Beginning your Place-Based Data Collection

Most every design project considered at the Harvard Graduate School of Design has a site; each site has context. One task in beginning a design project is to gather information which will help the designer and his/her clients understand the site and its context. This tutorial provides instruction for finding and assembling basic geograpghic information for the purpose for understanding and portraying basic site context. In addition to being useful for the production of basic maps, these basic contextual layers will provide a framework for more complex thematic maps and anlytical studies; and as a setting for new information created in the design process.

Big Ideas in this Tutorial

• GIS Datasets represent measurements and observetions of entities made with a specific purpose in mind.
• Metadata is an essential element of a collection of place-based data
• Portrayals: e.g. Layers and Map Documents reference datasets through file-system path references
• Structuring collections of GIS data, metadata and portrals so thait the relative path references among the portrayals and datasets remain stable is of critical importance for making a collection of resources that is shareable and reusable on different computers.

Objective:

After studying this tutorial, you should be able to begin your place-based data compilatioin using datasets from the internet and the GSD data collection. Your dataset should ve well structured and well docuymented to support collaboration by a team of designers, and archiving for use in future projects.

Sample Dataset

Click here to download the sample dataset. Create a folder for yourself in your c:\temp folder, and expand the zip archive containing the sample dataset into this folder.

Background Information

• GIS Data Resources
• Rhode Island GIS
• Understanding GIS Data and Metadata
• GSD Metadata Tool
• Lecture Notes on GIS Data, Metadata and Portrayals

Software User Guides for Deeper Reading:

• What is ArcMap
• Using ArcMap
• Using ArcCatalog

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A Stable Structure

Our problem today is to learn to gather data to help us understand and organize ideas about a place. Looking forward, this collection of data will grow and be connected with maps and models and we will want this arrangement of information to be structured so that we can easily keep it backed up and share it with other collaborators who will easily be able to find what they need, to use our collection and to extend it without messing it up.

Our compilation may include several types of data, including site photos, 3d models and others, as well as the final presentation documents that we create. Each sort of data in the collection may have been collected from different sources, or generated by a different collaborator working on the project. In anticipation of this, our collection will grow according to the following structural principles:

Collection Folder

All of the data and documents we collect will be contained in an Outer Folder named for our site or project.

Our folder will contain a Metadata File that explains the purpose of the collection, and when it was collected among other things. The collection may have subfolders for various types of data. The collection also contains a Documents folder named docs that contains the presentation documents and master map documents created for the project.

The metadata in the various folders in this collection can be made with the GSD Metadata tool Here are examples for the Overall Collection Metadata and the Compilation of data from Rhode Island GIS.

GIS Data Folder

The GIS Folder in our collection has subfolders to hold data from different sources.

Each source folder has its own Metadata File that explains the source of the data, and when it was collected among other things. In addition to holding GIS Datasets, each of these may have dataset-specific metadata and dataset-specific Portrayal Information. Within each application-specific folder, there may be working folders for each project collaborator containing working data, documents and tools created by that user.

This structure provides a predictable means of understanding where each piece of data should go when it is collected, and where it may be found later. It also allows the project collection to grow in terms of the number of collaborators and derived datasets without becoming unmanageable. Before the project compilation is shared, user data considered to be intermediate can be cleaned up. User documents that are to be shared with the project may be moved to the Project Documents folder.

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Getting Started with AcrMap and ArcCatalog

To begin, we will launch some tools created for working with spatial data. ArcCatalog is for creating and managing data and metadata, ArcMap is for visualizing and transforming GIS data. For more information, look at the user guides referenced at the top of this page, and these documents from the on-line help for ArcGIS:

ArcMap Documentation

• Workspace and Dataset Management with ArcCatalog
• Adding Layers to a Map and other documents under the heading Working with Layers
• The ArcMap Tools Toolbar
• Elements of Geographic Information
• Using ArcMap Chapter 10, Working with Tables

Creating a Portrayal: Working with ArcGIS Layers

Our Loccons layer is useful. But it is not so easily understood on a map. What can we do about this? First, we can change the name of the layer to something more meaningful. Second, map readers expect parks to be green, so we can alter the symbology of the this layer to shade all of the polygons green. Next, we will alter they label properties to label each park with its name. Just for fun, we will play with the scale-dependent display properties of this layer to cause it to dissappear when we zoom way out. All of this is portrayal information, which is independent from the data itself. There may be 1000s of different ways to portray a dataset, depending on what we are trying to communicate (or to hide!). ArcMap lets us save this portrayal ionformation in a Map document or in a separate layer file.

ArcMap Documentation

• Changing a layer's drawing order
• Changing a layer's text description
• Setting layer properties
• Displaying Labels
• Displaying layers at certain scales
• Saving a Layer to Disk

Once we add the layer we saved back to the map, it is very important to examine how the layer file relates to its source feature class by looking at the layer's source property.

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Extracting a Subset of Features from a Large Feature Class

The Rhode Island GIS Local Conservation layer of parks information for our map. But we don't need all of the parks in Rhode Island. We want to keep our data collection focused on our area of interest and its greater context. If we aren't careful, we will end up with gigabytes of data that aren't of any use to us and our collaborators. So we will export a subset of these features to our compilation folder.

ArcMap Documentation

• Exporting Features
• Referencing Data in Maps
• Reparing Data Source Links

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Copying Datasets with ArcCatalog

Sometimes we may want to copy an entire dataset from our downloads folder into our compilation. For this we will use ArcCatalog.

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Saving the Metadata for your Layers

We need to make sure that we save the metadata from our source data into our data compilation folder. For some types of metadata, ArcMap will copy the metadata for us when we export the features. For others, we will need to use Windows explorer to do this. We can also use the GSD Metadata tool to create metadata as needed.

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Absolute and Relative Path Names

The Map Document and its Layers are Portrayals that Reference Datasets using Filesystem Paths. These path references may become invalid if the map document or the data are moved. Since we want our data compilations and maps to be portable. This is considered a BAD THING.

Absolute, or Full Path References are specific about what disk data are on. They will work even if the map file is moved. If the data are moved, however, an absolute reference will Absolute Reference will become invalid. Relative Path References remain valid if the map document and the data are moved together but maintain the same relative positon within a folder context.

Therefore, if we want to be able to move our data from one computer or disk to another, we need to learn how to maintain a stable relative relationship between our map documents and our data and to store relative path references in our map documents.

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Saving your Map Document with all of its Portrayals to your Compilation

You have seen how layer files save portrayal information. It is also possible to save the whole map document with all of its layers to the docs folder of our compilation. To make sure that the compilation will work on another copmputer, we need to make sure that the map documents in our compilation folder do not reference datasets that aren't part of our compilation. For this, we will use the Source View of our ArcMap table of contents to view datasets according to what folders they reside in. Using this view we can eliminate any of the layers that are not in our compilation's gis folder. Then we set the Data Source Properties in ArcMap so that the document uses Relative Path Names to reference its data sources. Then we save the map document into the docs folder of our data compilation.

References:

• Referencing Data on the Map
• Thew ArcMap Table of Contents
• Pathnames explained: Absolute, relative, UNC, and URL

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Conclusion and Your Assignment

You now have the fundamentals of working with ArcMAp and organizing a concise and complete data compilation! Now you should now find an area that you are interested in for your class project, investigate datasources that are available on the web, and begin your compilation, focusing first on thjose layers that will be useful for portraying the basic context of your site. One very good set of data and portrayls will be the ESRI Maps and Data CDs that ship with the ArcMap software.

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ESRI Streetmap is a product that makes it very easy to make maps of anywhere in the US. Streetmap is a single CD which contains a very elaborate system of GIS data that has been packaged in a hierarchical set of ArcGIS layers which get more detailed as you zoom in. This provides a very easy source for GIS data at many scales.

Users at the GSD will find the ESRI Streetmap CD shared on the network at:

  l:\public\geo\esridata_9 

Collecting data from streetmap or the other esridata products uses all of the techniques covered in this tutorial. There are a couple of additional tips that you will find useful:

References:

li>Managing Group Layers

Displaying Layers at Certain Scales.

Adding a Folder to your ArcGIS Catalog

To load ESRI Streetmap you may need to use the Connect to Folder button.
Street Reference streetmap has almost every street in the country.
Other layers, like hydrography appear as you zoom out.
At the Regional Scale you have more general detail.
On out to National-Level of detail.

International and Other Data

If you are interested in data that is not on the ESRI Streetmap CD, such as the locations of schools and hospitals in the US, or basemap data for Europe, or general basemap data for the rest of the world, you should check out the data layers provided with ArcGIS in the ESRI Maps and Data CDs. Click here for a listing of the layers available on these CDs.