CityGML

  1. The CityGML encoding standard is a rich and valuable road map for building 3D urban geo-databases – kudos to all involved.
  2. LiDAR and laser scanning are the most appropriate technology for building out these databases.
  3. We can choose to take advantage of this or re-invent the wheel.

citygml

In preparing for my presentation for the 3D Fusion Summit I have had a chance to look a lot more closely at the CityGML standard. First of all, since I know first hand how difficult it is to produce something like this, I want to recognize the work of all involved, including the 3DIM Working Group, the OGC and the Special Interest Group 3D of the Initiative Geodata Infrastructure North-Rhine Westphalia. The latter is a group in Germany that is actually responsible for delivering the standard, and who, along with other groups in Germany, have been the leaders of this effort worldwide.

In addition, the 3DIM working group includes Autodesk, Bentley and the Ordnance Survey to name a few other groups. Bottom line – a number of major players are involved with this effort on a worldwide basis. Time to pay attention.

I think it is also important to note that CityGML is described as an encoding standard. If you take the time to read this document you will realize that this is a perfect description. The standard lays out the details of an XML schema for representing most of the elements of an urban landscape including buildings, city furniture, vegetation, water bodies, etc. If the industry buys in, there can be an elegant exchange of information among all stakeholders.

CityGML also specifies 5 levels of detail (LOD), another important data model organizational concept. These range from a 2.5 D digital terrain model to specifying doors and windows. The standard includes  a table of dimensional accuracy associated with each LOD. It is noted that this is just preliminary and that more work needs to be done in this area. I agree.

LiDAR and laser scanning have the potential to be the catalyst for a 5 to 10 year effort to build out these 3D CityGML geo-databases. This is the only realistic approach to acquiring this data in a cost effective manner.

CityGML provides the road map. GIS never had this. We don’t have to reinvent the wheel, unless we want to.

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9 Responses to CityGML

  1. Ed Oliveras says:

    Gene,
    What purpose does the digital city info serve?
    Who wants 3d models of the city and what do they do with these models?

    • Gene V. Roe says:

      Well, that is an interesting question. There is a worldwide interest in building 3D city models. One of the main issues is with the LOD – level of detail. This is where the real the answers to your questions have to be framed. If it is only for visualization purposes than scanning is not likely to make sense or be cost effective, but if the application requires higher dimensional and locational accuracy in 3D then at some point laser scanning and LiDAR are going to make sense.

      The potential applications include:

      Urban Planning
      Permitting
      Assessing
      Solar rights
      Shadow Studies
      Tourism
      Emergency planning
      Homeland Security

      I think you get the idea. It’s all made more understandable with a 3D model.

      • Laurence McKinley says:

        Hi Ed, I might have some answers that might be helpful to you. Our company has been creating 3D buildings from airborne LiDAR for municipalities here in Germany since 2007 using software we developed ourselves, BuildingReconstruction.

        I think the visualization and analysis aspect is clear: you can load 3D models of a city into ESRI to perform analysis, or convert the buildings to KML/Collada for quick and easy distribution both inside and outside the organization. In our experience, the visualization has been used for urban planning/renewal, viewshed analysis and city marketing/tourism. Our customer the city of Dresden even shared their 3D city model with Secret Service to establish security zones beforePresident Obama visited the city two years ago.

        If you needto capture specific information about a building, then a LiDAR scan made from the ground or from the air is useful. Examples here would be ridge height, building azimuth, building volume, etc.

  2. Sivan says:

    Please give the survey company of this 3d city modeling using Lidar project
    sivanmtech@gmail.com is my add

  3. Mariano says:

    Could someone tell me what is CityGML? Is it a program or lenguage? How can I used? I have read about it but I can not undestand what it is? Could someone help me? I am going to appreciate your help. Thanks.

    • lidar says:

      It is an OGC standard – http://www.citygml.org/

      • Mariano says:

        Hello Lidar,

        Thank very much for you information. Although, I know that is a Open Geospatial Consortium Standard and I have read that webpage before. But I think it is not a program, isn’t it? Because, It is possible to used it in differents programs like Google skeptchup and others sofware indicated in that web page.

        Another question, Are there any article that show how I can process lidar or laser scanning data in CityGML?

        I apologise for these stupid questions but If I can find answers to them, it will be very helpful.

        • Laurence McKinley says:

          Hi Mario,
          I don’t have an article to send you but rather a few links that illustrate how CityGML is actually implemented: BuildingReconstruction Software

          I don’t know if you are thinking about using terrestrial or airborne LiDAR, but in the latter case we have software for creating 3D buildings with CityGML as an export format: 3D-CityDB

          The subject of processing LiDAR data into CityGML format is too lengthy for me to answer here but feel free to contact me: lmckinley@virtualcitysystems.de

  4. Mariano says:

    Hello Lidar,

    Thank very much for you information. Although, I know that is a Open Geospatial Consortium Standard and I have read that webpage before. But I think it is not a program, isn’t it? Because, It is possible to used it in differents programs like Google skeptchup and others sofware indicated in that web page.

    Another question, Are there any article that show how I can process lidar or laser scanning data in CityGML?

    I apologise for these stupid questions but If I can find answers to them, it will be very helpful.

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