321_F17_Mastery_Exercise 2
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Feb 20, 2024
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1 Mastery Exercise 2: Database Query, Table Join, and Calculation Database Query and Field Calculation Introduction This section of the mastery exercise focuses on using ArcGIS for database query, table join, and field/variable calculation. To do the exercise, you should have the following data layers: Data for all of New Jersey: o
Municipalities and census data for New Jersey (NJ_Municipalities.shp) Data for the Hackensack River Watershed: o
Landuse (Hackensack_Landuse.shp) o
Municipalities (Hackensack_Municipalities.shp) o
Streams (Hackensack_Streams.shp) o
Lakes (Hackensack_Lakes.shp) o
Roads (Hackensack_Roads.shp) o
Factory locations (Hackensack_Factories.shp) o
Public school locations (Hackensack_Public_Sites.shp) The objective of this section of the exercise is to answer several questions concerning population, landuse, etc. in the Hackensack watershed which is in Northeast New Jersey. The steps below cover both database query and field calculation forms of analysis. Follow the steps and briefly answer all questions. Explore the Data (Spatial and Attribute) and Calculate New Attributes o
Display the municipalities for all of New Jersey (NJ_Municipalities) and for the watershed (Hackensack_Municipalities). o
Note the absence of census information for year 2000 in the Hackensack_Municipalities data layer. o
Join the attribute tables of these layers so you can explore year 2000 census in just the watershed area. Question 1: Describe the overall pattern of population in 2000 and population density in 2000 in the watershed. What type of color scheme and classification method worked best for each attribute? Why? What are the names of the most Northwestern and most Southeastern municipalities? What were their populations and population densities in the year 2000?
2 You can easily calculate the average (and other basic descriptive statistics) for any attribute/field in an attribute table (for any data layer) using the Statistics function
. See Lesson 6 for details related to this operation. Question 2: For the year 2000, compare the average (mean) population density of municipalities in the watershed with the average population density of the entire state of New Jersey. What is the average population density of municipalities in the watershed? In the state? Is the watershed area more or less densely populated than the state as a whole? There is another function available to you that can help you to explore your attribute data. This is the Summarize function
. See Lesson 6 for details related to this operation. Calculate the area of each feature in the Hackensack_Landuse data layer. Summarize the values in the new field containing the area calculation for each unique CLASS in the Hachensack_Landuse attribute table. Question 3: How many square miles does each landuse CLASS cover in the Hackensack watershed? Which landuse CLASS dominates the watershed? Question4: Using the Summarize function again figure out which CITY has the most factories. Which city has the most factories? How many? Database Query and Table Join Use query by attribute and table join to answer these questions. When joining, recall that a common key (with matching data type) is needed to join tables. See Lesson 5 for details related to these operations. Question 5: Which municipality in the watershed has the highest population in 2000? What is its area in square miles? What is its population density for the same year? Question 6: What are the names of the municipalities that have populations in 2000 greater than 35,000 and are smaller than 1.5 square miles in size? Calculate change in population and change in population density from 1990 to 2000 Create two new fields based on the data for municipalities in the watershed: one for the change in population from 1980 to 2000 and one for percent change from 1980 to 2000. Question 7: Which municipality experienced the largest increase in population from 1980 to 2000? Which had the largest decrease? Which municipality had the largest percent increase? Which had the largest percent decrease?
3 Database Query based on Spatial Relationships The goal of this section of the exercise is to make a map showing both the threats to the Hackensack River and opportunities for improving recreation and environmental experiences. The map will be made up of new data layers which are specific to the river. It will require that you query your data based on the criteria listed below and that you save the data you have selected as new data layers. Once all layers are saved, you will compose them into a coherent map. The new map will display the following elements: Basic data which will give context to the Hackensack River: o
Those line segments from Hackensack_Streams which actually make up the Hackensack River. o
Water bodies through which the river runs or connects (from Hackensack_Lakes). o
Municipalities containing or bordering the Hackensack River. Sites that pose a potential threat to the river due to pollution: o
Factory locations within .5 miles of the river. Sites that suggest an opportunity for improved recreation and environmental awareness: o
Known recreational land with .5 miles of the rivers. To select from all Hackensack_Streams only those which make up the Hackensack River recall that when developing a SQL you can not only search for numeric values but for specific strings of characters as well. Examine the attribute table for Hackensack_Streams and note that there are many line segments labeled as HACKENSACK RIVER and that some have addition information after the name of the river. In this case, use a percent sign as a “wild card” denoting any possible character and use the LIKE function rather than “=” to search for strings which contain characters you want to find but which may contain additional characters too. Once you have selected the Hackensack River from all Hackensack_Streams, save the selected data to a new file by right clicking on the layer name, choosing Data and then Export Data. Export the selected features to a new file with a name that makes sense to you (retain the SHP extension). Be sure to save the new file in an appropriate directory. Once you have selected those segments which represent the Hackensack River, select the water bodies (from Hackensack_Lakes) through which the river runs. Also save those as a new file. Now select those municipalities which contain or border the Hackensack River. We are interested in these municipalities because their activities or ordnances might directly affect the quality of the river. Question 8: What Spatial Selection Method did you use to find all water bodies through which the river flows? What Spatial Selection Method did you use to find municipalities
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4 which contain or border the river? Note that there are some municipalities in your result which clearly do border the river but which are not selected (e.g. zoom in on Rutherford Boro). Modify your Spatial Selection Method such that municipalities like Rutherford Boro (i.e. those that seem to “really” border the river) are included in your selection (but those which are distant from the river are not selected). Save these selected municipalities to a new file (as you did above). Finally, select factories that are within a half mile of the river as well as recreational lands which are within a half mile of the river. Save both the factories and the recreational land to new files. Now you are ready to make your map. Question 9: What was the Spatial Selection Method you used to find municipalities which actually contain or border the river? Which municipality contains the most factories (and how many) within a half mile of the river? How did you find the number of factories? You should find this result using tools covered in class and not just simple visual inspection. Question 10: Make a map depicting the Hackensack River, the water bodies through which it flows, and the municipalities which contain or border the river. Display population densities for the year 2000 for the municipalities on your map. Add to the map the threats (nearby factories) and potentials (nearby recreational areas). Use appropriate color schemes and symbols and print in color.