Back2Basics: Topo field procedure

If in doubt just take more shots. If this is a small pond I would get shots every 25' or so and adjust upward proportionally to the size.

And smaller intervals on the curves.

Dave

What is the purpose of the topo? First decide what your error budget is. Is it going to be a 1' interval? Long, flat curves I would take shots every 30-40'. On sharp curves I might even get shots every 15'. I usually don't hold those distances as gospel. I go by eye and get what I need. Of course, locate anything special or different inbetween. It really depends on how close to reality you need to be. I like to use a "topo boot" or "shoe" to keep the rod from sinking in the mud. Sometimes I make a larger bottom for the boot if the ground is really spongy. I use a plastic 8" plate zip tied or taped to the standard boot.

I like the plastic plate idea!

Dave

> What is the purpose of the topo? First decide what your error budget is. Is it going to be a 1' interval? Long, flat curves I would take shots every 30-40'. On sharp curves I might even get shots every 15'. I usually don't hold those distances as gospel. I go by eye and get what I need. Of course, locate anything special or different inbetween. It really depends on how close to reality you need to be. I like to use a "topo boot" or "shoe" to keep the rod from sinking in the mud. Sometimes I make a larger bottom for the boot if the ground is really spongy. I use a plastic 8" plate zip tied or taped to the standard boot.

Aloha, Donald, Dave and Stacy:

Thank you so much for taking the time to respond!:good: These are valuable suggestions.

Stacy, the purpose is for the future landscaping. Which will done by us too. There are no specific requirements. However, since I am in my infancy state of learning surveying I wanted to develop proper procedures to create good work habits. I was thinking about 1' interval since it will give me much more precise control over the landscape design. I am constantly striving for precision and accuracy more than needed:-) .

Thanks for the Topo shoe idea. It rains a lot here and ground is constantly wet. Didn't know about this until you mentioned it!!

Sounds like a recreational exercise. So pretend you need very tight accuracy. Shoot for 1' interval or 1/2' if the area is really flat. National mapping standards (google it) will help guide you. Use your best guess about distance between shots. If in doubt, take lots of extra shots. Be SURE to locate all breaklines in an organized manner so you can connect the shots correctly. Field check your map. Shoot it all again if you aren't sure. Compare maps. Experience is the best teacher.

> Sounds like a recreational exercise. So pretend you need very tight accuracy. Shoot for 1' interval or 1/2' if the area is really flat. National mapping standards (google it) will help guide you. Use your best guess about distance between shots. If in doubt, take lots of extra shots. Be SURE to locate all breaklines in an organized manner so you can connect the shots correctly. Field check your map. Shoot it all again if you aren't sure. Compare maps. Experience is the best teacher.

Aloha, Stacy:
Thanks for additional details! I will google NMS.

Two more questions…hopefully they don't sound too stupid+o(

1. When you say "shoot for 1' interval" is there a particular distant between the point I should use to collect my field data? Then even closer for flat area? What would you suggest for tight accuracy?

When I say I am aiming for 1' topo, I was think about the settings in my software that will set the interval per user input i.e 2', 5' etc. But I realize the interpolation by the software much more accurate when the points are closer.

2. Breaklines…
I looked it up in ACSM's definition book but I don't really understand what the breaklines are..
The definition of Breaklines: "A linear feature used to define the location where the grade changes between two uniform slopes. In automated mapping, breaklines from the sides of triangles in a TIN"

Correct me if I am wrong…
This is my understudying; Breaklines are edges of the topo contour map where the interpolation are boxed in. When you wrote "locate all break lines in an organized manner" this is to allow me to connect more areas to this map right for future?

Thank you so much Stacy!

There is no specific distance between your shots. The simplest way i know to describe how to tell is this: For a 1' interval topo, if you were to stretch a string from one point to another, there should be less than 0.5' (1/2 the contour interval) between the string and the ground at any point along the string. Does that make sense? Of course, less would be better. I judge it by eye but I've been shooting topo for 30 years.

Breaklines are things such as top of slope, bottom of slope, back of curb, road centerlines, top and bottom of ditches, etc. Imagine shooting a house top. You shoot the ridgeline and edges. The ridgeline is a breakline. That tells the software not to interpolate from edge to edge through the ridgeline. It will interpolate from edge to ridge to edge.

Many methods.

Shoot a horizontal grid with elevations and piece it together in CAD. A good exercise.

Code it in the data collector, taking only the 3 point curve stuff that you decide on right then (pressure! decisions!) and let the CAD draw it. Good for productivity, maybe not for quality Art.

Shoot the critical points by eyeball (points where curves begin, a point on the curve not necessarily the midpoint but close, and the end of the curve. Natural features often have compound curves, and it's important, if you are seeking Art and Realism in your map, to grab a shot everywhere the curvature changes. Later in CAD you can try a few different best-fit 3-point curves and see which points, of the ones you shot, produce the best match for the ground feature.

In CAD you can play with the contour interval. Crank it way down to a third of a foot or a tenth and see how pretty or how jagged that looks. A good way to see if your points are capturing the essence of the ground.

Pretend you are water and flow downhill.

addendum: it's kinda all about the yin and yang of the CAD and the fieldwork. You do the fieldwork thinking, how am I going to use this in CAD? and you do the CAD thinking, "Man, I wish I'd shot that other feature while I was standing there!"

You would probably enjoy some of the web pages out there about botanical garden mapping and arboretum mapping.

Using Carlson commands, I'd define the pond with one "continuous curve", shooting all the major begins and ends of curves.

Without Carlson, I'd probably do the same, but then connect with a polyline in ACAD, and then smooth it.

> There is no specific distance between your shots. The simplest way i know to describe how to tell is this: For a 1' interval topo, if you were to stretch a string from one point to another, there should be less than 0.5' (1/2 the contour interval) between the string and the ground at any point along the string. Does that make sense? Of course, less would be better. I judge it by eye but I've been shooting topo for 30 years.
>
> Breaklines are things such as top of slope, bottom of slope, back of curb, road centerlines, top and bottom of ditches, etc. Imagine shooting a house top. You shoot the ridgeline and edges. The ridgeline is a breakline. That tells the software not to interpolate from edge to edge through the ridgeline. It will interpolate from edge to ridge to edge.

Aloha, Stacy:
I am glad I asked more questions instead of assuming I understood what was shared!!!

Breaklines explanation is perfectly clear! I need to dig into TraversePC on how to apply it--should not be a problem

As for the topo interval…I made a sketch based on your explanation as I understood it. See below
Let say I have 0.3' between string line and ground at location A, then 0.4' at B, 0.5' at C and 0.7' at D. Let's also assume 0.5' at PT# 2 as well.
So I would take shots at PT#1, A, B, C and PT#2 then continue with D etc. spacing the farther apart if flat and closer if the elevation drops faster--but collecting points at every location where the elevation changes within 0.5'. However, I would not shoot anything between C and PT #2. Is this a correct understanding?

Thank you again for taking the time to explain this!

My firm's general rule is if the final scale is to be 1"=30' then get a shot every 30 feet PLUS all "breaks". (A shot an inch at scale as a minimum.)Breaklines are features that will directly impact the contours, such as centerlines of ditches, the water's edge of the pond, tops, toes, retaining walls, etc. These all affect the flow of the contours. Most cad software allows you to set up a Field to finish definition that defines these breaklines and lets you employ 2D and 3D polys to depict them. The 3D breaklines will be used when you buile your surface. The pond will be an "excluded" area in your surface (unless you plan to take soundings and contour the pond bottom.).
Breaklines should also be employed for all man-made features like buildings, edge of pavement, centerline of pavements, edge of concrete walks, curb lines and drainage ditches.

Aloha, James: Thanks…and more questions...

> Many methods.
>
> Shoot a horizontal grid with elevations and piece it together in CAD. A good exercise.
Could you please explain a bit more what this is? I'd love to do this exercise!
>
> Code it in the data collector, taking only the 3 point curve stuff that you decide on right then (pressure! decisions!) and let the CAD draw it. Good for productivity, maybe not for quality Art.
>
I think this is what I want to do initially to get familiar with the process. However, my ultimate goal to have the art quality. Since the monastery grounds in the only project I am working I can focus and put a lot of energy into it.

> Shoot the critical points by eyeball (points where curves begin, a point on the curve not necessarily the midpoint but close, and the end of the curve. Natural features often have compound curves, and it's important, if you are seeking Art and Realism in your map, to grab a shot everywhere the curvature changes. Later in CAD you can try a few different best-fit 3-point curves and see which points, of the ones you shot, produce the best match for the ground feature.
>
Great, this is very, very useful point! Thank you.

> In CAD you can play with the contour interval. Crank it way down to a third of a foot or a tenth and see how pretty or how jagged that looks. A good way to see if your points are capturing the essence of the ground.
>
Will do that.

> Pretend you are water and flow downhill.
>
Start from highest point and work my way down. Got it.

> addendum: it's kinda all about the yin and yang of the CAD and the fieldwork. You do the fieldwork thinking, how am I going to use this in CAD? and you do the CAD thinking, "Man, I wish I'd shot that other feature while I was standing there!"
>
Wow! This happens to me every time I survey. Fortunately, I live where I work:-D But setup and breakdown does take time!

> You would probably enjoy some of the web pages out there about botanical garden mapping and arboretum mapping.
I just googled botanical garden mapping and found tons of images. I am very inspired to create something like this!
or this

> My firm's general rule is if the final scale is to be 1"=30' then get a shot every 30 feet PLUS all "breaks". (A shot an inch at scale as a minimum.)Breaklines are features that will directly impact the contours, such as centerlines of ditches, the water's edge of the pond, tops, toes, retaining walls, etc. These all affect the flow of the contours. Most cad software allows you to set up a Field to finish definition that defines these breaklines and lets you employ 2D and 3D polys to depict them. The 3D breaklines will be used when you buile your surface. The pond will be an "excluded" area in your surface (unless you plan to take soundings and contour the pond bottom.).
> Breaklines should also be employed for all man-made features like buildings, edge of pavement, centerline of pavements, edge of concrete walks, curb lines and drainage ditches.

Aloha, Dent: Trust you are having a great weekend! Thank you for your additional thoughts particularly on breaklines.

Mahalo, yswami!!
If my weekend went any better, it would probably be illegal in 15 states. 😀
From now until the first of next year is my favorite time of the year. I plan on doing a lot of "Ho, Ho, Hoing" and making it all memorable for my grandkids.
I guess one of my Bohemian ancestors must have been one of Santa's elves.

Your imaginary stringline would be stretched along the grade (along the ground) from point to point, not horizontally.

> Mahalo, yswami!!
> If my weekend went any better, it would probably be illegal in 15 states. 😀
> From now until the first of next year is my favorite time of the year. I plan on doing a lot of "Ho, Ho, Hoing" and making it all memorable for my grandkids.
> I guess one of my Bohemian ancestors must have been one of Santa's elves.

Aloha, Dent:
Well...I won't ask how to make it better then. As a monk I probably should't know it anyway!;-)

That's nice. Your grandkids are very fortunate! And I very sure they will have a lot of fun!

Your imaginary stringline would be stretched along the grade (along the ground) from point to point, not horizontally.
Aloha, Stacy: Thank you so much for your patience and forbearance with my questions. I corrected the imaginary line. Otherwise, is my understanding correct?

>

If the measurement from string to ground at point C is close to or more than 0.5' you would take a shot there. That would take care of that segment. If I'm doing a 1' topo, I would take that shot if the ground was 0.3' or more from the "stringline".