The next set of labs for people on the urban planning track will all use the same data set. The data exists as a set of Arcinfo coverages at this location:

N:\LABS378\fitchb

The instructions for these labs are much less detailed than the first set of labs because you should not have to be "walked through" the commands, menus and buttons to do the tasks. To help you out a little I have included in brackets the previous labs where you did work like this so you could go back to the lab and figure it out. But what I really want you to do is to become a little more adventurous with the software and seek out what is behind the buttons and menus.

These labs are not designed as units. As soon as you have completed the tasks e-mail me your reponse. This may be the location of a map file for ArcGIS, a table you created, etc. During lab time I will be around to trouble shoot and help you find things but if you ask for help, my first question will be "Show me what you have tried already." In other words, I want you to fumble around the data and software for a while before you call me over and be able to explain what you have done so far. Remember - you cannot hurt the data or the software. The worst it will do to you is tell you it can't execute the command you want it to. So… have fun!

Files needed: You will need the Zoning.e00 and Ward.e00 files for this task. You will find them in N:\labs378\fitchb.  Create a workspace for yourself, copy the export files in and import them to make them coverages.

The planning executive director is having a set of neighborhood meetings by ward around the town. Everybody likes to have data customized for their area and GIS is an excellent tool to do this. You have been asked to prepare some tables showing how much of each ward is covered by each zoning category. You will have to create a new field acres and calculate that field based on zoning (there are 43560 feet in an acre).  As in Core Lab 2 you will use the summarize option (open the table, highlight the zoning category field and choose summarize)  to add up the square footage of each zoning category, convert them to acres, use Statistics  to find the total number of acres and then calculate the percentage.

A. ENTIRE CITY

B. Acres of Zoning  By Ward

Because some of the zoning polygons are very large they intersect many different wards so just selecting a ward and doing a spatial query  and then summarizing the acreages is going to give you some weird results.  If one corner of a large zoning polygon intersects a particular ward, the entire zoning polygon is selected and that is not what we want. One zoning polygon may intersect more than one ward and would be counted in both.

As with many problems, there are multiple ways to solve this.  Choose the one from the list below that you want to work on.

1. Using Spatial Analyst - create grids of zoning and wards. Grid them as 50x50 ft grid cells and make sure you cover the entire city and use the same theme as the spatial extent for both grids.  The process you will have to use will create a lot of grids so make sure you keep track of them and give them informative names; it is very easy to fall into the trap of using default names and the not knowing what is what.  You will need to assign a number to each zoning category and to each ward because when you use the map calculator to multiply them together (as you did in Core Lab 2) you need numbers since the multiplication of 1A * CBD is not a defined multiplication.

Make a separate grid for each ward using a 1 for a cell if it is in the ward and No data if it is not,  and multiply that times the zoning grid (using a number for each different zoning category).  So if RA1 is the 10th different zoning category in the grid of zoning, each cell in that zoning area has a value of 10.  And if you are working with ward 1A, all grid cells in that layer that are in ward 1A have a value of 1 and those that are not have a value of no data.  The resulting map calculation of zoning times ward 1A will give a grid with counts for each zoning category.  Then you will calculate square footage and acreage as above.

2. Intersecting the Coverages with Toolbox

If you have access to Arcinfo it is the easiest way to do this.  The UNION command is found in the ArcToolbox Analysis set of tools.  Specify one of the coverages as the input coverage and the other as the union coverage.  This will create the union of these two coverages (the area covered by both coverages) with the attribute information of both attached. The area for the union polygons (all the unique Ward/Zone combinations) will be correct. This data is a good case study of the problem of slivers in overlay.  Because the zoning and wards polygon layers do not match up exactly where you would think they would, there are many slivers in this resultant unioned coverage.  Look for small polygons, smaller than 500 square ft. We are not going to fix this in this exercise.

To calculate the areas of zoning categories for each ward you will first need to calculate the acreage for each polygon in the union coverage. Add a new field called acreage (from the options button in the table) make it number, 8 columns wide, 3 values to the right of the decimal point. Calculate Acreage = Area / 43560.  Then you select the wards, one at a time [Use the query builder], highlight the zoning category field.  Use the Summarize option with Field: Acreage, Summarize by: Sum.  Add this to the table (make sure the table will be saved in your lab workspace) and click OK.  This will complete one row of the table. Do this for each ward to complete the table. If you want to learn how to do this in one step in MS Access, call me over.  ArcGIS cannot do cross-tabulation queries.

                         Acreage Table to be completed.

Turn in...

1. The location of your project. Make sure all objects such as views, tables, etc. have real names and not view1, etc.

2. A printout in Excel or just on paper of the three tables. If you have created a spreadsheet, e-mail that to me as well.