Do you remember the first time you were shown GIS
technology? The smile which that introduction most certainly brought to
your face may have faded over time, but I hope you are continually
stimulated by the thought of new ways you can use the technology. For
me, the use of 3D in GIS is like my first cup of coffee in the morning.
After 30 years with GIS, the smile still comes to my face, not from
traditional 2D work but from things we now do in 3D. Since I suspect
that most readers of this editorial have never created a 3D GIS
environment, it is my belief that GIS users have simply not thought
about the available opportunities using existing 3D technology. GIS
users are so entrenched in their 2D world that they dont even know how
to get started in 3D. With this editorial, I hope to stimulate you to
expand your horizons and look at 3D, using currently available tools
and data formats. Have you ever heard of the multipatch? If you think
that 3D buildings and other landscape features cannot be treated as GIS
layers, please read on.
To illustrate my point, let me describe three different ways someone
might create a 3D GIS environment. All three will start with a terrain
model and have an orthophoto or land cover layer draped over the
terrain. The next step would be to begin populating this environment
with 3D landscape features (e.g. buildings, trees, signs, etc.). Using
a software package like SketchUp Pro, I can construct a building that I
want to add to the landscape. How I use this building model in my 3D
GIS scene is critical to the scenes effectiveness and utility. My
first option is to treat the building as a graphic that I can simply
add to the scene and position wherever I desire. Needless to say, this
is not what I think of doing when I work in GIS. The graphic is as dumb
as a bag of rocks. It has no attributes and no spatial coordinates that
would allow it to work with other features or layers.
My second option is to use this building as a symbol in my 3D scene. If
you are an ESRI user, this is the easily accessible option in the
ArcScene and ArcGlobe environments. In these ESRI 3D viewing
environments, building symbols are associated with a point layer. The
last time I looked at my house, it was not a point. It is an object
that has a footprint, with area (and volume). The building symbol does
not store attributes or know its spatial location. It must rely on its
associated point feature for attribute and coordinate information.
Symbols may work for the 2D environment, but not in 3D.
The use of graphics or symbols is not what I want or need in my 3D GIS.
I want buildings to be GIS features. They should have attributes, know
their spatial location in X, Y and Z space and be able to participate
in GIS analysis. Judging by the very limited acceptance of 3D GIS using
symbols or graphic representations, it would seem that most GIS users
share my feelings. To make the investment of time and effort, we need
buildings to be smart participants in GIS activities. If you are an
ESRI user, this capability has been available to you since 1998. The
multipatch is a type of shapefile designed to accommodate the 3D
geometry of a building or other landscape feature. Look at page 20 of
document and you will find the multipatch shapefile specifications.
Space does not permit a greater explanation and to be honest, none is
needed. The multipatch uses triangle strips and fans and might best be
thought of as the origami of the 3D GIS environment.
Now, if the building I have created in SketchUp is saved to a
multipatch format it becomes a GIS feature. My multipatch building can
be added to a buildings feature class, be assigned attributes and begin
to participate in geoprocessing tasks. Within my understanding, the
multipatch is the only format that allows 3D objects to participate as
GIS features. If there are others, please share them with all of us.
Using the multipatch is the third way to add buildings to the 3D
landscape. Why would someone want to present a building as a graphic or
a symbol in a 3D GIS? Is it any wonder why 3D has not caught on? If we
are going to do 3D, lets do it right. Just imagine for a minute that
the building we created could be an individual GIS feature class and
the rooms or the floors of the building could be recognized as the
individual features. This would mean that I could have the ability to
show the location of all commercial office space in a 3D environment. I
could develop the ability to track fire fighters in a burning building.
Just think about the opportunities and see if the smile mentioned
earlier does not return to your face.
So why has the use of multipatch not taken off? It is a part of the
ESRI shapefile specifications and allows objects like buildings to be
treated as GIS features. The reason, I am going to speculate, stems
from the intense loyalty of the ESRI customer base. Since there are no
tools in any of the ESRI software to make multipatch buildings, users
must look to a third-party for a solution. This is something ESRI users
seem very reluctant to do. Proof for my hypothesis comes by asking
anyone to identify a third-party-developed extension to ArcGIS that has
been very successful and does not have ESRI on the box. In the case
of the multipatch, the only affordable option to create 3D GIS features
comes through the use of SketchUp Pro. Before being acquired by Google,
the developers of SketchUp (@Last Software) created a free plug-in that
allows users to save their work to multipatch. Has the ESRI loyalty
blinded users to the opportunity to transition to 3D GIS and start
using the multipatch? It would seem so. In my professional work, we
have been using the SketchUp solution for several years. The creation
of this free conversion capability has made 3D GIS work possible. The
folks that created the original plug-in are still working on SketchUp
Pro (Version 6 is coming soon) and want to see this link to ArcGIS and
the multipatch continue.
Last week I had a booth at the local high school career fair. This was
the fifth year in a row that I have participated in this event. This is
my contribution to GIS Day. The first few years were really slow. 2D
really did not go over very well. Last year, interest took a great leap
forward, partially because I had built the school in 3D and I could
also show the new Google Earth. This year was by far the busiest I have
experienced. Students and teachers were talking about Google Earth and
a number of students had found the free Google SketchUp. I had several
inquiries about possible internships. On my laptop I had the local
imagery used in Google Earth and I was running ESRIs 3D Analyst to
bring the conversation back to GIS and its powers of spatial analysis.
These young people get it. What is it going to take for the rest of us
to see what they see and have come to expect?
As a way of measuring the user knowledge of the multipatch, the staff
of Directions Magazine has created a user poll that needs your
input. Please make sure to offer your input. As always, your comments
to this editorial are very much desired.