# Surveying Methods



## CliffyJ (Apr 29, 2009)

Hi all,

I'm going to be surveying a lot of points out in the yard this spring for my first layout section, and was wondering if anyone had a better surveying technique than the method I used on my retaining walls, and am planning on using for these track-related points. 

My terrain is on a slope, but I'll be using a water level for elevation. So my question relates only to X-Y coordinates, from a fixed point. Also, for the purposes of discussion, let's say that I need precision within a couple of inches.

So here goes with describing what I did for the retaining walls, and was expecting to do for the (concrete) roadbed.

1. From the fixed datum post, I spent a bunch of time locating an X and Y post, say, 40' away, running strings and triangulating with a tape measurer until these strings were perpendicular. These are my main X & Y datum lines. (There are more then one set, but I'll not complicate things).

2. From those strings, I stuck on white duct tape, to shoot a laser against.

3. Using a laser distance finder and tripod, I gradually located a particular point, and plumb-bobbed it down to the dirt.

This method seemed reasonably accurate, but it was very time consuming. And I always had to wait for the wind to die down!

Does anyone have any other / easier / better approaches, that don't involved very expensive gear?

===Cliff


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## jake3404 (Dec 3, 2010)

Use a simple GPS with WAAS capability. I use a Garmin eTrex Vista, it is reasonablly priced and accurate within a couple of inches. The WAAS capability gets it more accurate.

https://buy.garmin.com/shop/shop.do?pID=163&ra=true

Barring that, if you want to still be really accurate. Set up a stick grid. Use wood survey sticks, establish your corner and then measure out 10 ft. I think a 10 foot grid is good enough, or go with a smaller grid if needed. Pound sticks into the ground at each corner of your grid. Then you can use the sticks as markers to measure off to locate your roadbed. You wont have to worry about the wind knocking them over or getting you out of alignment.

Simplest method is get some paint and paint down the track centerline. Not as accurate but you can "get a feel" for how the line will look in full size.


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## rdamurphy (Jan 3, 2008)

CliffyJ, wow, to say the least! Are you going to try to lay a straight line, or do you need to reduce the grade a bit? 

Robert


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## chuck n (Jan 2, 2008)

Your water level is great for grades. To lay out lines, all you really need is a compass and a helper. Start at one corner of the layout and lay a line ( alone a compass sighting). Have your helper pound in stakes along that line (every 4 to 6 feet). Go to the next corner and start a new line. Add or subtract the angle you want to change. Lets say you are going east and you want curve to the north. Your first siting would be (90 degrees, then at the end of that run you would sight a line that is 0 degrees). Repeat the process until you return to the starting place. Once you know the outside shape, you can then fill in the track plan. You can then use the water level to determine the grade changes.

Your corners should be outside the proposed track plan. If you are planning 10 foot diameter curves the corner should be at least 5' past the point where you want to start the curve. You can do this yourself, but you need to sight on a point in the distance and place your stakes along a line between your starting point and the distant object. You could also pound a stake in along that line and stretch a string from that point back to the starting point.


Chuck 




Once you have the angles and distance, you can transfer those measurements paper or a drawing program. 

Or you could outline your proposed layout with stakes and strings and then use a compass and tape to determine the distances and angles.


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## Manco (Jan 5, 2009)

Well my method seems laughable after reading the effort you put it; however it definitely is easier and less time consuming. I find the center point of my radii, and pound a dog stake-out in the ground there. It's got a little swivel attachment for a standard dog chain on top so your"string" isn't getting shorter as it would if you used a traditional stake without a swivel. Then I just stretch out the chain (chain not string because string stretches), mark the chain based on the radius of the particular curve, and then with my inverted marking paint struck through the link of the chain, I just swivel around and paint the ground. Once you have at least two radii laid out, you draw a tangent between the two arcs (I believe that's why straight track is referred to as "tangent" in the prototype) and you continue the steps until you've got your right of way established.


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## CliffyJ (Apr 29, 2009)

Thanks gentlemen for your replies!

Maybe I should clarify the process a bit more. It's a very compact layout, in a tight space. I've worked out all the track geometry based on many rules and guidelines gained from prior discussions here, with people who know far more than I do; and I've distilled all this info on the computer. The result I think, for me, is the need to accurately lay out a bunch of points on undulating soil. If I can do that reasonably well, I think all will work out; if not, well, I'll be using flex track, but I'm trying to stay R5' min on the main line.

The first set of points is what I call the "primaries," because they drive all else. This is, perhaps, similar to what you describe Chuck. Here's an example, showing about 1/5th of the project.











You see here the thick blue main datum lines (with the white tape I described). Using a laser distance finder, I was going to plot out each of the red points, and drive a stake. When done, strings would be run between these stakes.

The next set of points depend on those primaries, so I think of them as "secondaries":










These are also marked with stakes, and strung.

With these points, the arcs can be laid out. The following pic shows radii, which corresponds to a simple template (for spray painting the dirt):











I found that a thin spray-paint line holds up fairly well, even after the storms (that are sure to come for this). But hopefully, working section by section, I'll be able to stake / elevate / excavate for the concrete forms based on all this (using the water level).











Well, that's been my plan at least. As you can see, this method very much hinges on placement of those "primary" points, which are the concern behind my first post. But like I mentioned, the laser / datum method I described is a hassle.

Jake, thanks so much for that Garmin tip. You can bet that link is the next thing I'm going to jump to!

Again, thanks all for your ideas and comments. Best regards,

===Cliffy


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## CliffyJ (Apr 29, 2009)

Posted By Manco on 09 Mar 2011 03:24 PM 
Well my method seems laughable after reading the effort you put it; however it definitely is easier and less time consuming. I find the center point of my radii, and pound a dog stake-out in the ground there. It's got a little swivel attachment for a standard dog chain on top so your"string" isn't getting shorter as it would if you used a traditional stake without a swivel. Then I just stretch out the chain (chain not string because string stretches), mark the chain based on the radius of the particular curve, and then with my inverted marking paint struck through the link of the chain, I just swivel around and paint the ground. Once you have at least two radii laid out, you draw a tangent between the two arcs (I believe that's why straight track is referred to as "tangent" in the prototype) and you continue the steps until you've got your right of way established. Dude! Don't say 'laughable,' you de man who's right in front of me, figuring out all this doo-doo and planting concrete ribbon with all the same concerns that I have. My concrete resides only on my computer, so I'm glad to hear you chime in.

I really appreciate the method you use, especially your idea of chain. Hadn't thought of that.







When I was first laying out my retaining walls, the string stretch became an issue...

Now, I had been originally expecting to use radii _then_ tangents (as you describe), for it just makes more sense: the curves define the geometry, and by planting one point, you get two coordinates (via tangencies with the next curves). 

Other than string stretch though, two things made this method tougher for me (at least in my current knowledge bucket). First, with a sloping site and big bulges of dirt, rock or gravel piles, I couldn't be confident in the arc. Here's a pic of the conditions I was dealing with, in the retaining wall phase:










The tangent _then_ radius approach allowed me to post stakes at defining points, regardless of elevation (just needed to get the X-Y done). After that came the water level and elevation markers, and arc templates used for spraying. Here's how the final wall turned out, on this section.











The terrain still is quite uneven, so I was assuming to use the method I described. However, the terrain might not be so uneven to preclude your radius then tangent approach, because the slope distortion might be negligable, and there are now no obstacles.

Hmmm... gonna have to look into it.

Thank you Sir,

===Cliffy


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## rdamurphy (Jan 3, 2008)

One thing to watch out for is where curves meet tangent track, the absolute best practice is to use easments, if using sectional, and say, you're using 10' diameter, make the last piece a 15' diameter piece. You'd be surprised at how little space it adds and how much of an incredible differnece it makes. 

Also, make sure your curves meet the straights at a right angle, I've seen too many people suffer through too much pain because they "cheated" a couple of degrees and there was a "kink" where the curve meets the straight track... 

Don't be afraid to use fills, cuts, and short bridges and trestles to keep the roadbed perfectly level - or the gradient perfectly even. You'll be glad you did, and it adds so much to the appearance of the railroad. Very few railroads were "laid on the ground" without the earthwork being done right. And none that were intended to last. I would recommend watching some videos of the Cumbres and Toltec on Youtube, to get a feel for how a real live railroad handled terrain that had no flat area within a few hundred miles.

Robert


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## chuck n (Jan 2, 2008)

My recommendation is not to over engineer a garden railroad. Mother Nature hates a perfect track plan and she will not let you keep it. Perhaps if you live in San Diego where the temperature variation isn't much--you're OK, but for the rest of us the track will expand with the heat of the summer and contract in the cold of the winter. You already have your pad on which you are planning to lay your track, now just lay your outside mainline with the switches. Everything thing else will then fall into place. When the track is down mark the location and then remove it and trench along the route to add ballast and level. If you are like the rest of us, you will be, over time, making changes to the track plan. Give it time to evolve.

Chuck


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## CliffyJ (Apr 29, 2009)

Posted By rdamurphy on 09 Mar 2011 06:16 PM 
One thing to watch out for is where curves meet tangent track, the absolute best practice is to use easments, if using sectional, and say, you're using 10' diameter, make the last piece a 15' diameter piece. You'd be surprised at how little space it adds and how much of an incredible differnece it makes. 

Also, make sure your curves meet the straights at a right angle, I've seen too many people suffer through too much pain because they "cheated" a couple of degrees and there was a "kink" where the curve meets the straight track... 

Don't be afraid to use fills, cuts, and short bridges and trestles to keep the roadbed perfectly level - or the gradient perfectly even. You'll be glad you did, and it adds so much to the appearance of the railroad. Very few railroads were "laid on the ground" without the earthwork being done right. And none that were intended to last. I would recommend watching some videos of the Cumbres and Toltec on Youtube, to get a feel for how a real live railroad handled terrain that had no flat area within a few hundred miles.

Robert 
Thanks for the reply Robert.

I'll be using flex (from Train Li), no sectional. But I appreciate your point. It'll be difficult to bend things perfectly. I haven't considered transition curves due to the extra complications, but hopefully things will work out with the bender and clamping and adjusting. And making the concrete roadbed forms transition as well. We'll see.

Yes, I'll be using lots of fills, cuts, bridges... the final earthwork surface will be shaped to suit. The pic's might look like this is a flat surface, but it's not; nor will it end up being, once the final "terra forming" happens. 

Regards,
===Cliff


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## CliffyJ (Apr 29, 2009)

Posted By jake3404 on 08 Mar 2011 05:17 PM 
Use a simple GPS with WAAS capability. I use a Garmin eTrex Vista, it is reasonablly priced and accurate within a couple of inches. The WAAS capability gets it more accurate.

https://buy.garmin.com/shop/shop.do?pID=163&ra=true

Barring that, if you want to still be really accurate. Set up a stick grid. Use wood survey sticks, establish your corner and then measure out 10 ft. I think a 10 foot grid is good enough, or go with a smaller grid if needed. Pound sticks into the ground at each corner of your grid. Then you can use the sticks as markers to measure off to locate your roadbed. You wont have to worry about the wind knocking them over or getting you out of alignment.

Simplest method is get some paint and paint down the track centerline. Not as accurate but you can "get a feel" for how the line will look in full size.
Hi Jake, I looked up that product and had a couple of questions for you. 

With the WAAS option, they talk about accuracy being good to a couple meters, not inches. But if you use it in a localized sense, do the coordinates remain relatively stable / accurate? Is that what you mean?

Also, they say the thing's discontinued, but are you aware of a superceding product?

Thanks guy,

===Cliffy


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## chuck n (Jan 2, 2008)

Cliff:

I have a Delorme GPS with WAAS and it is good to several meters (most of the time). I think that to get to surveyors precision with a GPS you have to be licensed, with federal approval. The signals for typical GPSs are degraded by the government for security reasons. Military, surveyors, and some scientists (geologists and geophysicists) can get units to mm accuracy. But these aren't available to the general public.


I have heard that if you take multiple readings at the same point and average the results you can improve the location accuracy, but I haven't tried it. Perhaps if you sat on the same point for several minutes, you would improve the accuracy. 


Chuck


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## CliffyJ (Apr 29, 2009)

Thanks for that fascinating bit of back-story, Chuck; I'd no idea. Living near a major security-requiring institution, that sort of thing makes sense, and comports with other things I've experienced. 

Thanks also for those other items you spoke of. 

I'd been hoping that someone knew of an affordable product where you put two or three little transmitters around the property, and had a handheld device which triangulated between. But I've not seen any. Or at least, I've not plugged in the proper search terms. 

===Cliffy


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## armorsmith (Jun 1, 2008)

Cliff, 

Might I make another suggestion - provided you have a table saw. Rip thin pieces of 2 x 4 - 1/4-3/8" x 1 1/2. Join these pieces end to end and use this flexible spline and garden stakes to layout your route. This will provide nice and easy transitions, considering you are going to use flex track. The safety fall back is to cut a piece of 1/8" masonite hardboard to the minimum radius you plan to have on your railroad and check the spline to be sure you have not gotten below your minimum. Where ever you are going to have a switch, screw a piece of 2 x 4 to the spline to keep it straight If the ripped 2 x is too stiff, use pieces of the masonite, it will be even more flexible. I will be using fixed radius - all 20 foot diameter - so I will be doing the kind of surveying you are talking about, but I am in Florida with almost level ground. 

Bob C.


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## chuck n (Jan 2, 2008)

Cliffy:

I've been thinking about your wish for a triangulation hope ( inexpensive). Place two stakes in the ground that extend beyond the boundaries of the layout. With a tape measure carefully measure the distance between the two stakes. A compass line between the two might be helpful, but maybe not. With those two stakes and a tape measure you can triangulate to any point. If you put a stake in the layout you can measure the distance from each stake draw a arc from each stake (primary two points) on your base, paper or computer. The two circles will will intersect. One will be on the track plan and the other will be off. Using this may give you the detail you need.


Chuck


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## CliffyJ (Apr 29, 2009)

Posted By rdamurphy on 09 Mar 2011 06:16 PM 
...
Don't be afraid to use fills, cuts, and short bridges and trestles to keep the roadbed perfectly level ...
Robert 
I should have noted, Robert, that in the fourth diagram the thick gray bars represented trestle piers, and the rectangles arrayed around certain arcs represent concrete blocks lining tunnels. Here's a rough portrayal of the layout. The design has changed in many details, but it's close. The pics and diagrams I've posted relate to the left/lower section of this pic:










As you can see, space is very tight. 

Many people here on this forum have helped me, an ignorant newbie, to work through the roadbed and track geometry issues; and I'll be happy to cite those threads here, if anyone wishes to plow through their teaching of my ignorant big behind. 

But as things stand, I'm gonna plant my concrete ribbon, per the plans I have. And if anyone wishes to hear about the very many geometry rules that I've accumulated per the wisdom of others on this site, please let me know. 

I'll be employing concrete roadbed. And that means accurate surveying of key points, which is what I posted about.

I'm not intending to over-engineer. As a professional designer, believe me, I get that accusation from my various managers when the budgets get tight. But here, on my turf, where the space is tight and the turnouts cost over $170 each and I don't want the trains to constantly derail, you can bet that I'll do my best to get the fricken driving geometry correct, before I pour my concrete roadbed. 

All I'm doing (in this thread) is asking for your help, in getting those X-Y points positioned correctly on an undulating terrain.

Best regards, and I hope I'm not sounding too pissy or sassy or bossy,

Probably am, but I'll buy you a beer if I went over the line,

===Cliffy


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## afinegan (Jan 2, 2008)

Wow, looks like a dream layout! I would love to have something like this (with huge curves though) when I retire! 

I am sure you will figure it out and the plan will come together, don't forget to fill us in!


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## chrisb (Jan 3, 2008)

Modern Surveying is based on x, y and z coordinates or N, E and elevation. The process is called COGO or coordinate geometry. Alignment with ciculair and spiral curves between tangent section still apply in design but the field layout 
is done by coodinates. Contol ponits set set by GPS and I don't mean a garmin with Waas. Then a total station and a handheld computer (data collector) with a survey software are used for layout. 
Archelogists use a string grid to "survey" or collect data. The string grid will give you x any y for horizaontal control. If the strings are all level it will also give you Z. The string line grid should help u rough things in pretty close. 
Same idea as batter boards. You sould be able to get the x and y data from your drawing program.


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## jake3404 (Dec 3, 2010)

Sorry Cliff, 
I didnt check to see if the Garmin is still being made. I bought mine a few years ago and it works pretty good. As far accuracy goes you have a few things. You can get more accurate, but it will be outside your budget. I used to use a Topcon Trimble that gets you down to within a inch. But this system costs a lot. It uses a known surveyed point (which means paying a survey company to establish it, $$$) and then a base station set there and a mobile station that triangulates. Anyways, if I remember your looking at about a $10,000 - $15,000 bill. 

The WAAS capability does make your GPS more accurate then advertised. WAAS (Wide Area Augmentation System) means there are two geosyncrinous (spelling?) satellites that are in the western and eastern horizons of the US. WAAS enabled GPS use these satelites to tragulate their position with the normal GPS sats to get a much more accurate reading. Even though a commerical GPS system says they can get with a foot or two you can acually get them closer. 

Here is what you do, go to the point you are trying to survey in. Put your GPS on the ground. Let it set there for about 5 mins. The WAAS updates about every 5 seconds. Your little GPS will take those readings and average them out. If the GPS unit sits there long enough then the average balances out to a very accurate reading. When I was a full time Mining Engineer I used this capability many times to survey out points in the mines I was working in. Many times those points would get checked by a professional survey crew or with an expensive Trimble and I found that I was within an inch or two. 

As far as the GPS unit to buy... there are a lot of good quality ones at a pretty good price. Be carful not to buy one the the cheap ones. The antenna in the unit makes a difference and the more expensive ones have better antennas. A garmin or megellan are good units. Make sure it is WAAS capable. 

Another little trick there were more satellites in my area in the morning. So I tried to survey in the morning. The more satellites you are connected to, the more accurate you are.


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## chrisb (Jan 3, 2008)

I thought waas somehow combined a ground signal but I may be wrong. i would think that a gps set to UTM or MGRS is only going to give you a 10 digit grid coordiate. That gets you to 1 meter. 
Sting line is the way to go.


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## jake3404 (Dec 3, 2010)

Yes it uses a ground signal to establish a exact loaction of the satelite in the sky. That is updated every 5 seconds. This update with a known point in the sky along with the triangulation of the other normal GPS satelites in the sky give you an accurate reading. Trangulation with a known point, which is what WAAS is accomplishing, gives you a good reading, then combine that with a faily stable point (leaving the unit sit for about 5 mins) and you get even more accurate point. I know what your thinking and in theory your right chris. But in practice as I have done many times as I described and it does work. And I have verified it with an expensive Trimble system. 

In the end I agree with your solution of a string line grid is more simpler. I noted to eliminate the strings and just use stakes to establish corners of your grid and then measure off those stakes to get your locations on the layout.


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## CliffyJ (Apr 29, 2009)

Posted By armorsmith on 10 Mar 2011 07:24 PM 
Cliff, 

Might I make another suggestion - provided you have a table saw. Rip thin pieces of 2 x 4 - 1/4-3/8" x 1 1/2. Join these pieces end to end and use this flexible spline and garden stakes to layout your route. This will provide nice and easy transitions, considering you are going to use flex track. The safety fall back is to cut a piece of 1/8" masonite hardboard to the minimum radius you plan to have on your railroad and check the spline to be sure you have not gotten below your minimum. Where ever you are going to have a switch, screw a piece of 2 x 4 to the spline to keep it straight If the ripped 2 x is too stiff, use pieces of the masonite, it will be even more flexible. I will be using fixed radius - all 20 foot diameter - so I will be doing the kind of surveying you are talking about, but I am in Florida with almost level ground. 

Bob C. Hi Bob,
Yes indeed! That's exactly how I'm planning on running the forms for the concrete (1/4" masonite). So I appreciate that bit of confirmation! 
Your idea on the template is very good. I'd been imagining several "hard" templates for varying radii, but the thought of only worrying about the minimum (in my case, R5' for mainline, R4' for spurs) is excellent.
Thank you Sir,
Cliff


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## CliffyJ (Apr 29, 2009)

Posted By chuck n on 10 Mar 2011 07:46 PM 
Cliffy:

I've been thinking about your wish for a triangulation hope ( inexpensive). Place two stakes in the ground that extend beyond the boundaries of the layout. With a tape measure carefully measure the distance between the two stakes. A compass line between the two might be helpful, but maybe not. With those two stakes and a tape measure you can triangulate to any point. If you put a stake in the layout you can measure the distance from each stake draw a arc from each stake (primary two points) on your base, paper or computer. The two circles will will intersect. One will be on the track plan and the other will be off. Using this may give you the detail you need.


Chuck 


Roger that Chuck, that's how I did my initial surveys for the deck (or observation platform) in the middle, to get positions of trees and things. I kept messing up though (up to a foot), mainly due to tape sag. That is, I felt quite confident in the triangulation, until I tried getting the same coordinate from two others (as a check). 

Even so, all great points, I'm positive that your method works, as long as the tape is pulled tightly! 

Thanks, and regards,

===Cliffy


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## CliffyJ (Apr 29, 2009)

Posted By afinegan on 11 Mar 2011 08:51 AM 
Wow, looks like a dream layout! I would love to have something like this (with huge curves though) when I retire! 

I am sure you will figure it out and the plan will come together, don't forget to fill us in! Very kind of you, Sir!

You've got some pretty amazing benchwork there. It reminds me of how I first planned on doing this: all raised on benchwork, with the ability to walk beneath it. Ironically, that notion drove all the excavation: the lower tier was the access area and the layout was supposed to start there -- and not wrap around the house! But fortunately, my wife was able to finally talk some sense into me. (It would have taken miles of expensive lumber, for starters)(and probably a couple of slipped disks!).

Even so, I'll have to check out your site, your work looks awesome!

===Cliffy


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## jimtyp (Jan 2, 2008)

Cliffy, that looks awesome!


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## CliffyJ (Apr 29, 2009)

Posted By jake3404 on 11 Mar 2011 09:17 AM 
Sorry Cliff, 
I didnt check to see if the Garmin is still being made. I bought mine a few years ago and it works pretty good. As far accuracy goes you have a few things. You can get more accurate, but it will be outside your budget. I used to use a Topcon Trimble that gets you down to within a inch. But this system costs a lot. It uses a known surveyed point (which means paying a survey company to establish it, $$$) and then a base station set there and a mobile station that triangulates. Anyways, if I remember your looking at about a $10,000 - $15,000 bill. 

The WAAS capability does make your GPS more accurate then advertised. WAAS (Wide Area Augmentation System) means there are two geosyncrinous (spelling?) satellites that are in the western and eastern horizons of the US. WAAS enabled GPS use these satelites to tragulate their position with the normal GPS sats to get a much more accurate reading. Even though a commerical GPS system says they can get with a foot or two you can acually get them closer. 

Here is what you do, go to the point you are trying to survey in. Put your GPS on the ground. Let it set there for about 5 mins. The WAAS updates about every 5 seconds. Your little GPS will take those readings and average them out. If the GPS unit sits there long enough then the average balances out to a very accurate reading. When I was a full time Mining Engineer I used this capability many times to survey out points in the mines I was working in. Many times those points would get checked by a professional survey crew or with an expensive Trimble and I found that I was within an inch or two. 

As far as the GPS unit to buy... there are a lot of good quality ones at a pretty good price. Be carful not to buy one the the cheap ones. The antenna in the unit makes a difference and the more expensive ones have better antennas. A garmin or megellan are good units. Make sure it is WAAS capable. 

Another little trick there were more satellites in my area in the morning. So I tried to survey in the morning. The more satellites you are connected to, the more accurate you are. Hi Jake, thanks for that engineering background, you de man. 

After posting last night, I found that Trimble unit... then I finally found the price... *gulp*! Even on ebay, ~$2k for the handheld... So yeah, so much for that!

I love your tip on waiting for the commercial GPS unit to get the average, I would've been in too much of a rush to figure that one out. Your other points are excellent as well, as usual.

Perhaps the best thing might be to just get it, and see how things check out vs. manual / laser methods. Besides, I can always use it around the property. Be nice to know, for example, roughyl where all the big trees are, in the future expansion areas...









Take care,
===Cliff


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## CliffyJ (Apr 29, 2009)

Posted By jimtyp on 11 Mar 2011 02:59 PM 
Cliffy, that looks awesome! Thanks, Jim! I appreciate that!


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## chuck n (Jan 2, 2008)

Cliff:

If you are worried about stretching the tape and it sagging, you could put in a couple of extra stakes that are closer together along a straight line, so that your longest stretch wouldn't be more than 10 or 15 feet. Another possibility would be to get a spring scale (like the kind used to weigh fish) in a sporting goods store. This would require two people. For each measurement you would pull the tape to the same tension, say 20 pounds. I think that this is what surveyors used before GPS.


For a long stretch of the tape you could put a chair or two or some other objects along the length to help support it and minimize the sag. 




Chuck


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## CliffyJ (Apr 29, 2009)

Posted By chuck n on 11 Mar 2011 03:13 PM 
Cliff:

If you are worried about stretching the tape and it sagging, you could put in a couple of extra stakes that are closer together along a straight line, so that your longest stretch wouldn't be more than 10 or 15 feet. Another possibility would be to get a spring scale (like the kind used to weigh fish) in a sporting goods store. This would require two people. For each measurement you would pull the tape to the same tension, say 20 pounds. I think that this is what surveyors used before GPS.


For a long stretch of the tape you could put a chair or two or some other objects along the length to help support it and minimize the sag. 




Chuck 


Hi Chuck,

Yes, all very true, and thank you Sir. But for a one-man operation, the laser distance finder worked wonders. The two (actually three) datum lines I used have the white duct tape; and by pivoting the DF at the intended point location, I was able to get (I think) fairly repeatable coordinates. 

I should point out that when taking a measurement from one or the other datum, I kept sweeping the laser dot on the tape until the reading was the smallest possible, which mean I was roughly perpendicular to the datum line. Then I pivoted to the other line, and did the same. And so on, until the reading was what was intended from both axes.

As I found with the retaining wall build though, this is by no means a fool-proof approach. The main issues I encountered were as follows:
1. Wind (blowing the datum line, because the duct tape acts like a sail) 
2. Amount of time it takes to get one point (back-and-forth measurements between the two datums)
3. Possible (probable?) inaccuracy of the main datum strings (which rely on tall stakes, located by other means; and if these are off, the whole she-bang is off!)

In a very real sense, I'm agreeing with all the ideas you've posted, but with a laser measuring device, and in reverse: two virtual circles radiating from the DF, with known radii, intersecting the two datum "planes". No other strings are involved, except that for the plumb bob to mark where the "primary" stake should go.


Thank you Sir, and best regards,

===Cliffy


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## jake3404 (Dec 3, 2010)

One last thing I can tell you about surveying. "Back in the day" they didnt have fancy stuff to survey. My family's large ranch was done with a compass and a chain. The chain because like you they were concerned about strech, chain does not strech. A few years ago were had an aerel (sp?) survey done and the chain and compass method used many, many years ago was very accurate. 

So instead of a string or tape, use a premeasured length of chain.


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## CliffyJ (Apr 29, 2009)

Posted By jake3404 on 12 Mar 2011 08:15 AM 
One last thing I can tell you about surveying. "Back in the day" they didnt have fancy stuff to survey. My family's large ranch was done with a compass and a chain. The chain because like you they were concerned about strech, chain does not strech. A few years ago were had an aerel (sp?) survey done and the chain and compass method used many, many years ago was very accurate. 

So instead of a string or tape, use a premeasured length of chain. Hey Jake,

It always awes me on what they did with those chains, poles, and simple barometric altimeters. The survey / topo maps I'm working with (for Virginia City, NV), and others, have their BM's (benchmarks, I think the term refers to) based upon all that hard work, gained by boots on the ground. 

So like you, I really respect the efforts of those guys. 

But for now, being a one-man operation, I'll stick with the laser method I've described. Chains sag more than tape, and I can only be in one place at a time. Could you comment on the method I've spoken of? It worked pretty well, but it has those weaknesses I listed.

I thank you again for your great info on the GPS units, and how to get more accuracy from them. But they're pricey (~$500 for the higher-precision Garmins), so maybe I'll put that acquistion off a bit. Would love to have it, but accumulating the funds for the switches and rail is proving to be a challenge. 

Best regards Sir,
===Cliffy


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## Gary Armitstead (Jan 2, 2008)

Posted By jake3404 on 12 Mar 2011 08:15 AM 
One last thing I can tell you about surveying. "Back in the day" they didnt have fancy stuff to survey. My family's large ranch was done with a compass and a chain. The chain because like you they were concerned about strech, chain does not strech. A few years ago were had an aerel (sp?) survey done and the chain and compass method used many, many years ago was very accurate. 

So instead of a string or tape, use a premeasured length of chain. 

That's where the surveyor's term "chaining" comes to play. Fifty years ago, my first summer out of high school, I worked for the Bureau of Reclamation as a "trainee" surveyor. Doing chaining then brought a whole new meaning to gopher(go-fer) work.


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## jake3404 (Dec 3, 2010)

To critique your method...


I think it is going to be pretty accurate for you.


I do think that you should establish a grid with wood stakes. Then use the stakes as your reference points for measuring. The smaller distances mean that the wind and strech will be less. Plus you can trangulate from more than one location reference point to get a more accurate measurement. I never surveyed a lot but one thing I did know was to always trangulate to get accurate. Survey the same point from more than one reference location.
As for the GPS here is a good one for a good price. GPS It is from the Garmin website, but I think you might be able to get it for cheaper from a discount retailer.


One last thing, your method of establishing elevation with a water level is good. But you can be even more accurate with your laser level. Make a "stadia Rod" using a stick with 1" or less marks on it. Use the laser as a transit and I think your elevations are going to be even more accurate than the water level.

Finally, I think someone else said it, but it deserves repeating. Do all your marking and surveying. Then put your track together and lay it over your marks. Ultimately it is the track your trying to accomidate. Then adjust your lines and remark the ground. Then start excavating to make your concrete ribbon.


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## RimfireJim (Mar 25, 2009)

Cliffy, 
I think your method is fundamentally sound. I think your #1 drawback is having to do it all by yourself. This is a classic case of where having two people makes a job go more than twice as fast. Isn't there anybody you can get to help you, even if you need to hire them? Neighbor kid? All they have to know how to do is hold what I call the "dumb end" of the tape, string, whatever. Even today, with all the fancy equipment, surveying is still a two person job (based on my observations of survey crews I see out and about). 
As far as reducing the iteration time for establishing your primary points off the datums which are flapping in the breeze, you might be better off working out the distances to fixed points, e.g. datum intersections, and using those instead. Bearings at right angles will give you the most accuracy, but there is plenty of latitude to depart from that, and you can always check to a third point or to your datum lines. One thing I don't know is how well the laser distance finder will pick up a round (omnidirectional) reflector, which is what you would want at the fixed points.


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## RimfireJim (Mar 25, 2009)

Use the laser as a transit and I think your elevations are going to be even more accurate than the water level. 
Probably not, unless you have a relatively expensive laser level. With a water level you can easily get within +/-1/8" over practically any distance, whereas many laser levels are 1/4"/100ft or worse. Of course, the drawback to a water level is that it is much, much easier with two people. Besides, he didn't say he had a laser level, just a laser distance finder.


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## jake3404 (Dec 3, 2010)

Ah, right good catch. I assumed the laser level.


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## CliffyJ (Apr 29, 2009)

Thanks guys, all great points. 

Based on that, yeah, I'll look into seeing if a few of my deck posts are good candidates for string or chain -based triangulation. I can picture a lightweight chain secured to a (split / re-assembleable) tube, maybe pvc, so it can swivel at the post. Foot marks on the chains; 1" or 1/2" links. Then holding those two chains, walking them out to the 2 desired radii, and planting the stake. 

All depends on how well I can map the datum posts, but I suppose I can use the same method (for mutual triangulation). 

Also, your comments about laser leveling remind me of a rotating version, which I had a chance to borrow from work a couple years ago. It was mainly good at dusk, but wow, it was sweet! There's a chance I could borrow that baby again... If not, I might snag our regular laser level. 

Yes, it's tough to get help out here; few neighbors, and my kids are away at school. Mom's hugely busy, so... your points on one-man op's are very appreciated! 

Best regards, and thanks again, 

===Cliffy


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