LAB 2b
Problem - we want to
build a power plant. There is a property for sale that has good potential for a
building site. However, we do not want to build on soil contaminated with more
than 100 ppb mercury or arsenic with values greater than 150 ppb, nor do we
want to build within 1500 meters of such contamination.
Download the file at the bottom of the page and save it to
your hard drive. In Catalog, locate the file, right-click on it and choose
"Create Feature Class" from the context menu and then "From XY
Table". Then select your XY fields X field should be Long
(longitude) and Y field should be Lat (latitude). Click on
"Coordinate System of Input Coordinates" and
define your coordinate system - click on Geographic Coordinate Systems
(we are using Latitude and Longitude), select Spheroid Based Clarke 1866 prj.
When saving, specify the output shapefile
in the folder for Lab 2b and select to save as a shapefile
in the bottom window where it says Save as Type:
Down-load this zipped shape file -
Potential Property and add it to your Map
document.
The two files together should look
like this:
2a. Run a query on your shape file containing soil
geochemistry data. To do this use the "Selection"
pull-down menu located in the main menu at the top of the ArcMap screen and choose "Select by Attributes. We did
this in Lab 2a to identify the Section “15”. Build this query - "Hg" >= 100 OR
"xAs" >= 150. Double click on
"Hg", single click on ">=" no space type in 100, double
click on "OR" Single click on "xAs"
single click on ">=" no space type in 150. Your selected sites
will be in turquoise.
The map after the selection should
look like this:
Now close the query window and open the “Toolbox".
It is the icon that has a red tool box. 
Once the “Toolbox” is expanded, select "Analysis
Tools" and then”Proximity” then "BUFFER."
(You will also find the "Buffer" tool by clicking on the Geoprocessing icon in the main toolbar in the top
margin). Select the appropriate layer and output location. In the Distance box,
the linear unit will be checked, add a distance of 1500 m, where it says
Dissolve, select "ALL" in the drop down menu and go with the default
with all other options.
The output should look like this:
To qualify for purchase, two-thirds of the property must
fall outside of our contamination parameters. Does the
property meet this criterion? Do we buy or look elsewhere?
To make sure, return to the “Toolbox” and under
Analysis Tools select “Overlay” and use the “Intersect” option.
Use the buffer shape file you created and the Property shape file as input - go
with the default settings. This will create a new polygon showing only the area
that overlaps.
The output should look like:
You must now re-project
the new intersect shapefile (it will automatically be
added to the Table of Contents and will have the word “intersect” at the end of
the shapefile name) from latitude/longitude to UTM
Zone 11, NAD 83. To do this, go back to the “Toolbox” and choose “Data
Management Tools”. Then go down the list to “Projections and Transformations”
and choose “Feature” > “Project”.
Follow the steps in the Project box, name the new shapefile saving it to your Lab 2c folder, specify the UTM
projection and click on OK.
Re-name the file so you can tell it has been re-projected
to UTM, I add utm to the end
of my file name. Next re-project the Property shapefile
to UTM Zone 11, NAD 83 using the same steps as above.
You will now need to open a new map document so there are
no coordinate system conflicts. (Remember that the units in the bottom right
will reflect the first shapefile or data layer added to ArcMap.
In this case it was a Geographic Coordinate System and the units are in Decimal
Degrees)
Add your re-projected shapefiles
and add a new field to both called “area”. Then calculate the areas for the two
polygons as you did in Lab 2a. You can then calculate the percentage of the
area that is contaminated using a calculator.
2b. Create a map. Your
shapefiles should look like this:
Center the property and adjacent high mercury/arsenic areas
(buffer area). Place an appropriate title, legend, north arrow, scale bar and
measured grid (click on "View" and in the pull down menu and choose
"Data Frame Properties". Click on Grids and New Grid and Measured
Grid. Go with all of the defaults and the grid will show UTM coordinates in the
margins when it is applied). NOTE: do not add a neatline, the grid tool will
do this for you. (add your suggestion whether to
buy or not). Send the map as a jpeg or pdf by the due date.