1

I'm a total amateur at ArcGIS for Desktop, this is the first time I use it for real. The thing is I have several shapefiles with information about:

  1. Schools in my city (elementary, middle and high school)
  2. City districts

The schools' information has Points that represents the unit (the place itself) and also a Buffer (influence's radio of every unit). ONE LAYER BUT SEPARATE SHAPES (One for point one for buffers).

So, I need to cross this information so I can generate data that tells me the districts that are best equipped with each kind of educational level. I mean, which districts have more coverage of elementary schools, more coverage of middle high schools and more coverage of high schools. Even if they don't have any school within, but just some coverage from any buffer.

I don't know if I explained myself very well, but I'll be so thankful for any advice. I think I must merge the schools and then join this shape with the districts... (From what I've learned in my two days ArcGIS experience)

2

Given what you have described I would say that it sounds like you don't care which specific school covers a district, you only care about the type of school (elementary, middle, high) and the percentage of coverage of each school type relative to the total district size. Assuming the buffers contain a field representing the school type, I would approach the problem this way:

  1. If these are shapefiles, add 3 double fields to the District shapefile called curr_area, orig_area and area_percnt. Use the geometry calculator to calculate the curr_area and orig_area values to be the area of the districts. You will calculate the area_percnt value later.

  2. Use the Dissolve tool on the school buffers with the school type as the dissolve field and keep the default Multi-Part option to create a single feature for each type. You can summarize any other information you like from any other fields.

  3. To simplify analysis of the outputs, select each school type feature individually in turn and repeat the next steps with each school type feature naming the output files with a name referencing the school type.

  4. Use the Union tool with the Districts and the dissolved school buffer feature currently selected. If at step 7 you discover you have more than one final shape covered by that school type within any given district you may need to run the Dissolve tool at this point with the district and school type FID fields as the dissolve fields.

  5. If the output is to a shapefile, use the geometry calculator to update the curr_area values of the Union output.

  6. Calculate the area_percnt field to be equal to the curr_area/orig_area * 100.

  7. To analyze the percent of each district covered by that school type, select all features in the union output where the School buffer FID value is > -1 and examine the area_percnt values by each district. If you want to analyze the portions of the districts that are not covered by that school type select where the school buffer FID value = -1. It is at least theoretically possible for any given district to be completely in or completely out of any given school type, so the Union tool lets you examine both sets.

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  • Thank you very much. It was really helpful. I already made the exercise and came out well. – a.bueno Dec 1 '14 at 20:25

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