Creating a Topo map without a total station

Is there a practical way to create a topo map with say 2-foot contours using a regular laser level or optical transit? My designer would like it around 20 feet outside of the building footprint(50'X50'). Hiring a surveyor is out of my budget. I know how to plot a level line, but capturing all that point data seems like a big task. If I had all of the 3D points at a certain interval I could easily take that into my CAD system to create a 3D surface. Has anyone does this?

Thanks,
Steve

Sure, you just need to come up with a coordinate system or a reference point and assign a z value to your building and start taking shots until you are happy with the surface. How accurate is it? Probably accurate enough for 2 foot contours. Depending on the grades, you may need two shots to several dozen. What is the purpose of the surface?

It's a 2-foot contour. How far would be a reasonable distance along the contour to gather points?
The designer wants to use the elevations for stepping the daylight basement concrete walls, engineering the walls/ retaining walls.

Steve

A 5x5 grid should be small enough to gather enough points to create a model.

10 grids long and 4 grids wide around the building. Kinda the reverse of blue topping.

I wanted to do something similar on a ~9 acre field. I ended up buying a GPS system to do it. If you could find someone with a gps and the site can see the sky, they could knock out what you need in 30 minutes. Using an automatic feature on my gps and the rover mounted to my truck, it auto shot a point every 20’ or something (user defined) and it took 15 minutes to do the field.


With that small of an area you could set your grid up fairly quickly with a couple 100 or 300’ tapes. Collecting the data will take some effort, easier with a laser but a lot of things can read z.

Like lumberjack said it will be easier with a laser.

I would set op the laser on a tripod and shoot a benchmark that is a known elevation if you have one. If not set your BM from a nail in a power pole, fire hydrant, curb at the street, etc. - something that is not going anywhere. Re-shoot your benchmark every time you move your tripod and laser.

Having 2 people will speed up the process, one hold the rod and sliding the receiver and one writing the values down. Shoot each point and write down what the receiver reads on the rod.

When you've collected all the data from the points you can calculate elevation. Take the difference in the rod reading of each point and either add or subtract from the rod reading of the bench mark.

Here's an example:

BM Elevation = 100
Rod reading @ BM= 5

Grid 1
Point Rod reading Difference Elevation
A1 5.05 0.05 100.05
B1 5.75 0.75 100.75
C1 4.85 -0.15 99.85

I can't seem to get the spacing right on the numbers above but you get the drift.

CM1995,

My drawing is a 5-foot grid pattern. I don't see a reason to record the points for the house pushout since it will be flat(daylight basement)? So if I calculate all the X,Y,Z points on a standard Cartesian coordinate system I should be golden? I think surveyors work off of a theoretical flat pane for distances? But in my case, I don't think it will be off by much if I lay my tape measures on the slope of the land?

Steve

We rarely hire a surveyor to do topo surveys unless we have to deal with legal survey stuff and property boundaries. We use a trimble GPS and data collector. Very fast and efficient...provided there isn't tree cover.
Our Trimble dealer rents out our exact setup for a reasonable price. Might be worth checking with yours.

That said, we never pick up a grid like you're describing for our grading plans. We pick up features like top of slope, bottom of slope, trees, swales, fences, ditches, culverts, inverts, building corners, driveways, centerline of road, edge of road, etc. We basically capture the data in the same way it would be drawn. All the points get coded so that whoever is drawing it knows exactly what it is. Works well for us.

DirtyHoe said:

CM1995,

My drawing is a 5-foot grid pattern. I don't see a reason to record the points for the house pushout since it will be flat(daylight basement)? So if I calculate all the X,Y,Z points on a standard Cartesian coordinate system I should be golden? I think surveyors work off of a theoretical flat pane for distances? But in my case, I don't think it will be off by much if I lay my tape measures on the slope of the land?

Steve
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Yep - that's what I had in mind if I were to do it. However I would have 3 people - one person holding the dumb end of the 100' tape, another person pull the smart end tight and have a 3rd mark the grid with a straight edge perpendicular to the tape or a plumb bob. If it's just you then you'll get close enough with laying it on the ground - what other option ya' got?

Used to do them all by hand. 2 guys, a level and a rod. Spend a few hours taking shots then I would plot the shots and draw the contours on paper. I enjoyed doing them.