I've been through the whole depressing drama of looking at new GPS gear for the past 6 months.

RTK is too expensive and we could never have the workload to justify it, and so the Locus looks better everytime we see it!

What do you experts say? How many Locus units should I get?

Most of our work for GPS would be placing control stations down freeways or highways for watermain and sewer construction, and the occasional RTK pickup.

MY humble opinion is for 3 units (and a one-man operation) as follows:

1/ 2 on base stations and one doing repeat obs ("am, pm" rule) with RTK, which would be very quick!

OR

2/ 1 on a base station, and 2 leap-frogging in static mode.

Experts?

they have a get one free promo right now. If I were you, I would buy three, get four, put two on your known controls, then you can move the other two around as you wish, and still have two baselines coming in to each. Plus, you won't have to make sure the two unknowns have common times between them because both bases will be constantly going.

And, if you do use all four in one network, you get the cross ties for free.

I'm admittedly biased on this issue (you should buy at least 10). :-)
Seriously, when I started surveying with GPS we began with 3 receivers. We quickly realized 4 made for a much more efficient operation. I've used as many as 8 on a project, but beyond 6 or so, logistics become much more complex. 4 is a good number. If a big project comes your way, you can always rent more.

Get three, and rent more when you need them. I like that idea.

This is the place!

I started with a pair, then went to three. Two will run you to death. Since you get N-1 (N being the number of receivers) independent vectors, you can see that three is twice as fast as two. More than that and it gets fun. We once used five, left one as base and I moved two while an associate moved the other two. The end result was a lot of vectors that did not have enough data to process with good results, due to the lack of comunication between us. Looking back, what I probably could have done was to set up two jobs; one with my data and one with his. Then after processing each, importing the processed vectors from one job into the other, and Heaven forbid NOT electing to "process all".
I'd say go with three, leave two of them static and move the third one around. Of course if you want to be the one man show, you need to think about where in your vicinity you have a combination of a "wide open space" and a secure location for your static bases. Or you could just go the insurance route.
Disclaimer: I aint no expert!

I vote for three also, thats what we use and it will work out good for you "when" you get into kinematic because you will have a check on all your shots. The deal they have now is too good to pass up.

2 are of course minimum 1 vector at a time 1 job.

3 allow you to do 2 vectors on one job. If the work is there to support them then you have double production for 1.5 cost assuming the cost per receiver is the same which it probably won't be.

4 allow you to do either 3 vectors at a time on 1 job.
- or-
you can split them up and do 1 vector at a time on 2 jobs. Thus provides more flexibility.

However if they are going to sit unusued any significant amount of time you would probably be better off tending to smaller # and you would only have to evaluate your time saved by additional units giving you back billable time in other money making work you would be doing instead of babysitting receivers over multiple sessions.

I have 3. More than once I've wished I had 4 or 5. Then I snap back to reality. Without the extra manpower to guard units scattered all over the country side, and careful time management/coordination, I would suggest starting with 3. Like Dave said, when you do get up and running try to find a few "secure" sites in your work area for project controls. Sure makes the day go smoother if you can reduce the mental anguish of leaving unattended units.

ditto the disclaimer also. I'm an ex at alot of things, but "pert" ain't one of them.

J.D. Billings

x=an unknown quantity
spurt=a drip under pressure