International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 RiskCity Exercise 4: Generating an elements at risk database Cees van Westen (ed)

International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Elements at risk / Assets What may be impacted by a hazard event?

International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Two options When you don’t have any available data: We assume that you have at least a high resolution image from Google Earth When you have available data: Building footprint map Lidar DSM Census data Depending on your interest in the topic you may select to either do Exercise 3.1 (creating a database by starting from scratch), or Exercise 3.2 (creating a database with available footprint information). You can also decide to do both exercises, although that might perhaps take a bit too much time

International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 If you don’t have data You have to: Generate mapping units Create the attribute data for: Urban land use Number of buildings Population

International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Flowchart: do it yourself option High res image Boundaries Landuse Nr Buildings Input data Population Polygonize Screen digitize boundaries Mapping units Interpret land use type Sample # buildings by landuse type Calculate # based on land use type Calculate # based on land use type & building #

International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Downloading imagery from Google Earth Many area in the world are covered by high resolution imagery. Better first consult than download For detailed download you need Google Earth Pro (cost 400 US $) You can download 4000 * 4800 resolution Here we don’t have Google Earth Pro on all computers. Only one in room 4 – 105 We have downloaded it already for you At home you might like to try the trial version of the Goolge Earth Pro, which allows to download high resolution images. Go to:

International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Digitizing maps X Y Scanning (automatic digitizing) Editing Improving Vectorizing Apply attributes X Y Manual digitizing Raster mode Vector mode Sensor Improving Apply attributes Digital Landscape Model

International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Digitizing mapping units Screen digitizing from high resolution image, on the basis of a digital road map Checking segments, and generation of polygons with unique identifiers

International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Digitizing mapping units High res image Digitize segments Added segment Digitize a new point Create a node / remove a node Select points and move them Select lines and rename / delete them

International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Check segments Digitize segmentsCheck segments Added segment Before making polygons you have to make sure all lines are connected Error types: Dead end in segment (1) Intersection without node (2, 3) Double line (4) Self overlap (5)

International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Determining land use Generation of land use legend, with relevant classes for vulnerability assessment, and keeping in mind population difference Interpreting predominant landuse from the high resolution image

International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Landuse classification Urban landuse mapping:

International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Fill in missing parts

International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Estimating number of buildings Methods: 1. Count all buildings in the map…. 2. Sample buildings for landuse types Steps: Calculate building size building_size:=iff(buildings_sampled=0,0,area/ buildings_sampled) Average building size per land use type nr_buildings:=iff(isundef(buildings_sampled),area/avg_building_size, buildings_sampled)

International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Estimating population distribution Link the number of people per building to land use type Daytime_population:=nr_buildings * person_building * daytime