An improved LOD specification for 3D building models

Abstract

The level of detail (LOD) concept of the OGC standard CityGML 2.0 is intended to differentiate multi-scale representations of semantic 3D city models. The concept is in practice principally used to indicate the geometric detail of a model, primarily of buildings. Despite the popularity and the general acceptance of this categorisation, we argue in this paper that from a geometric point of view the five LODs are insufficient and that their specification is ambiguous.We solve these shortcomings with a better definition of LODs and their refinement. Hereby we present a refined set of 16 LODs focused on the grade of the exterior geometry of buildings, which provide a stricter specification and allow less modelling freedom. This series is a result of an exhaustive research into currently available 3D city models, production workflows, and capabilities of acquisition techniques. Our specification also includes two hybrid models that reflect common acquisition practices. The new LODs are in line with the LODs of CityGML 2.0, and are intended to supplement, rather than replace the geometric part of the current specification. While in our paper we focus on the geometric aspect of the models, our specification is compatible with different levels of semantic granularity. Furthermore, the improved LODs can be considered format-agnostic.Among other benefits, the refined specification could be useful for companies for a better definition of their product portfolios, and for researchers to specify data requirements when presenting use cases of 3D city models. We support our refined LODs with experiments, proving their uniqueness by showing that each yields a different result in a 3D spatial operation.Keywords: Level of detail; 3D city modelling; 3D GIS; 3D building models; CityGML; Scale Highlights• CityGML LODs are an industry standard for conveying the grade of 3D city models.• The 5 LODs are not defined precisely, and they are not sufficient for this purpose.• We present a refined series of 16 LODs that overcomes these issues.

The effect of acquisition error and level of detail on the accuracy of spatial analyses

“…a bounding box) and the vertices would not correspond across multiple LODs (Arroyo Ohori, . In 3D GIS, LOD1 and LOD2 are usually realized using the same footprints (Biljecki et al, 2016b), hence this does not affect much of our work and while we do not contend that we have a solution here, it is certainly important to acknowledge the occasionally blurry distinction between representation and acquisition errors.…”

“…The standard defines LODs that progress in geometric detail and semantic information: LOD1 is a block model, LOD2 is a generalized model containing basic roof shapes, and LOD3 is an architecturally detailed model containing openings and facade detail (Kolbe, Gröger, & Plümer, 2005). These LODs roughly reflect the different outcomes of different acquisition techniques (Biljecki, Ledoux, & Stoter, 2016b). For instance, LOD1 is usually produced by extruding footprints (Ledoux & Meijers, 2011), LOD2 can be acquired automatically from lidar data (Kada & McKinley, 2009), while LOD3 usually involves substantial manual work or is obtained after conversion from architectural sources (Donkers, Ledoux, Zhao, & Stoter, 2016).…”

Automation of Building Permission by Integration of BIM and Geospatial Data

“…An alternative to including a BIM model with the building permission process would be to include a CityGML LOD3 model. To ensure that such an LOD3 model contains sufficient details for the rule checking it must be defined how to design the model since the LOD levels in CityGML are somewhat ambiguous [52]. More technical building regulations must still be checked against a BIM model but that could be performed with proprietary model checking tools such as Solibri Model Checker (Solibri Inc., Helsinki, Finland) in a separate process before the building is checked against regulations in the detailed development plan.…”

Proposal for a New Lod and Multi-Representation Concept for Citygml

“…The concept is implemented as an Application Domain Extension (ADE) for CityGML. In a subsequent research, Biljecki et al (2016a) refine the specification into a larger number of LoDs from the geometric point of view to mitigate multiple valid variants of CityGML LoDs (e.g. two geometric instances of LoD2: one with and another one without the roof superstructures modelled).…”

“…Hence, a number of new approaches entered the discussion. They range from more practice-oriented (Nagel 2014), to very detailed Löwner et al, 2013) or even go beyond the context of CityGML (Biljecki et al, 2013;Biljecki et al, 2014;Biljecki et al, 2016a). However, after (rf.…”