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LyleBrowning

3D solid from survey points

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I do archaeology for a living and am about to embark on a large urban excavation where large numbers of stratigraphic units of non-uniform shape will be excavated. Typically, these are measured in a single-context system wherein the outer perimeter is mapped and the shape of the layer is also recorded. I've used VW for years to accomplish my work and now want to extend it a bit.

Also, I'm looking at buying a total station to record the info from the site and upload it into VW for graphic display. What I need to create are layers, features such as walls (wall tool or extruded rectangle), Postholes (extruded rectangles or cylinders) and pits (arc tool), etc.

My question is whether VW can create a 3d shape from a set of

coordinates and elevations such that I can re-create the layers and have a virtual excavation later as part of the public presentation. I've done 3d modeling of timber framed barns but that is just a matter of creating extruded rectangles and manipulating them into position.

On the site, I can create a wall as an extruded rectangle, or as a wall, depending upon how I choose to do it. A flat layer, such as the top layer of asphalt on the site is also an easy extrude, but how does one do, for instance, a flattish bowl shaped layer that is not evenly flat on top and is not uniformly curving from a center deep point? I have done it the hard way by subtracting solids but with the total

station, is there a way in VW to create the 3d solid from the info it provides? Imagine an inverted umbrella infilled and with a side dented and that's a pit feature.

I have VW-09 on a MacBook Pro.

Thanks in advance,

Lyle Browning

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Lyle, while I'm not an expert in this exact type of task, I would think it could be accomplished fairly easily, as long as the chosen methodology was rigorously applied.

One answer to your specific question is that yes, using even a simple 3d modeling tool like the 3d polygon, one can connect the dots of any planar 3d object. Curved 3d surfaces can be created with nurbs. Etc. etc.

I think the real question is whether there is a way to automate, or at least partially automate the process within Vectorworks. If you look at the way the Site Model tool works (and also at it's limitations) I think it might lead you to an understanding of how to proceed.

For this type of specialized task I would look for someone who might be able to write some Vectorscript (or other plug in code) to help out.

As an Anthro major in college (and a long time VW's user) I am quite interested in the results. Keep us posted.

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Hi

This is quite a timely question as I bought a Total Station a couple of weeks ago.

I had the option of spending ??? on a program to take my TS data and convert it into dxf that is then imported, or write my own.

I am currently writing my own and have developed a methodology that I use when surveying with the TS - I am not a trained surveyor so I am doing this all from scratch to suit my needs - it may not be the recognised way of doing things.

Unfortunately I have found a couple of bugs in VW that is currently causing me to create work arounds, however, my work flow is basically this:

Undertake survey with TS. Record points using a set of prefixes for the point ID. This is key to logically grouping points. Another method would be to use codes for each point, but this method does not give me a one line solution for each point.

After surveying, import TS data points into data collector in ID, E, N, Ele, Desc format. Due to bug in VW, the point ID is actually part of the description. This description also includes the reflector height - my TS is reflectorless so I some points I durvey by laser, others by rod. If surveying data that contains ground levels, then elevation data is ignored if I am using laser (reflector height = 0.0) as I for example are just picking off points with a random elevation say off a wall corner so the elevation is not meaningful, however, if I use the rod, then the elevation is mostly meaningful at it is the ground level. This varies on an object by object basis as for instance, windows will have meaningful elevation measurements.

I then import the ID, N, E, Desc data into Vectorworks using the import survey data. This tool has a bug so does not import ID's in an alpha numeric format. This creates 3D stake objects.

I then run a script that read each stake and correctly populates the ID prefix and number. It also does a few other things that are in flux at the moment, such putting the stakes into appropriate classes.

I now have a script that allows me to select all stakes of similar ID prefix. So this is basically selecting all stakes what were appropriately grouped using the point ID at the time the survey was undertaken.

I then have a script that creates 2D and if appropriate 3D polygons from the selected stakes - it basically joins the dots.

That is currently where I am at. What I end up is a drawing whereby I can fairly quickly creates areas and lines. I can then massage the polygons, such as adjusting or creating points which I did not measure, such as obscured corners of walls or posts. Once I have the correct polygons, it is then a relatively simple matter of creating the appropriate closed solid and extruding if need be.

Key to my method is initial grouping of points and working in a logical manner with a sequential point id as this governs the order that 'dots' are joined.

There is however still quite some manual intervention needed but what my tools do assist greatly in is the ability to create logical polygons from a mess of points in 3D space.

But I still have quite a bit of work still to do on my tools to extract meaningful relationships from the original points.

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It's really not all that difficult... been doin it for at least 20yrs now.

Just a matter of getting the Total Station XYZ data ... making a few conversions and then using the power of DTM to connect the dots.

Here's a link to an olde but still useful example vectorscript...

CAD Site Survey VSS+DTM example

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I really like seeing this conversation, as I just had a chance to visit with a potential reseller who also sells/rents GPS input devices that can take the data, as well as allow you to enter field discernment of what the points mean, including the trees and their conditions, etc. The workflow then involves exporting those points in a DXF file, which can be brought into Vectorworks (Landmark)and the points, with their associated data records, come in like a charm. Seeing this, I do say there would need to be a script to then turn the collective points with specific records (ie lamppost, tree, bench) into a premade symbol. We have been having some discussion about this since and expect to have something to say in the near future to help with the site data collection and plan establishment. Keep up the talk on this. I would like to see what each of you have to say on this topic.

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Thanks to all who have replied thus far. What I have seen and infer from discussion is essentially a single 3D object. Archaeological sites are essentially layer cakes, but the layers of the cake are not uniform at all. They slope which VW can handle. They have uneven upper surfaces, which VW can also handle. It's the uneven bottom surface that's the issue. VW can handle a perimeter set of points and can model the top surface but the question is can it also on the same solid, show the bottom surface accurately? If the survey data comes in as a DXF file, then it should work after rendering.

Part of what I want to do is to show standard profiles through layers which Landmark can do. Next I want to take layers and separate them vertically and show them in isometric view so that their relationships to layers that a single layer touches can be visible for illustrating our typically arcane arguments about temporal affiliation and spatial relationship.

As I would be bringing in survey point groups daily, conversion time is going to be an issue. I had hoped that with a DXF file and a small amount of fiddling about, I could get something out for the next morning's excavation aids.

Any thoughts or am I in cloud cuckoo land?

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Islandmon

Whilst dtm is great for levels, what about solids such as buildings, steps, windows, posts etc? Surely you need to associate these points with each other? Levels is straight forward as its simply a point in X,Y,Z space and there is no need to associate it with any other, but having a pair of 4 X,Y,Z coordinates in 3D space can mean to many different things such as windows, doors, steps, post etc etc etc. How do you associate these so they form for instance a rectangle that represents a window, or a surface that represents a step?

Eric

I am new to total stations having bought a refurbished Leica Total Station a couple of weeks back. For me, its a steep learning curve both in using the machine, recording survey points and remembering to do things rather than doing things intuitively.

My TS allows codes to be input that can be associated with points. Its an extra stage in the surveying process. I already set up codes for me, such as Tree species, spread etc. Unfortunately for me, with my Leica, whilst the codes are associated with points, they do not export (or at least I have not found a way to) with the measurement data and merely output as a separate recording on the previous line. So this does mean that at present, when I import site survey data, I cannot simultaneously import the codes. However, due to the bugs that I have found and reported in Import Survey Data and in the stake object tool (when selecting 'show as 2D graphic only' the X, Y, Z data is not returned correctly by the VS function get3dcntr nor display correctly by the stake object when displaying elevation data), I am thinking about writing my own import function that will pick off code information supplied from the TS at time of recording.

The ability to record survey information at the point of survey is not rocket science which is why I have developed my own very basic tools to provide associations between the hundreds of 3D points that are generated when surveying. My method, no matter how basic, whilst still developing, uses simple mnemonic codes and a running sequence number and works extremely well, even though it is basically X,Y,Z,descrip data with the descrip holding the point data mnemonic and sequence number. With more information about the point, such as available using data codes, is definitely the way forward. However where I see it tricky is in the many different ways that it is possible to export data from even a single model TS. It would be great however to see TS data association support built into VW if this was possible and good to see interest from NNA on the topic.

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Ian,

Objects embedded or on top of the earth surface should not be part of the DTM. Only their x,y,z location at the surface should be recorded. Their dimensions and other characteristics can be included in the description field. There is a degree of engineering judgement as to what is part of the natural terrain. Roads, curbs, sidewalks, steps, driveways should be included while buildings, signs, trees should only include data at the ground level. I once generated a DTM that had spikes 7 feet high and could not understand why it was showing this way. When I checked the survey points, it turned out to be signs with the elevation at the top of the post rather than the bottom.

We use sokia equipment for surveying and all I ask is for a text file with the ID, code, description, and location for each point.

As some of you have experienced, the VW import survey has its limitations so I had to write a custom import and also a survey/stake object to hold all the information. Since some of the codes used by the surveyors are uniform, the import survey script recognizes this and inserts the appropriate symbol for the objects such as trees, signs, power poles, valves, meters, manholes, etc.

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VW can handle a perimeter set of points and can model the top surface but the question is can it also on the same solid, show the bottom surface accurately?

The question is how do you measure the 'bottom surface' of an archeological strata

without first removing all the upper layers prior to surveying the bottom topography.

One way is to use ground penetrating radar ... is that what you are doing?

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Islandmon

Whilst dtm is great for levels, what about solids such as buildings, steps, windows, posts etc? Surely you need to associate these points with each other? Levels is straight forward as its simply a point in X,Y,Z space and there is no need to associate it with any other, but having a pair of 4 X,Y,Z coordinates in 3D space can mean to many different things such as windows, doors, steps, post etc etc etc. How do you associate these so they form for instance a rectangle that represents a window, or a surface that represents a step?

DTM does not like overlapping data points when creating a surface. But it is possible to extrapolate between data surface layers by addition & subtraction. And it is possible to rotate the data plane to any XYZIJK orientation imaginable. Once the surfaces are described they can be combined to form 'solids'.

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VW can handle a perimeter set of points and can model the top surface but the question is can it also on the same solid, show the bottom surface accurately?

The question is how do you measure the 'bottom surface' of an archeological strata

without first removing all the upper layers prior to surveying the bottom topography.

One way is to use ground penetrating radar ... is that what you are doing?

We do single context recording which is basically excavation by trowel, one layer at a time. We will record the top and extent of the layer, excavate it and then record its bottom shape as well, which may be one or multiple different layers that it formerly lay upon. So yes, we would remove the layers above the one in question.

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Eric the most simple way to input the collected land survey 3D point data (ID, Y, X , Z, Description or code) is a Comma Spaced Values format (CSV) since it allow the user to review, edit and modify these values easily in MS EXCEL worksheet prior to importing them into VW09 and generate the DTM (LandMark).

Needless to say the best "flat earth" land survey program ever is LanDesign from the same author of LandMark while the best, most powerful and easiest to use DTM software is HighRoad from Creative Engineering in Australia. NNA should really take a close look to both as future add-modules for LandMark.

HighRoad has both manual and automated feature strings built into that works great with surveying feature coding saving drawing time.

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Eric the most simple way to input the collected land survey 3D point data (ID, Y, X , Z, Description or code) is a Comma Spaced Values format (CSV) since it allow the user to review, edit and modify these values easily in MS EXCEL worksheet prior to importing them into VW09 and generate the DTM (LandMark).
This is exactly what Import Survey Data allows, except it has a bug that prevents inclusion of alpha numeric data in the ID field. This data ends up in stake objects, which also has a bug as if the stake mode is set to "display as 2D graphic only", the elevation shows incorrectly and get3dcntr Vectorscript function returns incorrect results.

Would someone mind posting a link or list of set of standard codes used by land surveyors.

Edited by IanH

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Thanks. Also very interesting. Make my life easy - as a garden designer I just code all my points as GRDN ;)

For my TS (Leica TCR705XS using Leica Geo Office), unfortunately I cannot seem to get point codes exported on the same line as the point measurement, so I will either have to write my own import, or initially, just stick with prefixing the point ID and not making use of the suffix - string gets too long to be useful and my needs are much simpler.

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