Massachusetts Institute of Technology - Department of Urban Studies and Planning 11.520: A Workshop on Geographic Information Systems 11.188: Urban Planning and Social Science Laboratory Lecture 15: Terrain Models, Cartograms, 3D & Course Wrapup Joseph Ferreira, Jr. Administrative • Project writeup due today (and must be handed in by Friday to avoid penalty) o see Project page for details • Course evaluations: extra copies are available today if you didn't already turn one in at the Monday project presentations Test comments • Test solutions are now online on the Test page. We were pleased with your generally good performance on the test. Take a look at the solutions to clarify your reasoning about the maps and other answers. Here are some specific comments o Everyone missed one subtle aspect of mapping town density. The map shows 351 towns but has 600+ polygons in the matown00 theme due to islands, rivers, and other features that split towns into multiple parts. The quantile classification must be done on the 351 towns, not the 600+ polygons. Hence, the breakpoints for the 20/40/60/80 percentiles should be determined by sorting the density column in the madoreqv table before joining to the map. o Many of you identified a grid cell in Williamstown as the part of the state that is furthest from major highway exits. However, the southeast part of Nantucket is a 51 km from an exit (3 km further). You received partial credit for the correct distance to the corner of Williamstown.Terrain Modeling and 3-Dimensional Visualization • Representing height (Z) o Contour lines (each line is the locus of points at a constant elevation) o Surface models (2.5D)  DEM - digital elevation models (e.g., matrix of 30m elevations)  TIN - triangulated irregular network  approximate a smooth surface using interconnected triangles  quick visualization by shading triangles based on slope and aspect  Building a TIN from contour lines  Computing slope and aspect o 3D models  Add Z to points, lines, polygons  Add surfaces and volumes as objects defined by a collection of planar polygons  Recognize difference between extruding 2-D shapes and allowing sloped roofs with overhang  Solid modeling  describe objects such as cylinders and spheres by continuous math functions  use computational geometry to handle intersections, differencing, etc. • ArcScene for 3D visualization o Example using a TIN for Boston  M:\data\bostin\hpy_bos_t contains the TIN model  TIN was developed using ArcGIS from elevation (hypsography) data from USGS  Use ArcScene to view 3D data  Add 3D-Analyst extension for additional capabilities o Surface analyses for: contour lines, slope and aspect estimates, hillshading o Using slope/aspect or hillshading for visualization and analysis  Darken as if lighted from northeast corner  Find all the south-facing roads o Draping layers on top of TIN: base heights, z-exaggeration, offset.Course Wrapup • Review progression of topics/labs during semester • Highlight other tools/issues that we haven't had time to cover o Entering and Editing geometry o Handling one-to-many and many-to-many relationships o Additional analysis tools: geostatistics, network analysis, etc. o Interoperable geospatial services • Other classes o 11.521 (11.523/524) - spatial database management and advanced GIS project o 11.522 - research seminar on urban information systems o 11.220 - Quantitative Reasoning and Statistical Methods for Planning o IAP activities - GIS minicourses taught by Dan Sheehan (IS&T) and Lisa Sweeney (Libraries) o Harvard: GSD and Engineering classes o BU: remote sensing classes Last modified 14 December