26 th International Cartographic Conference August 25 – 30, 2013 Dresden, Germany 3D MAPS SCALE, ACCURACY, LEVEL OF DETAIL Prof. Dr. Temenoujka BANDROVA University of Architecture, Civil Engineering and Geodesy, Eng. Stefan BONCHEV Sofia, Bulgaria
Content Introduction Questionnaire Answers Scale Accuracy Level of Detail Conclusion
Introduction In the traditional 2D mapping the elements such as scale and accuracy have clear definition. What about 3D maps? What does large-scale 3D map mean and what does small-scale 3D map mean? Purpose: Describing and analyzing the terms scale, accuracy and level of detail (LoD) in 3D mapping. Provoking a discussion
Questionnaire Participants: Cartographers Geodesists Geographers Computer graphics scientists Students
Questionnaire 9 questions divided into 3 groups: Scale Accuracy Level of Detail Most of the questions contain multiple choices of answers The answers were collected online 15 participants
Scale The term “Scale” in 3D maps has more complicated understanding than in 2D maps... The first question: 2D maps could be large-, medium- or small-scale ones. In your opinion, could we have the same typology (i.e. large, medium and small-scale) in the case of 3D maps?
Scale 1. 2D maps could be large-, medium- or small-scale ones. In your opinion, could we have the same typology (i.e. large, medium and small-scale) in case of 3D maps? Responses % Count Yes, Depending on area of visualized territory 46.7 7 Yes, Depending on zooming 40.0 6 Yes, Depending on LoD 40.0 6 Yes, Depending on data source 13.3 2 No 0.0 0
Scale
Scale Comments: • The usage of maps is mostly based on density of content . • Yes, because there is a horizontal scale and a vertical scale. Likewise objects are usually modeled in real size using relevant software.
Scale 2. In your opinion, which scales of data source are most appropriate for creation of 3D map? for small-scale Rating 3D for large-scale for medium-scale 3D map 3D map map Count 1:1 87.5% (7) 37.5% (3) 50.0% (4) 8 1: 500 / 1: 1000 85.7% (12) 35.7% (5) 28.6% (4) 14 1: 10 000 18.2% (2) 90.9% (10) 9.1% (1) 11 1: 25 000 8.3% (1) 83.3% (10) 25.0% (3) 12 1: 50 000 11.1% (1) 33.3% (3) 66.7% (6) 9 1: 100 000 and larger 10.0% (1) 0.0% (0) 90.0% (9) 10
Scale
Scale Comments: • Depends on purpose and area presented on 3D map (city, skiing resort, mountain range, province...) • Because objects are modeled in real size and then users can use their desired scale. (About the answer 1:1)
Scale 3. According to its scale, what kind of elements should be visualized in a 3D map? for small-scale Rating for large-scale for medium-scale 3D map 3D map 3D map Count Terrain; Surface 86.7% (13) 93.3% (14) 80.0% (12) 15 Rivers, hydrographic objects (lakes, dams, etc.) 80.0% (12) 100.0% (15) 86.7% (13) 15 Buildings 86.7% (13) 60.0% (9) 40.0% (6) 15 Roads and railways 80.0% (12) 93.3% (14) 80.0% (12) 15 Textured facades 92.3% (12) 23.1% (3) 15.4% (2) 13 Symbol system for small objects 60.0% (9) 53.3% (8) 46.7% (7) 15 Plants 86.7% (13) 26.7% (4) 13.3% (2) 15
Scale
Scale Comments: • Build-up areas in small-scale 3D map
Scale 4. Do you agree with the term “3D map at a scale of 1:1”? Responses Count % No, because it is not possible 60.0 9 Yes 40.0 6
Scale If yes, what is the expected smallest lowest level of details on the map... (Comment): • Buildings and plants • LoD 3 • Yes, only in model space in relevant software
Accuracy 5. In 2D maps it is possible to calculate the accuracy of the map if its scale is known. In your opinion, is it possible to calculate the accuracy of a 3D map if we know the scale and the accuracy of data sources? Responses Count % The accuracy could be different on XY and Z (H) coordinates values 53.3 8 Yes 40.0 6 No 6.7 1
Accuracy 6. In your opinion, which factors impact the accuracy of 3D maps? Responses Count % Data sources 86.7 13 Data processing 60.0 9 Technology of 3D map creation 53.3 8 LoD 53.3 8 Software 33.3 5
Accuracy
Accuracy Comments: • Generalization always plays a crucial role in map accuracy • Different LoDs have different accuracy (e.g. LoD 1,2 and 3 accuracy is defined by totally different parameters than LoD 5 and 6 and should be defined separately)
Level of Detail 7. We propose 6 levels of detail to be included in a 3D map. Please, select the LoDs that should be included on a 3D medium-scale map? You are invited to share your comments in the textbox below the question. Responses Count % LoD1 (terrain and terrain objects, hydrograph) 84.6 11 LoD2 (infrastructure) 76.9 10 LoD3 (extruded buildings) 76.9 10 LoD4 (building’s roofs) 30.8 4 LoD5 (3D architectural elements and/or photorealistic textures) 15.4 2 LoD6 (3D symbol system) 46.2 6
Level of Detail
Level of Detail 8. Do you think that LoD1 (terrain, terrain objects, hydrology) should be divided into more LoDs? Responses Count % Yes 53.85 7 No 46.15 6
Level of Detail Comments: • Yes, either predefined or computer on the fly. Look at Google Earth: zooming in and out changes the LOD of the terrain • Yes, I think so • Yes, according to distance from view point • Yes. Especially for 3D large-scale maps • Yes, depending on the scale which is used • Yes. In two maybe
Level of Detail 9. In CityGML LoD cannot exist without previous one (You cannot create LoD4 if you didn’t complete LoD3). Do you think that in 3D map LoDs can exist independently one from another (for example LoD1, LoD3, LoD6)? Yes 11 No 2
Level of Detail Comments: • Yes. Your LODs span different themes whereas CityGML LODs span different representations of the same object. Note that you run into the same problem with your LOD 3 and 4; you cannot have LOD4 without LOD3 (or you'll have floating roofs) • Yes, sure. If the objects can be created independently at different scales • Yes, they can • Yes, but limited: LoD1 is always crutial, espetially LoD6 is quite independed from the others • Yes. Too many LoDs can harm the readability of a 3D map • Yes. They should be able to exist independently, so depending on the application of the map some can be excluded. for example LoD1 for large scale maps. Or in some maps LoD6 might be significant while LoD 5 is not needed and can be replaced by photo-texturing (e.g. touristic maps) • If we use a single constant LoD as basis for all exports it could be possible • Yes, but then this is a hybrid 3D map • No. There is need from hierarchy
Conclusion The questionnaire survey should continue in 2 directions: • More participants should be included • Another way of survey: practical achievements, users’ requirements, technology developments. Small-scale 3D Large-scale 3D Medium-scale map Elements, contain in 3D map map 3D map Terrain; Surface ++ ++ ++ Rivers, hydrographic objects (lakes, dams, etc.) ++ ++ ++ Buildings ++ + ? Roads and railways ++ ++ ++ Textured facades ++ - - Symbol system for small objects + + + Plants ++ - - If you like to participate in this survey, please go in: http://www.surveymonkey.com/s/H3R77GP
INVITATION 5 th International Conference on Cartography and GIS & Seminar with EU cooperation on Early Warning and Disaster Management 15.-21. 06. 2014 Riviera, Varna, BULGARIA
Topics Conference Cartography Concepts in BigData Environment GIS Technologies and Related Disciplines Web Cartography and Digital Atlases Map Design and Production Cartographic Visualization Volunteer Geographic Information Virtual Geographic Environment Cartography and GIS in Education; GPS Technologies Contemporary problems using geodetic coordinate systems and map projections Geospatial data acquisition by remote sensing technologies for cartographic purposes GIS for Geology and Natural Sciences Seminar with EU Cooperation on Early Warning & Disaster / Crisis Management European Concepts for CM and EW Visualization of Geodata and Geoinformation in CM and EW User Needs and Context Mapping From Discovery to Full Interoperability in CM and EW SDI and CM: INSPIRE Influence "Speaking the Same Language - Semantic Aspects of CM" Sensor Mapping for EW and CM
Publications The best papers will be proposed for publication in a Book titled: Thematic Cartography for Society Publisher: Springer Book topics: User-friendly Internet Cartography User-oriented Map Design and Production Context-oriented Cartographic Visualization Map interfaces for Volunteered Geographic Information Sensing Technologies and their integration with Maps Cartography in Education On-line publication CD Publication, ISSN Abstract/ paper submission Deadline: 10. January 2014
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