EXERCISE 7 – BASIC ANALYSIS:
MAP ALGEBRA AND OVERLAYS

The Lawrence Brook Watershed turns out to be a relatively small watershed, about 46 square miles. Its boundary (give or take) is in the coverage lbw (Y:\intgeo\classwork\avdata\lbwpuse\). Let's imagine that the watershed group there want to build a new environmental center somewhere within that boundary. And let’s try to put off using ArcMap as long as possible.

They figure it should be accessible, so lets keep it within 200' of a road.

Use ArcToolbox/Coverage Tools to Buffer the roads (Y:\intgeo\classwork\avdata\lbwpuse\lbwstreets) of the watershed by 200 feet. (Call it rdbuf200)

But as an environmental center, it shouldn't be too close to a road. Let's keep it at least 50 feet away from a road.

Use Coverage Tools in ArcToolbox to Buffer the roads of the watershed by 50 feet. (Call it rdbuf50)

Take a peek at the buffer coverages in ArcCatalog and you'll notice that each has field called Inside. The polygons with values of 100 are inside the buffer, those with a value of 1 are outside. If we combine 2 files that both have fields called "INSIDE", something has to give. So, instead, we'll make sure they each have unique names.

Now, let's combine these two different coverages to make a single coverage from these two coverages.

In ArcToolbox, Union the two buffer coverages. (into rdcomb)

The "chosen site" needs to be on land that is not already developed but can developed. Sounds like we need land use information, so let's combine the landuse and the road buffers.

In ArcToolbox, Union landuse and rdcomb. (into lbwmess)

That still doesn't seem so specific, so let's say it should be within 500' of a stream. After all, it IS a watershed group.

Use ArcToolox to Buffer the streams coverage of the watershed by 500 feet. (Call it streambuf500)

Using ArcCatalog, change the Item name from INSIDE to INSIDE500.

In ArcToolbox, Union lbwmess and streambuf500 coverages. (into lbwtotal)

So, let's see what we've got. The lbwtotal is a bit frightful. Let's try restricting the polygons to just those that meet our criteria. We can do this using the Select tool in ArcToolbox. Unlike in ArcMap, when you use the Select command in ArcToolbox you create a new coverage with based on your query. You will probably want to use the "subset" option to build your query.

Preview the data in ArcCatalog. Do you still have some options? How would you pick? What if we only looked at the largest sites?

What if the tiny slivers of sites our analysis left us with were deemed unsuitable? Could we create a larger scoring system that describes the entire watershed?

In ArcCatalog, Add the following fields (as integers) to lbwtotal:

Landscore

Streamscore

Rd50score

Rd200score

Totalscore

Now, you can finally fire up ArcMap!

Open the attribute table and Select all of the polygons whose INSIDE500 = 100. Then Calculate the streamscore = 10 for all of those. The calculation will be performed only on the selected records.

Repeat this for each of the roads buffers. Make to sure select those polygon outside the 50 foot buffer and those that are inside the 200 foot buffer.

For the landuse, make the forests (LUCODE=4) a 10, the farms (LUCODE=2) a 7 and the rest a 2.

Clear the selection, then calculate an additive total (i.e., landscore+streamscore+rd50score+rd200score) in the totalscore field. Use the totalscore field to view the coverage with a graduated color scheme. (It'll look better if you eliminate the outlines around the polygons.)

For a different view, we can differentially weight the criteria, allowing us to stress the more important ones and downplay the less important ones. Calculate an a weighted total (i.e., 5* landscore+7*streamscore+2*rd50score+3*rd200score) in the totalscore field. Take a look at the results in ArcMap using a graduated color scheme.

What would happen if you used a different set of buffers? What if you "scored" areas as more suitable or less suitable, instead of discarding all areas that are unsuitable? What if you introduced some address-matched data, like nearby schools? What if you tried to locate the center near wetlands or lakes? The criteria you could use for choosing sites are limited only by the available data.

Develop a site-selection system for the environmental center. Hand in a map showing your selected site. You must use different buffers than we used AND you must use at least a little address matched data. Use the street (not street.mxc) Geocoding service in Y:/intgeo/rowan/avtrn/middlese/. You must also use a weight and rate system, not just an additive (or subtractive) scheme. Your map MUST be black and white and should clearly explain your rationale and scoring on your map.

Hint: To make the computing faster, you might still "mask" out some basic areas that are completely unusable (like all developed lands, or all recreation properties).

Namtrac Food Products, Inc. has developed a frozen bag of sugar-coated veggies that kids love called Kenny's Little Kernels. However, to make it a profitable venture, they figure they need to produce and sell their product entirely within a single country. They've asked you to help pick that country. But since they would also consider expanding to many other countries (without shipping product across borders) you should provide a scoring system that ranks all countries in the order that they might proceed.

"Well," you thought, "What would improve their chances of success?" A business book you found suggested:

a) strong customer base and

b) good production capability would be key.

Copy the demog.dbf file from Y:\intgeo\classwork\avdata\world\tables into your directory so that you can modify it. If you so choose, you can copy the whole world directory.

ONE solution would work like this…

Add some fields to the table and save it under a different name.

Calculate a "score" from 1 to 3 in each of the new fields to reflect the degree to which the record satisfies that condition (criterion). Some demographic data which might be useful include: Long life expectation (b - good production capability), High population (a - strong customer base), Stable Growth Rate (a), Lots of kids (a), and High convergence of ag. and urban land (a & b).

Add a field for the total formula score and calculate the formula score with weights included. While you are at it, add a few different fields, and try a few different formulas.

Save the edited table.

Join/relate it to the world attribute table and map it.

Come up with your own global solution. You don't need to limit yourself to factors (a) and (b) above, but at least some of your scoring criteria should reflect the importance of these factors. Maps will be graded in part based on their readability and composition. PRINT ONE BLACK AND WHITE MAP. It should be highly communicative. What were your criteria? What is your final decision?