PLANNED VS. REAL CITY

Transcription

1 LANNED VS. REAL CITY 3D GIS for Analyzing the Transformation of Urban Morphology ilar Garcia-Almirall, Francesc Valls Dalmau, Montserrat Moix Bergada {pilar.garcia-almirall, francesc.valls, upc.edu 17th AGILE Conference on Geographic Information Science 4th June 2014, Castellón (Spain)

2 INTRODUCTION Cities are constantly evolving: buildings are built and demolished, altering the landscape of our cities. Urban lans describe what we want our cities to be, undergoing revisions as we change our vision of the future of our cities. This paper presents a methodology to model the interactions between what the city is and what it wants to become. Source: Registre de planejament urbanístic de Catalunya

3 CASE OF STUDY The city planners wanted to know with precision the compliance of the buildings with the maximum heights allowed by the planning regulations. The case of study was the old quarter of the Sant Andreu District in Barcelona, around its main commercial street, Gran de Sant Andreu. It included the centre of the former town, and the development it underwent in the 19th century when it was incorporated into Barcelona. This historic development resulted in a complex urban structure suitable to use as workbench to test our methodology. Source: Institut Cartogràfic i Geològic de Catalunya

4 DECODING HEIGHT INFORMATION The height of buildings was stored as 2.5D cartography, where the height attribute of each polygon was a string that encoded several pieces of information, including the number of floors below and above street level. However, ventilation courtyards and staircase towers did not have a height attribute but a code that identified them as such ( and ESC ). A methodology had to be developed to automatically assign height values to these types of entities from their spatial context (the height and parcel information of neighbouring sub-parcels). ESC I ESC IV I I I I -I+VI V +I ESC I -I+V VI VI I I I ESC ESC Source: Dirección General del Catastro

5 VENTILATION COURTYARDS Ventilation courtyards allow placing uses like kitchens and bedrooms in the core of the building and still be able to get ventilation and natural light. These courtyards are geometrically voids, but from the planning regulations point of view they should be considered built up. For sub-parcels representing ventilation courtyards, the assigned value was: a) The lowest height of its adjacent subparcels b) Considering only the neighbours belonging to the same parcel

6 STAIRCASE TOWERS Staircase towers are as high as the top floor they serve in their parcel because they have to provide access to it. According to planning regulations, the volume that protrudes and give access to the roofs should not be considered as overbuilt. For sub-parcels representing staircase towers, the assigned value was: a) The maximum height of its adjacent subparcels b) Considering only the neighbours belonging to the same parcel

7 NEIGHBOURING VOLUMES HEIGHT TABLE Since the GIS used was non-topological, a methodology had to be implemented using SQL: A dictionary of key-value pairs was made to translate the alphanumeric encoding to a numeric value measuring the number of floors above street level. volumes poly_id parcel_id hcode volumes_height poly_id type_dictionary hcode height type volumes_height poly_id volumes_height poly_id parcel_id height type lines_volumes line_id A tool to convert polygons to lines was used to get an adjacency table with 3 ID fields: line ID, left polygon ID and right polygon ID. A table with the attributes of the polygons on both sides of each line was built from the tables described previously. parcel_id type lines line_id poly_id_l poly_id_r parcel_id type poly_l parcel_l height_l type_l poly_r parcel_r height_r type_r

8 STAIRCASE TOWERS HEIGHTS lines_volumes line_id poly_l parcel_l height_l type_l poly_r UNION QUERY SUBSET type_r = "E" parcel_l = parcel_r SUBSET AGGREGATION stair_id max(height) Diagram of the process to reshape the adjacency table to get the height of staircase tower volumes. The result is a table with the polygons marked as staircase towers with their corresponding height. parcel_r height_r type_l = "E" parcel_l = parcel_r type_r

9 VENTILATION COURTYARDS HEIGHTS lines_volumes line_id UNION QUERY Diagram of the process to reshape the adjacency table to get the height of ventilation courtyard volumes. poly_l parcel_l height_l type_l poly_r SUBSET type_r = "" hcode_l <> "E" parcel_l = parcel_r SUBSET AGGREGATION vent_id min(height) The result is a table with the polygons marked as ventilation courtyards with their corresponding height. parcel_r height_r type_l = " hcode_l <> "E" parcel_l = parcel_r type_r

10 OVERLAY OERATIONS The corrected heights were compared to the height the plan allowed using two mutually exclusive spatial operations: A spatial intersection, the result of which was the fragments of sub-parcel inside zones. A spatial difference, the result of which was the fragments of sub-parcel inside systems (roads and parks). With the result of the overlay operations it was possible to determine the conformity to the urban plan for each of the fragments from their building height (HB) and planned height (H). Fragment lan entity Condition Operation Symbology Underbuilt Zones HB - H < 0 Intersection Blue hues Conformant Zones HB = H Intersection Grey Overbuilt Zones HB - H > 0 Intersection ink hues Overbuilt Systems HB > 0 Difference Dark green Conformant Systems HB = 0 Difference Light green Spatial intersection Spatial difference

11 FRAGMENTS FROM OVERLAY OERATIONS Resulting fragments from the two overlay operations

12 ARCEL LEVEL AGGREGATION It is not legally allowed to compensate overbuilt volumes with underbuilt ones inside a parcel. Aggregate calculations had to be performed separately for both situations to avoid the aggregate operations adding positive and negative numbers. That would be mathematically correct but not possible according to the regulations. RRRRRRRR BBBBBBBBBB AAAAAAAA = HHHH SSSSSSSS AA SSSSSSSS SSSSSSSS AAAAAAAAAAAAAA BBBBBBBBBB AAAAAAAA = HHHH FFFFFFFFFF AA FFFFFFFFFF FFFFFFFFFF OOOOOOOOOOOOOOOOOO = HHHH FFFFFFFFFF HHHH FFFFFFFFFF AA FFFFFFFFFF FFFFFFFFFF UUUUUUUUUUUUUUUUUUUU = HHHH FFFFFFFFFF HHHH FFFFFFFFFF AA FFFFFFFFFF FFFFFFFFFF OOOOOOOOOOOOOOOOOO iiii SSSSSSSSSSSSSS = HHHH FFFFFFFFFF AA FFFFFFFFFF FFFFFFFFFF

13 TOTAL OVERBUILT AND UNDERBUILT AREA Overbuilt area per parcel Underbuilt area per parcel

14 3D VS. 2D RERESENTATION The representation of the results using 2D maps was unable to convey the complex volumetric information successfully because height data had to be abstracted to be represented in plan view as colour scales, hatch densities or labels. The use of 3D imagery allowed the authors to represent the volumes in a more natural and intuitive way since it matched the way we experience our cities. The third dimension allowed the authors to display overlapping information without having to resort to 2D representation constructs such as transparency or hatching. Underbuilt Real Allowed Real Allowed Real Overbuilt Allowed Underbuilt fragment Compliant fragment Overbuilt fragment

15 OVERBUILT AND UNDERBUILT FRAGMENTS

16 REALITY AND 3D RERESENTATION Source: Bing Maps

17 CONCLUSIONS AND FUTURE WORK A methodology to study adjacency relations in a non-topological GIS was developed using SQL, which allowed assigning height values to entities that didn t have this attribute from their spatial context; this methodology is being developed to be able to be applied in other applications. The 3D visualization techniques allow the discovery of patterns not obvious even for trained professionals and is a valuable tool to communicate the results of the analysis. To improve the accuracy and usefulness of the visualization of the results it is proposed: The incorporation of a Digital Elevation Model (DEM) in the 3D model. The use of Augmented Reality tools to visualize the results on site.

18 Thank you!