The Problem with 3D GIS

3D GIS is game changing, it can change the way you view your analysis, it can provide insights which you may have overlooked….but there is a little problem which I may had not shared in my deluge of blogs about how great 3D GIS is…..

…Sometimes it can be hard work. What I mean by this, is that it can sometimes need a lot more consideration than standard methods. Let’s look at some of the major culprits when using Esri ArcGIS Pro 1.4 & Desktop 10.5, keeping in mind that there isn’t many (or any) other 3D GIS you can do this kind of work in.

One of the 3D models built of Kendal, UK

Editing

Once you have converted or built your 3D model into a multipatch polygon you may find yourself struggling to edit or adjust your model.

Split

Having built entire cities, one issue that I’ve come across a fair bit is removing parts of multipatch polygons. For example, when adding multiple models, you may find that two features might overlap and need to remove part of one. In a 2D, standard GIS, you would simply turn the editing on and split the offending polygon.

This doesn’t work in a 3D GIS…Think about it, how does the GIS know where all the planes you require breaking lie with a 3D plane? 3D GIS can do some pretty clever assumptions but I am yet to find a way to remove part of a complex multipatch polygon.

True, within ArcGIS Pro 1.4 there are some editing tools for 3D multipatch features but it is early days at the moment. For simple cubes it is quite easy to adjust and manipulate the model a little but you don’t stand a chance if you have a curved edge.

 

Don’t despair, don’t give up on the 3D just yet, as you know, 3D isn’t new and there are many “workarounds”. One of my favourites is using the ArcGIS Pro “Replace Multipatch” tool. If you want to make multiple edits to a model (feature) you can export the multipatch to a collada format or keyhole markup language (kml) format, edit it in Sketchup, Blender, Meshlab or any of your favourite modelling suites and then import it again without affecting the other features in that layer.

 

If you are extruding simple 2D polygons with the intention of creating 3D mulitpatch polygons, it is a good idea to keep the conversion to multipatch until you explicitly need to. This way, you can edit, split and reshape your 2D polygon within normal ArcGIS Desktop without any issues at all and then draw up and extrude when you are 100% sure it all fits and works okay.

 

In my experience, pre-planning and clarity of the end goal means that you can be prepared for these slight niggles in advance.

Using 3D multipatches in ArcGIS Desktop

Overlay analysis 

So, I’ve built out an entire city of 3D buildings, it looks amazing, last thing to do is clip them by the city boundary….oh, I forgot, the 2D polygon doesn’t truly intersect the multipatch polygon in 3D space, the “clip” tool doesn’t work, the “intersect tool” nor the “merge” tool…in fact you can ignore using modelbuilder.

Clip features

I learned the hard way that 3D features work best with 3D features. Unless the boundary polygon is a 3D feature, then you won’t be able to use spatial analysis to use any kind of overlay querying.

But, there is always a way to trick the system…

Although the multipatch polygon feature is a 3D object, you can still open it in ArcGIS Desktop, meaning that you can use the good ol’ fashioned “select by location” tool. No, it shouldn’t work but it does, furthermore, you can then export your selected data to a new multipatch feature. It begs the question why you can do this and not the “clip” as, in geoprocessing terms, they are the same thing (the clip tool is just the separate bits combined into a single script).

Let’s not get too hung up on it, as it works,

Volumetric Analysis

If you thought that the  “volume” tool was just put there to look clever, think again. It can be a great tool for easily representing floor space or calculating the tonnage of aggregate that needs extracting from the ground to lay a new pipeline.

There is a slight problem though…it can be a little hit and miss, especially when using sourced models.

Calculating Volume

Try adding a model you built in Sketchup, Blender or Meshlab to ArcGIS Pro and then calculate volume (using the add z information tool), Nothing, right? But why? The reason is that it doesn’t like “open” multipatch 3D features, it isn’t fully enclosed. Even if there is a slither of a gap in the polygon and it isn’t 100% enclosed, the tool cannot calculate the volume.

There are other methods whereby you can use a raster surface, like the “surface volume” tool but this isn’t quite as accurate as using your super detailed vector multipatch.

You could try the “Enclose Multipatch” tool, as this closes the multipatch and then running the volume tool BUT you need to consider that unless the multipatch is cut to the surface, for example, where a building sits on a hill and the base isn’t perfectly flat, the volume will not be ideal. So please consider using the data as a high resolution TIN which is merged with the terrain to provide a more accurate volume result.

Oh, last point on this – make sure you use a projected coordinate system that uses metric for your data, a geographic coordinate system will leave you with your volume in degrees….is that even possible?!

Which brings me nicely to –

Issues occur when you don’t specify the datum

Vertical referencing

I distinctly remember my first adventures into 3D through Google Earth, trying to create some of Romsey, UK as 3D buildings using Sketchup. The first hurdle was always figuring out whether the building was “Absolute height”, “On the Ground” or “Relative to the ground”…I mean, what does that mean anyway? I just drew it to sit on the floor, why does it need to ask me more questions about it?

Correct Height Placement

Right now, if you are a regular reader of xyHt or a 3D Geoninja, you will be calling me a muppet. In reality though, you wouldn’t believe how often I am asked about this, especially now that Digital Surface Models (DSMs), Digital Terrain Models (DTMs), bathymetry and other elevation data are so readily available.

Elevation is never easy, worst still, there are either too many or too few options. With the Esri ArcGIS Pro, I am 100% confident that I know where my data sits within 3D space but it is only because I’ve worked with this day in and day out and understand the limitations and data sources.

Let’s consider the Esri “scene” – it’s a cool 3D map and as you zoom into that lovely globe you can see lovely mountains and valleys all popping out of the surface, my question to you is, what elevation data is it using? what is the resolution of that data? You see, I love that Esri provide a detailed and complete coverage elevation surface for the entire globe but the flip side of it is that you cannot know the exact limitations of that surface easily (the information is provided by Esri but it is not a simple “point & click” exercise).

My words of advice here are to use your own terrain when placing 3D multipatch features. Therefore you are in control of both the vertical datum and the resolution of the height.

While I’m here, I want to also point out that there isn’t a “snap to ground” feature in the editing tools within ArcGIS Pro either. This becomes an issue when you bring a model in which isn’t vertically reference, has no vertical datum because you then need to sit it on the surface. Even when your model is a captured point cloud and accurate to 0.5cm, you have no way to accurately place it on the ground. You can adjust it up and down and sit it by sight, though you cannot “snap” it.

The big takeaway here is that firstly, you need to ensure you are confident and know your elevation data if you plan to work in the 3D scene views and secondly that you need to set up your x,y & z coordinate systems correctly from the start to ensure that all the work you do is as precise as possible.

…and yes, I now know the difference between “absolute”, “relative to the ground” & “on the ground”….maybe an interesting blog for another day, though feel free to contact me if you need quicker answers!

And everything else

There are still many things I have not had a chance to mention, for example the complexities of cartographic representation using 3D models in a GIS, or ways of minimising the clashing of overlapping data plus other 3D centric issues such as shadow and light. Maybe a blog for another day?….

Dragons8mycat

 

 

Trying to provide what they don't realise they need

A month into employ with Elliot and the amazing Garsdale Design Team and I am starting to realise the scale of the task ahead….this is the same as almost every other geospatial expert reading this: You could recreate the Earth with enabled 3D and location intelligence but how do you convince people that it is what they need?

For years I’ve read about Business Intelligence Modelling, Smart Cities, Asset Management, Integrated Solutions and all the other really cool phrases doing the rounds at the moment, I’ve been to countless conferences and talks on these super intelligent solutions but when the dust settles and the cold light of day comes, where are the customers to buy it?

Smart City 1

Having sat around the table with some of the top experts in the industry, one thing becomes clear [this is not a sales pitch but to demonstrate a point], Garsdale Design and I can create ANYTHING, cities so smart you have to put your headphones in to block out the breathing…We were playing around and had a small town built in minutes, then using basic GIS we added full attribution which could be reported PER FLOOR of each building and even used as a basis for further analysis. You want the energy efficiency of each building floor? It’s there, you want the building areas blocked by trees, a mere click away….add in demographic data and there is the potential to even find out what type of newspaper each person on each floor reads.

Like I said, there is nothing that we cannot create given a little time – so why isn’t it mainstream? Surely something so cost effective and mainstream would be selling like hotcakes? You would have thought that the UK Government (Listen up Mr Cameron!) would make this mandatory for Governmental bodies to not only collate the data to a single point but to also make the data more efficient. How many times have we heard that we have to wait while Mr X in one department has to talk to Mrs Y in another department because they “don’t deal” with that specific information….Excuse me, but surely in this day and age, shouldn’t all the data be in one place which everyone has access to? Shouldn’t we be analysing ALL the data rather than a jigsaw with missing pieces which only leads to incomplete answers?

3D GIS Intelligence fig 2

Here is where I think that things have been going wrong – We are rubbish promoters of ourselves. Yup, I just said you were rubbish…..

You, like me, didn’t see the bigger picture until it was too late. We sold the world GIS Server systems and cool shiny web maps but we didn’t sell the whole package….we didn’t sell data management. A lot of you (yes I am assigning a little blame) made a quick buck, sold the server and ran….some TRIED to sell some asset management/ data management but weren’t aware that we were going to get 3D GIS and the ability to integrate all the information into a system which could  join the gaps and churn through it all.

And here is the crux of the problem, we now have the ability to provide smart cities and amazingly clever urban modelling but how do we get people to buy into ANOTHER geospatial fad? What will convince them to take another step?

SmartCity2

We (Garsdale Design Ltd) have a plan….but as a collective we need to start providing more intelligent solutions, stop being lazy with the metadata and do more table joining to make the non-geospatial people realise what they are missing.

 

Dragons8mycat

 

Just where are the standards nowadays? (rant)

I am sure I am not the only one, you have the mother of all projects to get some spatial analysis done on by close of business and you go to merge the data for a spot of spatial join action and……there is no consistency, in fact every single data has a different way of structuring its attribute data.

Okay, so maybe you won’t be merging your data together for a spatial join, only a complete noob would be doing that (hello :P) but the point is, where are the standards? You buy survey data and most of its own data uses different attribute labelling formats, you download some Government Open Data and you spend 90% of your time trying to work out what the columns are about…if they are labelled at all!.

This is the modern age, we are looking at big data and cloud based systems yet we can’t even produce 2 data which talk to each other, it is well, embarrassing!! The ironic (or frightening) thing is that I have sat in a few meetings and discussions on Spatial Data Infrastructure (SDI) and each meeting has its own ideas about what needs to be addressed – The hydrographers want something specific to them and then the survey guys want something specific to them….and so on…

Well there are many SDIs about but here’s the problem….too many chiefs and not enough Indians (excuse the analogy), there are too many rules and regulations from too many sources for anyone to make sense of it & without any single specific governing body we end up with everyone having their own ideas over what they think should be right….only most of these guys are analysts, theorists and conspirators, not the people that work with the geospatial data on a day to day basis.

Just a quick scout on Wikipedia reveals just how many different standards are flying around at the moment:

My question to you all is why can’t the field with the object names in be called “Names” or the field with the WGS84 Latitude coordinates (in Decimal Degrees be called “Lat_DD”? Is this too complex?

I’m looking at my Twitter right now and I see 2500 of the best people to answer my question, if not, to spread the word and help to find the BEST answer to the question –

HOW DO WE GO ABOUT GETTING A DEFINITIVE SDI FOR FEATURE ATTRIBUTION?Please feel free to prod me and poke a stick at me if I am completely wrong and there is a standard which should be adhered to, in 10yrs of geospatial work I haven’t found it but I may have been looking in the wrong places. The closest I have got so far is the amazing work being done as part of the Inspire directive, though trying to comprehend it is a real pain and a few of the attribute names are not compliant with shapefile format eg “meanhigherhighwatersprings” & “Gradeseperatedcrossing” is never going to work!

All I want to do is to inter-relate my geospatial data and not spend hours having to rename and re-order the fields so that it I can join 2 tables together! It can’t be that hard….can it?

Nick D