One thing that the discussion of the advantages of even L1 GPS in urban surveying brought to mind was the configuration that Peter Lazio described for some GPS surveys he'd made in New York City. As I recall, Peter had his base receiver actually inside the cab of his truck with only the antenna exposed. I seem to recall it as having been attached to the truck roof via a mag mount, but that detail may only be what I would think about doing.
For L1 surveying with three receivers, the idea is that the base antenna is simply in a position that won't be reoccupied. All of the vectors to the two roving receivers are solved and from them the relative positions of the rovers are obtained. The relative position of the antenna on the truck roof will of course be obtained as well, but it won't be a monumented point and so is ephemeral.
While the exposed antenna is a bit of a risk, it isn't nearly as much as having receiver, tripod, etc. left unattended.
Being frugal (okay, cheap) in nature, most of my equipment is pretty old. Still, I tend toward the paranoid when it comes to equipment security. I have a hard time driving away from a receiver -- even in a rural setting -- though I do it when necessary. I can't quite bring myself to do so in the city.
I'm just as bad when it comes to my ancient robotic total station: I employ stainless steel cables and a padlock to discourage theft. Most self-respecting thieves wouldn't look twice at the old rig, but locking it down gives me enough of a sense of comfort that I can leave it unattended, even in an urban setting.
> Being frugal (okay, cheap) in nature, most of my equipment is pretty old. Still, I tend toward the paranoid when it comes to equipment security. I have a hard time driving away from a receiver -- even in a rural setting -- though I do it when necessary. I can't quite bring myself to do so in the city.
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As I recall, Peter had his base parked on the upper deck of a parking garage on one job, which I thought was an interesting way to get both a fairly unobstructed sky view and better security than on a public street.
In rural areas, I always leave the base receiver behind a fence or a gate, far enough from the road that (a) it would be easy for passing motorists not to notice or (b) it would take more of a hike than the opportunistic thief would probably be up for. The tops of road cuts can be good also, not too far off the road, but out of sight of passing motorists.
> One thing that the discussion of the advantages of even L1 GPS in urban surveying brought to mind was the configuration that Peter Lazio described for some GPS surveys he'd made in New York City. As I recall, Peter had his base receiver actually inside the cab of his truck with only the antenna exposed. I seem to recall it as having been attached to the truck roof via a mag mount, but that detail may only be what I would think about doing.
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Here are photos: http://www.plazio.net/Images/Queens%20Images.html
This was the first time I left the GPS unattended like this and I was a bit nervous. One thing in your favor is that people in the City are used to seeing odd things all the time. As long as the setup is not something that looks familiar, like a tripod, or useful they will generally leave it alone. Also the yellow color of the truck suggests an official capacity which may be a deterrent for some.
The truck antenna was positioned using OPUS. Radial stations were then positioned using fast static from the truck antenna. Once the radial stations were determined the position of the antenna did not mater any more. It had served its purpose and its position was disposable.
Peter Lazio
Has anyone used something like this?
near larger cities Leica and Trimble dealers have set up private networks that you can tie into live. e.g. Kara CORS site
What ever happened to the time honored concept of hiring someone to watch the receiver? I myself know of at least a dozen people who have lost their jobs who would gladly read a book while watching a receiver for a fifty bucks.
Or I could rent you my fully bonded attack poodle that is full certified for urban duty.
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I almost hate to ask, Philip, but was the control point being positioned just a corner of the inlet grate frame, as appears? Why did the poodle choose that particular point instead of, say, a fire hydrant?
The miniature poodle that set that pk nail at the corner of the grate actually worked for an out-of-State consulting firm that set up the town of Old Orchard Beach GIS. I was shocked at the location on the control points. Of the 10 control points I recovered, that one was the best one. I had no choice in the matter.
The photo only caught the poodle at that moment in time. She was actually shaking her head in disbelief that the consultant actually used that point for control.
From the paint then I guessed that this was one of their photo control points for a aerial project.
Actually very bad to use paint on a storm water inlet. Not kosher for clean water.
GPS in the City: Who's Watching the Base? _ Deral
That's an old fly point. Look at the rust coming through on the inlet.
I try to put the base in a secure location. One time we found a fire station on a project near Santa Barbara (when I worked for State Parks) and they were kind enough to let us set a rebar/cap for our project base. The fire station wasn't in a terribly public location (a ways up a private road) and we had sort of built in security.
The other way is to put the base somewhere secure on the client's property.
If no where secure can be found then I have hired a college student to watch the base. They like making a little money and they can do whatever they want as long as the base stays there. I gave the job to daughter one time then I gave the job of watching daughter to her boyfriend :). They sat in lawn chairs doing whatever all day. The only thing they didn't have was internet.
In the middle of the State Forest it's not really a problem. Usually we are working at least a couple of miles from the paved highway and behind a locked gate. It's open to hikers or mountain bikers but they don't really want to haul a bunch of heavy gear out with them. It's a rare thing to see a member of the public.
'they didn't have internet'
Good lord O'Roly. Are you that cruel a master? How ever did they survive without the internet and not being able to send each other e-mails and such.
Oh the Horror of it all.
You are just too cruel. 🙂
deral
given descending income I suggested we could give up the internet and cable TV to "the Boss" yesterday.
You would think I suggested we live in tents and use stone tools 🙂
deral
Good lord. I bet that got the group looking for cost cutting measures elsewhere.
"Okay, I think we can get by on beans for meals and take out the light bulbs. We can use the toilet down the street at the quicky mart".
"BUT PLEASE DON'T KILL THE INTERNET"
deral
well we dropped the Blockbuster internet movie service, that saved 10 bucks a month, YIPEE!
Well geez Dave, next time pick a point near a business that has WIFI.:-)
there might be free WiFi in the 5 story medical office building nearby but I didn't want to get close enough to pick it up, I'm just a meany 🙁
deral
You have moderate weather? Yes? Just have the family fan out and find a bunch of unprotected wifi connects around the hood.
People may wonder in a week or so why your family is always sitting in lawn chairs out in the front yards though. Just have them all wear survey vests and you can pull it off though.
Subscribe to a VRS net. They'll watch the base for you as you travel anywhere in the state. However, you'll need a dual-frequency receiver ... but only one. That's a whole lot of years of subscriptions instead of the cost of a base station.