Sources of Geographic Information - GIS Tutorial
Sources of Geographic Information

Geographic Informations Systems are software tools for manipulating spatially referenced information. In order to use GIS, you first must find and understand appropriate GIS data.

Discovering Geographic Data

The great thing about geographically referenced data is that datasets compiled by independent agencies alignes together in a coherent way. Many maps and spatially referenced databases are compiled for administrative purposes. Discovering these resources can be as easy as doing a web search in Google or some such tool. Most cities of any size will have an official web site. Many now have sections of their web sites focused on Geographic Informaion Systems (GIS.) The likelihood of your finding free information about a particular area is usually proportional to the importance of that area to a government agency, and the willingness of that agency to make that information available. Un fortunately many governments around the world like to lock up their informaion so that only favored people can have the advantage of the best information.

Organizations that have a lot of informration to keep track of typically do not use computer aided drafting (CAD) tools to manage their data. Database tools such as GIS are better able to deal with very large datasets and they are deeper in terms of being able to attach meaning to representations. GIS is also more flexible in accomodating real world coordinate systems. Luckily it is not difficult to convert GIS data to CAD formats.

Exploring GIS Data

Lets say you find some GIS data. It is a bunch of files. How do you look at it? This is where you need to start learning about how to use GIS. At the Graduate School of Design, our primary GIS tool is ArcGIS. You can find all of the documentation including some introductory tutorials about GIS in the GSD's GIS Manual Documentation Page. The key to understanding GIS data once you have opened it in a GIS, is to zoom in on details, and to examine the Attributes for the features or cells. For a good tutorial on exploring GIS data and metadata, see Exploring Geographically Referenced Data

General-Purpose GIS Data Resources on the GSD LAN

Every project needs to begin with a study of the overall context. Data such as general shorelines and transportation. The easiest way to begin your gis database is with the collection of data that shops with ArcMap software. For a detailed description of building a contextual database for anywhere, consult the GSD On-Line Manual Page Beginning your GIS Database

ESRI Maps and Data

ArcGIS ships with 6 CDs containing hundreds of layers. These are handy for making maps, but also for general reference. The ESRI Data CDs can be found on the GSD network in L:\public\geo\esridata_9 Click here for a listing of the layers available on these CDs

OpenStreentMap The People's Map

The OpenStreetmap is a project that engages the public in the project of developing digital map data comparable with Google maps. The great thing about this project is that the data are freely available for applications outside of the web browser -- so, for ecample you can download GIS databases of teh openstreetmap data from GeoFabrik Web Site

The Harvard Geospatial Library

We can be proud that our own Harvard Library Digital Initiative has a collection of thousands of geographic datasets and images that can be seartched and downloaded at The Harvard Geospatial Library (HGL). The curators of have recently made available a new tool for exploring their data collections directly through ArcGIS. You can learn more about this from The Harvard Center for Geographic Analysis web site.

Data from National and International Mapping Agencies

As our quest for data becomes more specific, the next most reliable source of data are national and international mapping agencies. Some of these public service agencies are very secretive or charge exhorbitant prices for their data (for example, the British Ordinance Survey and its descendants around the world) which is a shame. But other agencies set a good example, For example:

The US Federal Government has very good information of a level of detail consistent with the 1:25,000 scale USGS Quadrangle maps. YOu can find loads of useful information, including low cost aerial photography of practiaclly any US city, at USGS Seamless Data Viewer. is a new and growing source of information regarding terrain and land cover information, nationwide, and aerial photography for selected areas. and USGS Earth Explorer. For digital terrain information for anyplace in the world, check out the GSD On-line Manual page, Obtaining and Assimilating Digital Elevation Models. This page also covers converting GIS data to CAD formats.

A good Source of data for europe and africa is found at The United Nations Environnment Progarm GIS Data Bank.

Georeferenced Images

A vast amount of information about places can be found in the form of digital images, either scanned maps or digital aerial photographs. Many sources of these are discussed on the The GIS Manual Page on Geographic Images Some of these images may have imbedded georeferencing information that allows it to be aligned with other data in the GIS. If not, then images may be georeferenced using techniques discussed on the Georeferencing Images.

The GSD has Google Earth Pro installed on our lab computers. The pro version accesses the same imagery as the free version but lets you download imagery at much higher resolution (using the File>Save>Image option. Although these images are not georeferenced, a trick for georeferencing these images very precisely is discussed on the page. Georeferencing Images and CAD Data.

Harvard Map Collection

The Harvard Map Collection has hundreds of thousands of maps and atlases. They will help you find maps and these may also be scanned. The Map Collection also has a lot of digital infomration and you can set up an appointment to consult with ther digitla data specialist.

State and Provincial Agencies

The more detailed the information you want, the less likely it is that you will find it for free on the web. At the state level, you may get lucky, and find a site like the Massachusetts GIS These days, even city governments are making their data avaialble on the web. Find the GIS section of the state, city, or county's official web site.

Census Information for the US

Having set up your contextual framework, it will be very helpful to look at your area of interest in terms of demographics and housing. The GSD has the full line of CensusCD products accessible on the network. These make it easy to download census data from 1970 throu 2000, and to map any of thousands of geographical attributes as layers with your other gis data. For instructions on getting your census data, consult the manual page, <="" a="">. If all you need is basic population and housing information, your easiest source would be The ESRI Maps and Data CDs

It is highly reccommended that you read the page Understanding and Mapping Census Data at the GSD before fooling around with census data!

Locations of all Businesses in the US, Downloadable by Zip Code and Business Type

The Harvard Center for Geographic Analysis has licenses for a dataset for market research, ESRI Business Analyst which can be used to extract all sorts of marketing oriented demographics and information about businesses. COntact them to make an appointment to use this.

The GSD has 5 licenses for a spiffy CD business directory that permits you to select from all the businesses in the 2000 yellow pages, and map them in ArcMap. For exhaustive instructions for using this resource at your PC or a public computer, see the on line manual page entitled, Using the Business Directory.

Detailed Data of Local Interest

For local data, it helps to have connections. Studio instructors should cultivate their local connections well in advance of the start of their studio to try to obtain detialed local data. Obtaining local data involves a number of steps. First, you should have a clear idea of the types of layers that are desired(e.g. building footprints, trees, edge of pavement, property parcels, contours, aerial photography, etc.) Then think about what local agencies might have these data. Of course, you would look on the web to see if data are available easily -- or to find contact information of the probable custodians of the data. Then one would write letters or make phone calls. When requesting data you should be very specific about what you would like to find. If you simply ask for GIS data you are likely to get a file of zip code boundaries for the area in question. Of course, you should also ask for metadata!

The GSD GIS specialist does not routinely get involved in searching for data for students or studios, except in the case of core studios where the coordiators have made their needs known at least a month in advance. The demand for data searching is inexhaustible and often unreasonable. We will do our best to cultivate designers who understand how to compile their own resources.

The GSD's Geo Data Collection

Each term we try to gather together detaield datsets that have been gatherd for studios. This collection is stored on the shared network volume l:\public\geo. You can find descriptions of the datasets stored there in the Geo Catalog. If we don't happen to have the data you need, in our collection, or if it is not covered by one of the general sources listed above, then you will have to make some friends in the local GIS establishment in your area of interest. Please make sure to ask for metadata for the information you get, and please make sure that the data get archived in the GSD's data collection when you are finished!

Time Series Multispectral Sattelite Images

The NASA Mission to Planet Earth project has produced nicely georeferenced series of relatively cloud free imagery covering the whole globe. The imagery, which can be downloaded from The University of Maryland Global Land Cover Faciltiy, is of fairly course resolution (30-60 meter cell size) but contains higher spectral resolution than most imagery, with a channel for infrared reflectance. These multi-chammel images can be tricky to work with, but if you are very patient, you can meld the various channels into useful graphical products and even do some classification of land cover and land use change, see Classifying Multispectral Images

Source: http://www.gsd.harvard.edu/