GPS again

John Giles, post: 334195, member: 57 wrote: So somebody tell me something that would talk me into buying GPS.

Do other surveyors in your area use GPS effectively? Unless you want to learn the hard way, I'd look around and see what's working for others doing similar work in similar conditions.

Be very, very cautious about statements from sales people. Even the ones that really know what they're doing are heavily vested in making the sale, and much less interested in whether or not you get a good return on your investment.

For what it's worth, I don't use GPS under trees or next to buildings -- I just don't want to take the chance of getting a bum result. I do most of my work with a robotic total station.

Up front! It's not going to work under forest canopy. For setting up baseline outside of forest canopy, it's great! I use gps on ever job I do. I run static post processing gps. In the wide open sky. I see rtk, rtn gps used every day i my area. But never in the forest where I'm working every day. Wish I owned a robot thou!

I held back, purchasing instead static receivers.
Like your comments I'm more often than not in or near trees.
Static (Stratus - 3 of) have and are indispensable.
But then RTK lured me into going that way.
Still don't use it much, but when I do couldn't think of a better way to go.
How "loose" is your definition "generally never going to be....."?
If you don't have Any GPS capabilities how would you, do you, put surveys on Grid Datums now?
I've always found that something like this, once purchased, gets used far more often than first imagined.
It opens up other opportunities not previously considered or able to be.
Can't speak for you, but influencing factors would be your age (wherein your career are you), type of work undertaken, possible future uses if purchased, obvious your income and cost of purchase. Can you hire one easily and quickly?
As to canopy, trees, buildings etc. Maybe old in ideas, but I'd want hands on experience before taking a salesperson pitch.
If it's worth selling it's worth a real life demonstration in the sort of conditions you describe. And not just a quick half hour stint, but coming back in 1 or more hours and rereading same points.

I think you have some great comments already here. First, you have to look at what the other guys in the area are doing. I think that there are a lot of West Virginia Surveyors using GPS, but only as a tool. I think there may be better tools for you if the majority of your work is under canopy. GPS may be something you could add later.

GPS doesn't work under trees. Doesn't matter what they say, what the manufacturers promise, doesn't matter who on this site drinking the Javad Kool-Aid says it will work...it doesn't. It may once in a while, you may get lucky, you may be somewhere you'll have just enough open sky, but on a normal basis you won't.

That being said, Jules is right. It is great for setting up baseline outside of canopy. Sure beats the alternative!

That's another part of it, the number of corners I have to locate on each job that can't be GPS'd. There are generally at least 10 corners per survey not counting tie monuments.

I surveyed 0.47 Acre yesterday. Two corners may have been able to use GPS on. The other 7 and the road shots were all under canopy. And one of them I'm counting as a possible was beside a utility pole the other was about 20' from a larger Hickory. I don't know what that may have done to the accuracy.

I surveyed 48 Acres a week ago. 25 corners and probably 3, may have been able to gps.

Over the last three jobs I've done. I've had to either set or locate about 45 corners not counting road shots. Out of those there were 7 that I believe were in open enough ground I could have possibly GPS'd.

Also how long am I going to have to observe each corner to get good results?

Richard, post: 334210, member: 833 wrote: If you don't have Any GPS capabilities how would you, do you, put surveys on Grid Datums now?

I don't. It's never needed. All I do is boundary work based on a magnetic. That's the way we do it here.

John,
If you want to take a single Rtk or even static observation and be 99% sure its the correct location, then No I wouldnt advise under canopy. I am talking about deep dark woods, probably in a valley to boot. If you think of it as a recon/check tool then Yes it will help and will pay off out in the open in little time just closing control networks.
Sometimes you will get lucky or close enough if you static long enough, but you need multiple shot on multiple days, record measurements, or a traverse to get confidence in my experience. Just don't trust one shot with it as your ONLY check to a point without redundancy. Try a static system you can turn into Rtk later, or 3 cheaper static units?

My 2 cents from more than a few years with it and still learning daily.

I have always said that WV is the TOUGHEST state to do GPS in. Sure, there are plenty of places where it works fine. But for most rural boundary surveys I would say no.

If you have no need for state plane coordinates, or geodetic azimuths, and you do mostly boundary surveys in WV, I would say don't waste your money. I met Mr Sipe about 25 years ago at a WV conference where I was giving a class about GPS. He was interested in what it did, but of course he said it could not replace the compass in retracements.

Get a good robot.

John,

Can't agree with you more. I started surveying in West Virginia in 1974, continued surveying there for about ten years. Too many trees for much GPS. I got into GPS after leaving there and having left it, but agree with Henry Sipe and you that a good robot is the way to go in West Virginia. By the way I got to know Henry Sipe quite well. He was quite a good influence in West Virginia surveying. He was pretty hard headed about using compasses tho. He never did let go of that and I'll have to say that compasses do work quite well in rural retracement in West Virginia, but most surveyors preferred transits back in those days. Robots would work great but it would be hard to pay for it if one just did rural surveys. The biggest difficulty in West Virginia surveying was making enough to pay the bills. Was why I and many others left.

Over the last few months I've been learning about exporting my points and linework from CAD to kml/kmz format. It's very easy to do in C3d, and I believe it can be done in Carlson just as easily. Your clients in WV might find such a deliverable to be a very useful thing. The sort of thing that would set your service apart. It would help them visualize the layout in a way that makes sense to them.

Creating these kml s is very much facilitated by having your work "on the grid". So while I agree with all that doing RTK in the woods is a non-starter I would encourage you not to give up on GPS and the state plane altogether. Perhaps some static only units, used with OPUS-RS, to put your jobs "on the grid" would be more valuable to you.

Also, keep your eyes open on the performance under canopy issue. With more and more satellites being launched by various countries, and with more L5 capable GPS satellites, there may come a time in the not too distant future when it becomes a reasonable option.

John,

We do a lot of surveying in rural West Virginia and in Western Maryland. We use GPS on almost every large job we do. However, like you said most corners are under canopy and we cannot locate them directly with RTK. The biggest benefit you will see with GPS is that you can establish control or baselines in different areas without having to run traverse in between. We often save a 1/2 day or more of traverse time by establishing control "on the other side of the mountain" in just a few hours. We have procedures developed, (multiple observations, use of OPUS, etc.) that help us verify our control when we do this. I know that our crews would tell you that they couldn't survey without it, although in reality they probably could, they would just have to cut more brush.

However, the best tool that we have for large rural surveys is our sub-meter GPS. We take our sub-meter with us on ALL recon work. In open areas our sub-meter does what it's name implies and gives us sub-meter results, under canopy we typically get results that are +/- 10'-15'. But when you are talking large rural surveys that have 2,000'-3,000' lines the sub-meter gives us good enough results to evaluate evidence. It's amazing how much more effective recon can be when you start with deed plots overlaid on aerial imagery in SPC and a sub-meter unit that you can use to both stakeout to potential corner locations and to locate evidence when you get there. We then have a better idea of what is out there and can develop a game plan to locate that evidence with our TS or RTK. If I could only keep the RTK or the sub-meter for rural surveying, I would probably keep the sub-meter unit.

I also think that you will find that if you do get GPS, you will start to perform all of your surveys based on SPC, at least we did.

MD Surveyor, post: 334353, member: 10081 wrote: John,

We do a lot of surveying in rural West Virginia and in Western Maryland. We use GPS on almost every large job we do. However, like you said most corners are under canopy and we cannot locate them directly with RTK. The biggest benefit you will see with GPS is that you can establish control or baselines in different areas without having to run traverse in between. We often save a 1/2 day or more of traverse time by establishing control "on the other side of the mountain" in just a few hours. We have procedures developed, (multiple observations, use of OPUS, etc.) that help us verify our control when we do this. I know that our crews would tell you that they couldn't survey without it, although in reality they probably could, they would just have to cut more brush.

However, the best tool that we have for large rural surveys is our sub-meter GPS. We take our sub-meter with us on ALL recon work. In open areas our sub-meter does what it's name implies and gives us sub-meter results, under canopy we typically get results that are +/- 10'-15'. But when you are talking large rural surveys that have 2,000'-3,000' lines the sub-meter gives us good enough results to evaluate evidence. It's amazing how much more effective recon can be when you start with deed plots overlaid on aerial imagery in SPC and a sub-meter unit that you can use to both stakeout to potential corner locations and to locate evidence when you get there. We then have a better idea of what is out there and can develop a game plan to locate that evidence with our TS or RTK. If I could only keep the RTK or the sub-meter for rural surveying, I would probably keep the sub-meter unit.

I also think that you will find that if you do get GPS, you will start to perform all of your surveys based on SPC, at least we did.

MD, what kind of sub-meter gps do you use? I'm looking for one.
BTW, I use gps almost every day, sometimes under canopy. I have check procedures that work for me.

MD, what kind of sub-meter gps do you use? I'm looking for one.

Trimble GeoXH with an external antenna.

As others have said, GPS doesn't work well in heavy tree cover. But how heavy is it? If you are kind of on the fringes, it can be used. I've used GPS along with a total station at times. Maybe you start on two GPS points in an open area, run a traverse, and close on another pair of GPS points. I've also done jobs where just maybe one corner was in the trees,you set a pair of GPS points and then shoot the corners in the trees.

As far as state plane coordinates go, thats all I use now. Its not that I want to but in simple terms, GPS likes to work on state plane coordinates and it makes it easier. I've got so many known points around the areas I work now, I usually have a point to start from.

Nobody can tell you "this will work in the woods". Sometimes it might and sometimes it might not. Sometimes it will think it's working and give you the wrong answer. I still see value in it. I have really enjoyed running a network rover, but I also do a lot of static control observations. You can get something that does that fairly cheap.

I don't know exactly what kind of work you do, but suppose you want to survey a job from two sides and be on the same coordinate system. You would have to traverse all the way through without GPS. If you have GPS you can set control on one side and set control on the other and do total station work off both sets of control. It will all be on the same coordinate system when you are working in the office. (Of course I'm presuming you are going to process everything properly and have redundancies to ensure the data is good, but that is one big advantage if you are surveying a large tract.)

No. GPS is extremely frustrating in the woods. Unless you want to establish say, approx, NAD 83 (pick another coord system), otherwise its gonna drive you nuts.

I talked to the salesman again today and he said once the leaves fall off I will be able to use it 100% of the time. I told him I've been talking to other surveyors and that is not what they are telling me. He said, "They must have old equipment or have never used GPS."

So what's up with you guys? 😀

Thanks for all the input and help. I'm going to buy one. I want it to save me time with traversing and it sounds like it will do that. I don't plan on putting away the Total Station.

So you just lean it up against a corner tree to get the shot. Just like with a prism and rod right?;-)

We have done a lot of large tracts in PA. We are one of the few in our area to have GPS capabilities. Lately some of the older firms will sub us out to go out for a day or so and tag their control and tie in their traverse. Yes, there are times when you are frustrated while waiting to fix. But being able to tag monuments on a 400 acre tract in 8-16 hours is worth it IMO. We will often try to push off some of the big stuff until after the leaves drop in the fall. You'll notice a huge difference. Another benefit of putting your jobs in SPC is the ability to maintain and reestablish control many years later with ease. The benefit of being able to download lidars directly into your drawing without a rotation. Having the ability to drop in current imagery along with historical imagery almost effortlessly. We find it very helpful and establishing all of our projects in state plane is always one of our first objectives. As you pick up more and more properties in one area, it is very easy to start developing base mapping for future reference. All properties in proximity are now tied and referenced.
Just some food for thought. It isn't always perfect, sometimes even frustrating but when working, it definitely makes life a little easier.
There might be someone in your area that will demo a unit. We use Trimble and the sales rep came out several times when we were looking and worked with us on some projects in order to get first hand experience before purchasing. An example. We were doing a flood cert and due to all of the bridge replacements, the closest BM was six miles away in either direction. The rep came out and tied into both monuments with a few hundredths in the time it took to drive from one to the other and then established a local BM that we were able to use. Checked in to it three different times over a few days with no issues. We would have never been that close or been able to do the project for a reasonable price if we would have had to run in conventionally.

NO! It's not that easy. Take the salesman to one of your wooded surveys and rerun it again using his GPS unit and compare the results. He better have his best game going on! 😀