Lab For Vector Analysis & Geoprocessing

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Vector Analysis & Geoprocessing

 

Introduction

This lab introduces conducting spatial analysis and geoprocessing in ArcGIS.  You will learn the following skills:

• Calculating statistics
• Selecting features with SQL
• Dissolving features
• Clipping layers
• Exporting data
• Buffering features
• Overlaying data
• Calculate attribute values

 

Instructions

Read Chapters 8 & 9 of GIS Concepts and ArcGIS Methods and answer questions in Part I.  Continue with the tutorial exercises in Part II.  You should copy any data you download from the course website onto your flash drive. 

As you read through Chapters 8 & 9, you should follow along in ArcMap and ArcCatalog.  You will be expected to use the text as reference for Part II – it will emphasize the application of tools introduced in the text.

 

Deliverables

Answer the questions (in bold) and produce requested outputs.  All labs should be typed, and well organized.  Email me an electronic copy of your lab in .doc or .pdf format with all outputs inserted in the document.

PART I: Single-Layer Analysis & Dual-Layer Analysis (pgs 323-368)

1.    What is geoprocessing and what feature in ArcGIS allows you to conduct these operations?

2.    ArcToolbox has an auto-documentation feature.  Why is documentation of your geoprocessing an important step in GIS analysis?

3.    When is batch processing useful?

Documentation of your analysis

When conducting GIS analysis, it is recommended that you create proper documentation of your datasets and analytical steps.  One way to document datasets is to edit metadata in ArcCatalog to provide data about your data.  Using the edit tool within the metadata window, add a brief explanation of the datasets you create. 

New datasets created through geoprocessing analysis carry the ‘history’ in the data quality section of the FGDC metadata style. I recommend keeping a document (word or notepad) that tracks the steps you take when conducting any analytical processing on your datasets.

PART II:  U.S. Urban & Rural Populations

Problem Statement:  In 2007 the world’s population achieved an unprecedented status: half the population now lives in urban areas.  Using 2005 census data estimates, you will figure out what percentage of US & state populations live in urban areas.

§  Download Wi11_Lab3 data from course website and add the counties and urban_dtl shapefiles into a new .mxd doc.

§  Take a few minutes to explore the datasets and get to know what kind of data you have to work with.

US Percentage

§  First off, you will notice that you do not have a dataset of the US as a whole.  You create a new dataset that summarizes all the information from the counties feature class into one country. 

§  Open ArcToolbox and navigate to the Dissolve tool (Data Management Tools>Generalization>Dissolve) or access the Dissolve tool via the Geoprocessing menu.  

 

1.    What is the function of the dissolve tool?

• Using the Counties feature class, dissolve all features (not on any specific field).  Make sure that you use the Statistics field tool to sum the attribute fields you need to solve the question in the problem statement. 

           

2.    What fields do you need to summarize in order to answer the question in the problem statement?

 

• Name the new dataset USpop (in Output) and click OK. 

• Add the new dataset to your map.

• Now you should have the population and area info for the whole US.

• Next, you will need to find out the population of all urban areas.  You could use the dissolve tool again similar to the steps you took in creating USpop, but you can also use the Statistics Tool in the attribute table to summarize data in an attribute field (pg 327).

• Open the Attribute table of Urban_dtl and right-click on the population field>Statistics

• Notice in the ‘Minimum’ count there are negative numbers.  To get an accurate sum of the population, remove all features that have a population less than zero.  You can do this a number of ways (Hint: definition query, export as a new dataset, select by attribute)

2.    What process did you use to remove all negative numbers from Urban_dtl?

3.    What percentage of the US population lives in urban areas?

4.    What percentage of the US land area is urban? (You will have to add a new field, calculate area, and summarize stats to answer this question – read the next few steps to guide you).

• To calculate the answer to #5, you will need to know the area of the urban areas.  You can calculate area, but first you want to see what projection the Urban_dtl dataset is in.

 

5.    What is the projection?

• Project your data frame into an equal area projection

6.    What projection did you choose?

• Add a new field in the Urban_dtl and calculate area. 

• Calculate the area of the whole US (in USPop) using the projection of the data frame.

• Using the Statistics tool get the sum area of all urban areas and the US, and answer #5.

State Percentages

• Use the Counties feature class and the dissolve tool to create a state feature class.  This time you will dissolve on the State_Name field.  Remember to use the statistics tool to summarize the necessary information in attribute fields by state.

• Next - to answer the question about individual states.  Using a Spatial Join (pg 365) you will create a new feature class that joins the urban information to the States attribute table.  Name this new dataset, States_urban.

  

• Look closely at your data – there is a problem with the spatial join.  Turn on your Urban_dtl and States layers.  Notice how some urban areas cover multiple states (NY/NJ, VA/MD, etc).  How was that handled in the join?  You can investigate the problem by using the Statistics tool in the original files. 

2.    Explain how you could correct the erroneous data created by the Spatial Join (look back to class lecture – Vector Analysis Part I, Areal Interpolation).  

• Go through the steps you describe in question # 8, making the corrections to the spatial join results. 

• When you have a final States_Urban dataset, add new (double) field to States_Urban, called ‘percent’. 

• Right-click on the newly created Percent field and go to Field Calculator.  Here you are going to calculate percent of urban population by entering in the formula for: (PopUrban/TotalPop2005)*100  (the actual formula will look slightly different – it will be based on your field names)

3.    How many states have an urban population greater than 50%?

Oregon Urban Map

• Next you will make a map of Oregon urban areas.  Open a new .mxd and add States (from last section) and Urban_dtl shapefiles.

• Zoom into Oregon and using the selection tool, highlight Oregon. 

• Export (just Oregon) as a new dataset.  Name it ‘Oregon’ (follow the two screen shots below).

  

 

• Add the new dataset to your map document. 

• Use the Clip Tool (pg 360) to create a new feature class that only contains the urban areas in Oregon

• In ArcToolbox go to Analysis Tools>Extract>Clip or access the Clip tool from the Geoprocessing Menu.

• The input is the Urban_dtl shapefile, and Oregon is the Clip Feature.  

• Save the output, OregonUrbanAreas, to your flash drive and add to your map document. 

• The clip eliminated Vancouver, WA, but it is closely tied to the Portland Metro area.  

• Write a definition query in urban_dtl to only display the Vancouver, WA urban area.

• Use the Append Tool (pg 364) to append the Vancouver, WA feature to OregonUrbanAreas. 

• In ArcToolbox go to Data Management Tools>General>Append

• The input is the urban_dtl, and the target is OregonUrbanAreas.

• The append tool changes the OregonUrbanAreas file – it does not create a new file.

• Use these files to create a presentation quality map of all Urban Areas in Oregon (including Vancouver).  Add label for the top 5 largest urban areas, including the name, population, and area.  

1.    Export as a .jpg and insert into your lab document.

PART III: Land-Use Regulations & the Urban Growth Boundary (UGB)

Problem Statement:  How many tax lots can be designated as rural reserves outside the UGB within Clackamas County?  Metro is in the process of designating rural reserves that have “high value working farms and forests or have important natural features like rivers, wetlands, buttes and floodplains.”  

“A rural reserve designation means that your rural land will not be considered for inclusion within the urban growth boundary for the next 40 to 50 years.”

You are going to find properties that meet the following criteria for their initial consideration as a reserve designation.

§  At least a mile from the UGB

§  Zoned as rural, forest, or agriculture

§  At least 25 acres

§  No building on the lot

Start by opening a new .mxd document and adding the Clackamas_taxlots (taxlots in Clackamas county) and ugb_fill (the Portland Metro urban growth boundary) feature classes.  Files for this section are a separate download from the course website (Part III).

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• To determine what properties are at least a mile from the UGB, you are going to create a 1 mile buffer with the Buffer Tool (pg 337).

• In ArcToolbox go to Analysis Tools>Proximity>Buffer or access the Buffer tool from the geoprocessing menu.

 

§  Save the output as ugb_Buffer and add the new dataset to your map.  We will come back to this dataset later.

§  Next, you need to determine what properties meet the criteria for size and designation. 

§  Open and look through the Clackamas_taxlots attribute table.  The table should include the owner and site addresses, land value, building value, occupancy, land use, sale price, and other attributes.

 

§  Use the landuse,  A_T_Acres, and bldgsqft fields to write a definition query to find the taxlots that are designated as rural (RUR), forest (FOR), or agricultural (AGR); at least 25 acres in size; and have no current building.  You will use the definition query to temporarily ‘hide’ any taxlots that do not meet our criteria for this analysis.

§  Go to the Clackamas layer properties and under the 'Definition Query' tab write the following query:  [LANDUSE] in ( 'AGR', 'FOR', 'RUR') AND [BLDGSQFT] <=0 AND [A_T_ACRES] >25

Your syntax may be slightly different (it changes when working in shapefiles and feature classes).  To ensure the syntax is correct, use the query wizard. 

 

1.    How many properties fit these three criteria?

2.    Create a presentation quality map that shows all the taxlots that meet this criteria.  Be sure to get some base layers for your map to put these taxlots into context.  Add a title, your name, scale bar, etc….all necessary map elements.

• Now – the final step is to determine what properties lie outside the UGB 1 mile buffer.  Use the Union tool (361-3) to combine the taxlot and UBG buffer data sets. 

1.    What is the difference between the Union & Intersect Tools?

2.    How can you use the attribute table to determine which taxlots fall outside the buffer?

3.    How many potential properties can be considered for inclusion as a rural reserve?

4.    What percentage of Clackamas county (use acreage) has ‘rural reserve potential’?

5.    Of the potential reserves, what percentage is rural? Forest? Agricultural?

• After you run the Union, look closely at the taxlots that are right on the border or cut by the 1 mile buffer. 

6.    How (if at all), will those ‘cut’ taxlots affect the results of your calculations?

7.    What happens if you change the size requirement to at least 50 acres?

8.    Create a presentation quality map that highlights the ‘rural reserve potential’ properties, differentiating between rural, agr, and forests, and has the acreage by land-use designation information (perhaps in table format).

PART IV:  Accessibility to North Portland Light Rail Stations

Problem Statement:  Tri-Met wants to conduct an analysis that determines how accessible people in North Portland are to the Yellow MAX line stops.  They came to you to conduct the initial analysis, which is to determine which taxlots are within a .5 and 1 miles from light rail stops. 

They have provided you with 4 shapefiles:

• taxlots: taxlots within the 97217 zip code
• taxlots97227: taxlots within the 97227 zip code
• lrt_stop: All Light Rail stop locations
• NoPoParks: Parks within the 97217 & 97227 zip codes

To complete this analysis, you will need to:

• eliminate all the parks from both taxlot files
• calculate distance from light rail stops to taxlots

To complete this project there will be 3 main tools that you will use: Append, Erase, and Buffer

• Start by opening a new .mxd and saving it as NoPoLightRail.mxd.  Add the four shapefiles mentioned above. 

• Since we have to use a few tools on both the taxlots & taxlots97227 layers, the first thing to do is Append one file to the other. 

• In ArcToolbox, go to Data Management Tools>General>Append (pg 364)

1. Explain how the Append tool works.

2. How is the Append tool different from the Merge tool?

• Since taxlots.shp has a more general name, we will use that as our ‘target’ layer and the taxlots97227 as the input data set. 

3. How did taxlots.shp change after using the Append Tool?

• Now you can remove the taxlots97227 from your map. 

• Next we can eliminate all parks from the taxlots file.  Tri-Met is interested in how acccesible the Light rail stations are to people - nobody lives in parks (except for the occasional vagrant), so we will eliminate.

• Use the Erase tool to complete this task.  In ArcToolbox, go to Analysis Tools>Overlay>Erase (pg 360)

• In the Erase tool wizard, set your input feature as the taxlots, and erase feature as NoPoParks (this way the parks will be erased from the taxlots layer). 

• Name the output taxlots_noParks and save to your flash drive.

4. Explain how the Erase tool works.

• Next, use the multi-ring buffer tool to find which and how many taxlots fall within the .5 & 1 mile radius from the stops. 

• In ArcCatalog, go to Analysis tools>Proximity>Multi Ring Buffer

• Using the Lrt_stops as your input feature, create a .5 & 1 mile buffer around each of them.  If you wanted to make processing time faster, you could select the stops within the project area and create a new file (this can be done a few different ways). 

5. What is one way to isolate the light rail stops within our project area?

• Create a map (or multiple maps) that identifies the taxlots that are within .5 & 1 mile from each stop, as well as the land-use type of the taxlots that fall within the buffer. Do not forget to add titles, legends, etc. - presentation quality.

6. How many taxlots are SFR & MFR?
7. Can you think of a way Tri-Met could estimate # of people based on the information provided in the taxlots attributes?  Explain.
8. Export your map as a .jpg and insert into your lab document.