Someone on another tribe was asking me how to construct cartograms manually. I am copying the post onto this tribe in case someone finds it of use.
You will need graph paper, pencils, erasers, and whatever manual drafting materials you think appropriate.
I will try to simplify the process as much as possible so remember there are several ways to make a cartogram and there are several types of cartograms (contiguous, non-contiguous, single, and two variable, etc.).
1. Consider what is the total area the map will cover
2. Determine what level your enumeration unit will be. This is usually determined by how the data was captured and recorded.
3. Consider the proportion of total that each enumeration has as the size of each enumeration will depend on this.
4. Determine if you map is best served as a contiguous cartogram or non-contiguous cartogram. In other words, do you want to maintain spatial proximity of the total area or do you want to "space" out the enumeration units.
5. Decide as to what degree you can and want to preserve the original shape of the enumeration units.
6. There are several ways to address these issues so you may want to review other atlases, etc. Also, look back too much older cartograms, as there are some beautiful constructions that are no longer being produced thanks to GIS.
7. Now, organize your data into 3 or 5 divisions or ranking classification.
8. From this structure determine a good "counting-unit" for your data. A good way to approach this is to take your largest enumeration unit (that is the one that will be the largest distortion) and take the graph paper and draw that largest unit onto the paper. But be warned you have to visualize how the other units may fit on the page. Once you have done this it will give you a good idea of how many grid squares lie within the border of the enumeration unit. You must also approximate the area within grid squares that are bisected by the border to come up with a total "counting-unit" for that enumeration unit.
9. Now make a chart of your data breaking up the raw data into "counting-units"
10. You can now start drawing your map based on these sizes.
11. I find it easier working with the larger enumerations first and then filling the in-between places with the smaller enumeration units but you have to be able to visualize the data. Most people probably build on each previous constructed enumeration unit to preserve border shapes. This is good too just remember what you imagine your total map to look like.
12. So, you begin to have what looks like a cartogram . . . don't forget to include a key on your map (perhaps a block of the counting unit or several) this should match those data divisions or ranking classification that you previously determined.
13. If there is an enumeration unit where the data equals 0 or is significantly smaller than the other units, I would recommend leaving it out of the cartogram but placing a notation at the bottom of your map. Otherwise, map-readers may think it was an error and that you omitted something that should be there.
14. After you have drawn your cartogram you may want to scan it into a graphics program and then edit it and add text etc. Be sure to scan your key at the same time and ALWAYS include your key in any enlargements or reductions of the map so that it retains accuracy.
I am working on an article that explains combining both manual and computer methods in making cartograms. I will post it whenever I get it done but the paying jobs of course have priority. I hope these short, quick, and dirty instructions are useful and if you have any questions you can send them to michael@cartographic.net.
Cartogram example: www.cartographic.net/graphic..._jpg.htm
You will need graph paper, pencils, erasers, and whatever manual drafting materials you think appropriate.
I will try to simplify the process as much as possible so remember there are several ways to make a cartogram and there are several types of cartograms (contiguous, non-contiguous, single, and two variable, etc.).
1. Consider what is the total area the map will cover
2. Determine what level your enumeration unit will be. This is usually determined by how the data was captured and recorded.
3. Consider the proportion of total that each enumeration has as the size of each enumeration will depend on this.
4. Determine if you map is best served as a contiguous cartogram or non-contiguous cartogram. In other words, do you want to maintain spatial proximity of the total area or do you want to "space" out the enumeration units.
5. Decide as to what degree you can and want to preserve the original shape of the enumeration units.
6. There are several ways to address these issues so you may want to review other atlases, etc. Also, look back too much older cartograms, as there are some beautiful constructions that are no longer being produced thanks to GIS.
7. Now, organize your data into 3 or 5 divisions or ranking classification.
8. From this structure determine a good "counting-unit" for your data. A good way to approach this is to take your largest enumeration unit (that is the one that will be the largest distortion) and take the graph paper and draw that largest unit onto the paper. But be warned you have to visualize how the other units may fit on the page. Once you have done this it will give you a good idea of how many grid squares lie within the border of the enumeration unit. You must also approximate the area within grid squares that are bisected by the border to come up with a total "counting-unit" for that enumeration unit.
9. Now make a chart of your data breaking up the raw data into "counting-units"
10. You can now start drawing your map based on these sizes.
11. I find it easier working with the larger enumerations first and then filling the in-between places with the smaller enumeration units but you have to be able to visualize the data. Most people probably build on each previous constructed enumeration unit to preserve border shapes. This is good too just remember what you imagine your total map to look like.
12. So, you begin to have what looks like a cartogram . . . don't forget to include a key on your map (perhaps a block of the counting unit or several) this should match those data divisions or ranking classification that you previously determined.
13. If there is an enumeration unit where the data equals 0 or is significantly smaller than the other units, I would recommend leaving it out of the cartogram but placing a notation at the bottom of your map. Otherwise, map-readers may think it was an error and that you omitted something that should be there.
14. After you have drawn your cartogram you may want to scan it into a graphics program and then edit it and add text etc. Be sure to scan your key at the same time and ALWAYS include your key in any enlargements or reductions of the map so that it retains accuracy.
I am working on an article that explains combining both manual and computer methods in making cartograms. I will post it whenever I get it done but the paying jobs of course have priority. I hope these short, quick, and dirty instructions are useful and if you have any questions you can send them to michael@cartographic.net.
Cartogram example: www.cartographic.net/graphic..._jpg.htm
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Atlanta
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