some more details on your survey area -- are your survey points free of obstructions? This becomes even more critical when the constellation is weak.

Do you have any structures nearby that could cause multipath?

Also, how long are your baselines? How many flashes are you getting on your LOCUS occupation timer?

Regards,

Richard Phelan
Magellan Technical Support
1-800-229-2400

Your estimates of satellite availability are appreciated, as a check.

I have found with the locus recievers that they work very well as long as you have 7 or 8 sats being logged, but that during periods like this, when there are 5 or 6 sats being logged from a clear site, you can forget about kinematic, and expect to spend 20 to 80 minutes over static sites.

Tree cover, the mysterious signal to noise ratio, is a matter of learned trial & error. I always occupy a point several minutes beyond the first "beep" depending on the number of (leafless) branches overhead. With this approach I have had good success.

The thing is... why is it that with 28 satellites, there are only 5 available for several hours? You will not do any kinematic work with 5 sats.

Have these satellites been put into orbits that provide extremes in coverage? for a reason?

I mean, if I was going to determine the orbits of these things, I would strive for full and even coverage, maybe even stick a few stationary sats.

It makes me wonder.

By the way, I am talking about observations within 1500 feet of the base receiver.

Seism,

In my limited experience, I've found the "recommended occupation time" versus "measured base line" to be directly opposite the recommendation from the manual and software. Seems the longer occupation on the shorter lines provides much better solutions and repeat vectors. To be certain, if used for control or boundary, I run all points at least to the "solid" 20k signal.