CEE 424
GIS for Civil Engineers
Homework 4 Answers
- When asked to print a screen shot, capture the screen and paste it to the document. Crop the image to show the map only. No need to add any other elements to the map.
- When asked to print a layout, add as much as you can of the following: Your name, Class #, north arrow, a scale bar, a scale text, and a legend. All are under “insert” when in layout mode. Shadows and borders can be inserted by “NeatLine” under “Insert”.
- I will ask you to answer several questions at a certain step of the exercise. To save time, always check at what step should you answer the following question.
Section 5: Analyzing feature relationship
Chapter 10: Selecting Features by Location
10-1 What are the four main spatial relationships that can be used in ArcGIS when selecting features by location?
Answer: Distance, containment, intersection, and adjacency.
10a: using location queries
10a-1 After step 11, change you selection to “neighborhoods that completely contain shopping centers”. Did that make in difference?
Answer: No, usually polygons totally include point features. Contain and completely contain work the same way most of the times when selecting polygons that include point features.
10b: Combining attribute and location queries
10b-1 What is the area of the building you selected at the end of the exercise?
Answer: Can be 4596.26 ft2, 4635.78 ft2, 5530.26 ft2, or 5993.65 ft2. Click on the “identify icon” and click on the building.
10b-2 What is the difference between “join” and “spatial join: in ArcGIS?
Answer: Join is an operation that joins attributes from two different tables based on attribute values. Spatial join is an operation that will join attributes from one layer to the attributes of another layer based on spatial relationships
10b-3 After step 25, close and re-open the exercise. Use spatial join to produce a map of the census tracts classified according to their distance from shopping centers. Print a screen shot of the map after you add your name to it. Your map should match the following map (show the legend):
Answer
1-Restart the exercise, clear the selected features, under select.
2-On the census tracts to display them and uncheck the neighborhoods.
3-Right-click on census and tracts, joins and relates, then join.
4-In the first drop-down menus, select: join data from another layer based on spatial location.
5-In the second drop-down menu, select shopping centers
6-In number 2, select the second option, and press OK.
7-Classify the new “join_output” layer according to distance:
a-Double click on the layer name, in the properties table, click on symbology.
b-Select “show” “categories”, then “unique values”
c-Add all values, then apply, OK
8-Finally, add your name and print the map.
Chapter 11: Preparing data for analysis
Exercise 11a: Dissolving features
11a-1 What is a “dissolve” operation? “dissolve is also called aggregateing and summaeizing”
Answer: Dissolve is and an operation that dissolve features that have the same value of an attribute specified by the user.
11b-2: After step 12, classify the layer “leases” using “graduated symbol”. Print a screen shot similar to the one below
Exercise 11b: Creating Graphs
11b-1 After step 11, save your graph as a .BMP image. Print the image.
Answer:
Go to tools, graphs, click on “lease values”, that will open the graph. Right click on the title bar and select: export, save as .bmp. Here is how it should look like:
11c: Clipping layers
11c-1 When clipping a layer, you name a “clip” layer and a “input” layer. After clipping the input layer by the clip layer, the attributes of the input layer and the clip layer change. True or false?
Answer: False
Exercise 11d: Exporting data
11d-1 After step 15, close exercise 11d and reopen exercise 11c. Use selection by location to produce two layers: streams selection and leases selction. The two layers should show the area F in the leases selection and the streams within area F in the streams selection. DO NOT CLIP ONE LAYER BY THE OTHER.
Answer:
1- set the selectable layer to: streams, under select, then select area F.
2- create a layer that includes only F “right click on leases, selection, then create layer from selected features.
3- under selection, choose select by location, select features from streams, that are contained within area F “the new layer by default was called leases selection”. Here is how it should look like:
Chapter 12 Analyzing spatial data
12a: Buffering Features
12a-1 After step 20, assume that another restriction applies. No logging is allowed within 100m from the lease boundary, inward. add a buffer “setback” at a distance 100 m inside the boundary of leaseF, show all buffers and print a screen shot.
Answer: tools, buffer wizard, buffers of layers: leaseF, then next.
Buffer at a specified distance 100m, then next
Accept to dissolve barriers, create buffers so that they are only inside the polygon, then finish. Here is the map:
Exercise 12b: Overlaying Data
12b-1 What features can be included in union and intersection operations?
Answer: Union is possible only between polygons, while intersection can be carried out between polygons or between a polygon and a line.
12b-2 What is the difference between union of polygons and dissolving them?
Answer: Polygons that share an attribute can be dissolved to form one larger polygon. The output of a dissolve operation is clusters of polygon that share the same attribute. Union does not require a common attribute and it will result in one layer that include several small polygons. The polygons are divided into several combinations, but united in one layer. Union results in many more polygons than dissolve. In other words, union will increase the contents of data while dissolve will reduce the contents of data.
Also, dissolve is an operation based on attributes while union is an operation based on location {spatial operation}
12b-3 After step 20, print a screen shot.
NOTE THAT THE ABOVE SCREENSHOT COMES FROM ArcGIS 9.3. This will be a little different in the Arc 10 version
Exercise 12c: Calculating Attribute Values
12c-1print a screen shot of the statistics of “final”.