Local vs regional road connections (user search)
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muon2
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« on: December 06, 2015, 05:27:33 PM »
« edited: December 06, 2015, 05:29:37 PM by muon2 »

There are paved roads between the two counties, just not state highways. Don't those count? I thought they did. I believe that they should, even if not for erosity purposes. I don't see the policy reason why not, given the further limitation on flexibility, and potentially forcing chops elsewhere. Yes, the alternative is to chop into Mecklenberg, but then that chops into Charlotte, which is the same as a county chop.

Whole counties have to be regionally connected, ie by means of all-season numbered state/federal highways or ferries. The policy is useful to eliminate weaker local connections across natural barriers like mountains, rivers and deserts and as a proxy for the relative amount of contiguity two counties have. The only exception we've made in the past is for counties that are in the same UCC, where local connections are sufficient. The alternative for flexibility would be to assess additional chop penalties to discourage inter-county linkage based only on local connections.
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muon2
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« Reply #1 on: December 06, 2015, 10:07:09 PM »

There are paved roads between the two counties, just not state highways. Don't those count? I thought they did. I believe that they should, even if not for erosity purposes. I don't see the policy reason why not, given the further limitation on flexibility, and potentially forcing chops elsewhere. Yes, the alternative is to chop into Mecklenberg, but then that chops into Charlotte, which is the same as a county chop.

Whole counties have to be regionally connected, ie by means of all-season numbered state/federal highways or ferries. The policy is useful to eliminate weaker local connections across natural barriers like mountains, rivers and deserts and as a proxy for the relative amount of contiguity two counties have. The only exception we've made in the past is for counties that are in the same UCC, where local connections are sufficient. The alternative for flexibility would be to assess additional chop penalties to discourage inter-county linkage based only on local connections.

I am not sure I agree with that. The compromise, which is reasonable, is no erosity issue without state highway cuts, but no prohibition of links either if paved. It seems a bit too arbitrary, and reduces flexibility, which is needed here to hew to the urban cluster rules. This metric would force a deviation. I think respecting urban clusters is more important myself.

The problem is that the rule doesn't "know" about whether it's being used to protect a UCC pack. The UCC rules should be no more important than other rules (and based on the voting by Atlas members last year, less important). If connectivity is changed to allow local connections and not just regional connections then it affects all counties everywhere, and we can have some unpleasant shapes that simply take advantage of the rule. For sure you can get cross-mountain districts in the West, since that's an area that was used to develop the rule in the first place.

And yes I know about US 52 cutting a corner of Cabarrus. The metric is whether you can go between two county seats on state highways without going into a third county. It is easy to apply. The moment the door is opened to allow a road to go a little bit into another county the metric becomes exceedingly messy as one tries to define how much goes beyond a little.
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muon2
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« Reply #2 on: December 07, 2015, 08:51:33 AM »

No, what makes sense is requiring a paved public road between counties. That is a bright line test. I see no reason to preclude that. A connection is a connection. We will just have to disagree on this one.

I know when we started this exercise in rule building 3 years ago there were cases you wanted to exclude as inadequate connections. I'm thinking specifically of CA, where we didn't think that Ventura should be connected to Kern by Lockwood Valley road, or San Benito to Fresno. I'm not interested in a basic rule changing based on whether a state has built local roads across mountains.

I agree that there is a bright line test that can be used for local connection, and it is used as the rule within counties. I'm leery of using paving as part of the rule, since I've found cases where even state highways aren't paved, and there are rural areas where unpaved local roads are still common and serve as significant connections. From a practical matter as I analyze maps it is sometimes hard to tell what is paved with generally available mapping software. The satellite view helps, but when shoulders are unpaved and the road surface is hard to discern it can still come to an educated guess about the actual road surface.

And I agree that a connection is a connection that is then used for all cases, and yes I mean erosity, too. The Pareto balance doesn't work as well if local connections apply everywhere. I've found changing the scale of connection from county to subcounty to be a huge plus for the rules. Other districting rule systems that I've encountered inevitably have problems as one has districts that cover both large urban areas and rural areas, in part because they don't take scaling into account.
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muon2
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« Reply #3 on: December 07, 2015, 01:40:57 PM »

Are you now ok with the CA county connections that I mentioned? As I said the rule arose in discussion about mountains out west, where such connections were not seen as good policy. The rule was tested in Midwestern states (MI in particular) with counties that had minimal overlaps of boundaries, no highway connections, but nonetheless had local roads.

I ask since it changes the algorithmic nature of finding a neutral map - often in significant ways. For instance it would change the scoring of our MI efforts. It opens up new combinations that can reduce inequality and chops at the cost of erosity, putting them on the Pareto frontier. Going full local also increases erosity for existing plans that took advantage of gaps in the transportation network that are representative of divisions in CoIs, especially those that might not rise to the level of UCCs. Is that change to measured erosity ok in your mind?

It may not be legislation, but I am working on scholarly articles, so details like this matter to me. For instance, I don't really care for the UCC pack rule, but I've accepted the observations of those who are building the maps.
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muon2
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« Reply #4 on: December 07, 2015, 02:54:04 PM »

Ah, but now a connection is not always a connection. Wink

To analyze a plan I transform a map into a network graph of nodes and links, I then partition the graph into subgraphs that correspond to the districts. There are two tests made on the links of the subgraphs: to determine if they are internally connected via links; and to measure the number of severed links. Under my current rule the links to determine that the subgraphs are connected are the same as those that are measured in the cut set that becomes erosity.

You would have two different types of links for the two tasks. From an assessment standpoint the complication is surmountable. From the perspective of developing an algorithm to build maps that challenge is exponentially harder.

It's why I would counter-propose a chop penalty for each disconnected part. It recognizes that one can generally get around regionally disconnected counties by incurring a chop penalty elsewhere (as I did by incurring a pack penalty). That puts it in the same category as the UCC penalties which equate as chops. And it preserves a single definition of link between counties.
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muon2
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« Reply #5 on: December 07, 2015, 03:10:38 PM »


Below is a nice little screen shot from Goggle earth. Isn't that county yellow brick road pretty? Heck it even has a county number (well two of them as it goes in and out of Rowan County, with each county having its own number). If either of us are in the hood, we should take a drive on it, and take some pics. Smiley



I don't think that's the border we were sparring over. That looks like Davidson-Montgomery, not Rowan-Stanly.

To address your LA comment from the other thread, we assume that a county is whole even if not all areas are connected within the county. However, if a county is chopped in such a way that there are no local road connections between the pieces, then there is no link severed there to add to erosity. Ie, you add a chop but can reduce erosity.
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muon2
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« Reply #6 on: December 07, 2015, 03:21:58 PM »

I really did not understand your post. You are the guy who says computers can't be programmed to do it all anyway. There will not be too many county connection issues anyway in most places. It will be a discrete and manageable number. And you can just program into the computer that certain county connections that lack a paved road cause an alert to pop up.

My screen shot was of the wrong two counties. Below is the correct one. There is one yellow road connection, and a couple of white road connections, all paved (except the white road without a number). I am not sure of the difference between the two, other than that wikipedia says that yellow roads are more traveled or bear a road number. But the white roads here have a road number, so what wikipedia says is not precisely accurate.  In any event, the paved roads, be they yellow, or white, are full service roads, with a lane in either direction, divided by a white lane line.  






I haven't disputed that there is a local road connection between those counties. It's not a numbered state or federal highway so it is a local connection, not a regional connection.

What I said about the programming is that it is in a class of tasks that take an amount of time that grows exponentially with the number of units and variables. Thus, one can show that any algorithm needs an exponentially increasing time to exhaustively try every combination to confirm that it has arrived at an optimal solution. Any faster algorithm can't prove that it has the optimal solution such that one could defend it as the best possible plan in court. One can still write algorithms that take less than exponential time and get a near optimal solution. The fewer the variables, the closer to optimal they can reach in a reasonable time.
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muon2
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« Reply #7 on: December 07, 2015, 03:47:59 PM »

This variable however is not the one that will make matters all that much more complex.

In scoring it does not make it much more complex. In searching for an optimal solution it's as complicated as adding another type of population (like BVAP in a section 2 area) to the basic total population. Most automated redistricting systems ignore or fare poorly on VRA compliance in part for that reason.
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muon2
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« Reply #8 on: December 07, 2015, 04:09:24 PM »
« Edited: December 07, 2015, 04:14:32 PM by muon2 »

There are paved roads between the two counties, just not state highways. Don't those count? I thought they did. I believe that they should, even if not for erosity purposes. I don't see the policy reason why not, given the further limitation on flexibility, and potentially forcing chops elsewhere. Yes, the alternative is to chop into Mecklenberg, but then that chops into Charlotte, which is the same as a county chop.

Whole counties have to be regionally connected, ie by means of all-season numbered state/federal highways or ferries. The policy is useful to eliminate weaker local connections across natural barriers like mountains, rivers and deserts and as a proxy for the relative amount of contiguity two counties have. The only exception we've made in the past is for counties that are in the same UCC, where local connections are sufficient. The alternative for flexibility would be to assess additional chop penalties to discourage inter-county linkage based only on local connections.

I am not sure I agree with that. The compromise, which is reasonable, is no erosity issue without state highway cuts, but no prohibition of links either if paved. It seems a bit too arbitrary, and reduces flexibility, which is needed here to hew to the urban cluster rules. This metric would force a deviation. I think respecting urban clusters is more important myself.

The problem is that the rule doesn't "know" about whether it's being used to protect a UCC pack. The UCC rules should be no more important than other rules (and based on the voting by Atlas members last year, less important). If connectivity is changed to allow local connections and not just regional connections then it affects all counties everywhere, and we can have some unpleasant shapes that simply take advantage of the rule. For sure you can get cross-mountain districts in the West, since that's an area that was used to develop the rule in the first place.

And yes I know about US 52 cutting a corner of Cabarrus. The metric is whether you can go between two county seats on state highways without going into a third county. It is easy to apply. The moment the door is opened to allow a road to go a little bit into another county the metric becomes exceedingly messy as one tries to define how much goes beyond a little.
The rule lacks in common sense.



When I spoke in 2010 with redistricting experts who had mapped states in previous cycles they said that one of the easiest ways to gerrymander is to grab populations across a river or forest that you couldn't otherwise conveniently reach, but were contiguous. One even suggested that if he was to only propose only one change to reduce gerrymandering it would be that it had to be possible to reach all parts of a district by car without leaving the district. That sounds like common sense to me.
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muon2
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« Reply #9 on: December 07, 2015, 04:20:33 PM »

This variable however is not the one that will make matters all that much more complex.

In scoring it does not make it much more complex. In searching for an optimal solution it's as complicated as adding another type of population (like BVAP in a section 2 area) to the basic total population. Most automated redistricting systems ignore or fare poorly on VRA compliance in part for that reason.

It's really close to impossible to automate Section 2 issues I would think. At the margins, it is more of an art than a science, and for that matter, at the margins, different courts at present seem to go different ways. I don't think courts even understand it very well. For example, I consider that new FL-05 CD to be very probably illegal as an erose, choppy racial gerrymander with no partisan impact, but nobody seems to mention that but me. The Virginia courts seem to be at sea about how to handle VA-03 appropriately as well.

My point is that it's another variable (local connections), and tracking it is just as difficult as tracking any other variable, even if it is closely related to a variable that is already tracked (regional connections).

Each variable does not add linearly to time, but based on the number of permutations it introduces and that tends to grow exponentially. An optimizing algorithm has to independently monitor all variables and test changes based on the permutations.
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muon2
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« Reply #10 on: December 07, 2015, 04:37:29 PM »

"One even suggested that if he was to only propose only one change to reduce gerrymandering it would be that it had to be possible to reach all parts of a district by car without leaving the district. That sounds like common sense to me."

Sigh. We all agree on that. That's not the point.

jimrtex has consistently held that paths that pass through other districts for short distances as part of a direct connection between two population centers should still count as a connection as long as the counties are otherwise contiguous.

For example one might observe that St Mary and Terrebonne are contiguous parishes and there is a direct route between their county seats. With this view one could make the case that they are connected despite the 3 miles that US 90 passes through Assumption parish.
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muon2
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« Reply #11 on: December 07, 2015, 05:54:14 PM »

In my opinion, you sort of lack standing to complain about complexity. Smiley   And you have not persuaded me, that it is all that much trouble. There are probably in most states, no more than two or three examples of paved roads which are not state highways connecting counties. Perhaps there could be a requirement that the connection be a numbered paved county highway.

I also don't like the idea that for chops, one needs to chop in on a state highway either, which is implied by the rule that you advocate. That might lead to unnecessary chops. I consider avoiding locality chops to be quite important, because when chopped, they are a pain in the ass for local county election boards to administer, because it requires multiple voting rolls, and more variations in the contents of ballots. That is one thing that I have learned since we began this grand, and worthy, enterprise together. Smiley

The rule does favor chops along highways since they can reduce erosity. Even with local connections between counties, there will be a best connection that defines a link. Following that link avoids creating additional erosity. If the chop follows the links from two different counties, erosity is reduced. That favors filling in the corners where counties come together. nb the idea of following links stemmed from a plan of yours for OH years ago that had chops were driven by your artistic eye rather than use strict county integrity.

Obviously one of the big divides in the country is between those states in the east and north that have well defined sub-county jurisdictions, and those in the west and south that do not. I didn't think the rule caused excess locality splits in MI during our lengthy exercise. The aborted exercise in VA a year ago stumbled in part because it lacked the township structure of MI, but still had partial structure in the form of independent cities. That lack of a complete set of subunits created new complexities.
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muon2
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« Reply #12 on: December 07, 2015, 07:24:28 PM »

Erosity is erosty and chops are chops. Two different things. If a using a local county road connection avoids a locality chop, I would like to be able to use it as an option. Having more map options rather than fewer is good thing, not a bad thing.

Regarding traveling chops, rather than just ban them, I think it might be wise to consider allowing them, but if two maps have the same chop count, then the map that avoids traveling chops would be preferred, as superior from a chop standpoint. Again that provides flexibility. My little chop that caused a traveling chop in NC I did not consider a policy problem. So it should be an option, assuming there was no other map with the same chop count that avoided such a traveling chop. And indeed to avoid it, I had to create an extra chop. Minimizing chops should be encouraged, not discouraged.

One query for clarification. I thought we defined traveling chops as those beasts that split two counties between the same two districts. At least that was their meaning when we did the MI exercise. I've used bridge chops to refer to fragments that connect whole counties.

My feeling with both bridge chops and local connections is that since they are used to avoid chops or cluster penalties (which accrue as chops), then if they are permitted they too should come with chop penalties.
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muon2
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« Reply #13 on: December 07, 2015, 11:49:09 PM »

The addition of county roads may work - with some caveats. A cursory check shows there is far less consistency with what a county road means than what a state road means. Not every state numbers their county roads, some use just letter and some use a letter followed by a number. Some counties have roads that are numbered, but not in the sense I think you mean (eg 12 mile road in Kent county MI). Some states have multiple tiers of county roads (MI has three tiers). Some states relegate township roads to a lower class than county roads, but that obviously doesn't happen in states without townships. The problem is that the lowest unit of government gets stuck maintaining all unincorporated public roads, so which are "numbered".

You're from CA, does it make sense for Fresno to connect to San Benito? It would with county road J-1.

Here's my original definition of connection with your proposed change underlined. I haven't tried to define county road yet, but that would need to be part of this.

A political unit can be represented by a node that is the political center of that unit. For a county the node is the county office where the elected officials meet. For a city or town the node is the city or town hall. For a precinct the node is the polling place. Units are connected based on the path that connects their nodes.

Two units are locally connected if there is a continuous path of public roads that allow one to travel between the two nodes without entering any other unit. Local connections can include seasonal public roads. A local connection path can be traced over water without a bridge if there is a publicly available ferry that provides part of the connection. Units smaller than a county must be locally connected within a district.

Two counties are regionally connected if there is a continuous path of numbered county, state or federal highways that allow one to travel between two nodes without entering any other county. If a node is not on a numbered highway, then the connection is measured from the point of the nearest numbered highway to the node. The path may only use roads that are generally available all year. Regularly scheduled year-round ferry service may be included in the path of a regional connection. Counties must be regionally connected to be connected, except that counties within a cluster are connected if they are locally connected.

There is often more than one possible path to connect to nodes. For both local and regional connections the connection between two units is considered to be based on the path that takes the shortest time as determined by generally available mapping software.
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muon2
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« Reply #14 on: December 08, 2015, 07:38:41 AM »
« Edited: December 08, 2015, 07:40:34 AM by muon2 »

The local road culture may need to be state specific as to nomenclature. The main thing is publically maintained two lane pavement. If Fresno to San Benito has such a road, than I don't have a problem with it. You still have an incentive to chop there from an erosity standpoint. But using such roads to avoid county chops I think makes it all worthwhile.

There's a substantial difference between publically maintained roads and "numbered" county roads. I'm not willing to go so far as to include all pubic roads - I've run across subdivision roads that allow one to take a winding path through a residential neighborhood to cross between counties, and I don't think that should count as a regional connection. I also don't want to have to discern which farm roads are paved. As I noted there are numbered state highways in western states that are not paved, and I'm ok with those, since they usually are the main transportation link in their area.

What I'm interested in is a clear definition of county road that doesn't include every local unincorporated road, but is broad enough to cover most states. I don't mind a couple of exceptions, but I don't think that 50 separate definitions is consistent with my generic model. Then I can test it to see how it affects erosity computations. I'm most concerned about the impact on marochopped counties. We went through a lot of effort in Kent county MI to come up wit a model of connections that balanced rural and urban erosities, then we applied it in the Detroit area in a way that made sense. That rural-urban balance is a critical element to the whole concept of erosity.
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muon2
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« Reply #15 on: December 08, 2015, 02:53:51 PM »

When we were engaged in the MI effort we looked specifically at a number of alternate scoring methods for the Kent chop. It was heavily informed by the notion that the local subcounty units not be chopped.  To measure erosity I used local road connections, only state highways, and a hybrid of the two. You and the others supplying Mi maps provided your sense of how the plans should score relative to each other, and then I compared that with my specific scoring method. The result that best matched what the eye desired was a hybrid of local connections within a county and state highway connections between counties. An all local approach like you want in NC was one of the models considered, and the scoring result did not match well with your estimation, or anyone else's, of what appropriate scores should be.

The meaning of locality chops is not clear in a state like NC. There are no statutory electoral units between the county and the precinct, in contrast to states like MI. Electoral divisions in NC and other southern and western states do not generally follow localities for that reason. We can look at the place lines on DRA, but they clearly don't matter to the election authorities when it comes to ballot types. For the VA exercise I generally had to look at other data to get a sense of CoIs that should make up the county subunits.

As I continue to review that status of county roads, I see far less consistencies than I hoped for (and I wasn't expecting much). At this point I'm prone to leave them out of the general rule. I provide for users of the system to amend rules to fit specific state needs, and I think that whether state roads should extend to certain numbered county highways would be a matter for the group using the rules. As I noted in the first paragraph, I would not recommend using local roads for all connections since I can show what that does to the erosity scores from our MI exercise.
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muon2
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« Reply #16 on: December 08, 2015, 04:19:27 PM »

Remind me again of what disaster befell Kent by not requiring state highway connectivity between counties? Perhaps you could repost the map. You just said local road connectivity was OK within a county. So I don't see how the issue can be erosity within a county. Nor do I see how allowing county road connectivity between counties makes the map uglier to the eye per se. In any event, there is an incentive for cuts between counties to be where there are no state highways, since that improves the erosity score.

Of course, it's up to a state to do what it wants. It could allow local highway connections or not, defined as it so chooses, but if it does not allow such local connections, that may well cause more chops as the price. It just seems arbitrary to me. I suspect most legislators would agree, unless allow the Kent example, you can make a good case for it. And unfortunately, I just don't recall the exact details now of that example, to apply again in this context.

For counties with no subunits, you assess the score for the chop in how (other than the erosity score for state highway cuts, with which I agree)?

Perhaps if time permits one of us can search for the thread. It's not a single map, but a set of maps from the proposals put forth by train, jimrtex, you and I. The Kent chop was a common feature in many and simple enough to analyze for erosity in a way that the Detroit area was not.

We independently ranked the set of submitted maps on how we thought they should turn out for erosity. Then I calculated scores using different definitions of connections. The definition that best matched our preconceived expectations was the one that we adopted for the rest of the MI enterprise. That model generated no controversy when applied to the Detroit area and to more rural stretches. There were even maps at that time that went back due to lack of a regional connection, and I did not detect any complaints. I assumed this was because we thought the issue settled after we all put a lot of time in selecting the right balance between regional and local concerns.
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muon2
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« Reply #17 on: December 08, 2015, 06:56:56 PM »

Remind me again of what disaster befell Kent by not requiring state highway connectivity between counties? Perhaps you could repost the map. You just said local road connectivity was OK within a county. So I don't see how the issue can be erosity within a county. Nor do I see how allowing county road connectivity between counties makes the map uglier to the eye per se. In any event, there is an incentive for cuts between counties to be where there are no state highways, since that improves the erosity score.

Of course, it's up to a state to do what it wants. It could allow local highway connections or not, defined as it so chooses, but if it does not allow such local connections, that may well cause more chops as the price. It just seems arbitrary to me. I suspect most legislators would agree, unless allow the Kent example, you can make a good case for it. And unfortunately, I just don't recall the exact details now of that example, to apply again in this context.

For counties with no subunits, you assess the score for the chop in how (other than the erosity score for state highway cuts, with which I agree)?

Perhaps if time permits one of us can search for the thread. It's not a single map, but a set of maps from the proposals put forth by train, jimrtex, you and I. The Kent chop was a common feature in many and simple enough to analyze for erosity in a way that the Detroit area was not.

We independently ranked the set of submitted maps on how we thought they should turn out for erosity. Then I calculated scores using different definitions of connections. The definition that best matched our preconceived expectations was the one that we adopted for the rest of the MI enterprise. That model generated no controversy when applied to the Detroit area and to more rural stretches. There were even maps at that time that went back due to lack of a regional connection, and I did not detect any complaints. I assumed this was because we thought the issue settled after we all put a lot of time in selecting the right balance between regional and local concerns.

Nothing is ever fully settled for the lawyer class. If it were, we would have nothing to do. Tongue

But the bane of model testing for a scientist is shifting the test conditions before a full test is complete. It results in data sets that aren't fit to publish. Tongue
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muon2
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« Reply #18 on: December 08, 2015, 11:33:42 PM »

I'm giving your model a road test as it were. You should thank me, rather than be annoyed. Smiley

Great then we should see how well it performs under the current rules. Wink If it fails to produce a reasonable map in multiple occasions, then it should be modified. One outlier isn't convincing.
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muon2
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« Reply #19 on: December 09, 2015, 08:07:34 AM »

Well said jimrtex, especially the CoI explanation. BTW you need a connection from Washington to Bertie.

Our differing views stem from my strong propensity to avoid paths that cross outside the district. In this case that means paths that go outside the two counties considered for a connection. I think Torie favors this path containment as well, but wouldn't impose the CoI standard of a state highway.

I think that makes four categories of links.

1) Contiguous: the areas share a border greater than a single point.
2) Locally connected: contiguous areas where public roads provide a link without passing through an intervening county.
3) Nearly connected: contiguous areas where there is a convenient state highway linking them, but the path may briefly pass through intervening counties.
4) Regionally connected: contiguous areas where state highways provide a link without passing through an intervening county.

I view the approach as building a region of a whole number of districts by following connections. Then separating regions of more than one district using a minimum number of chops. The FL Senate exercise was a case in point.

Chops modify the connection network.

Chops less than a specified size (5% for CDs) split a single node into two connected nodes. The existing connections are assigned to the respective nodes based on where the primary path associated with the connection crosses the border.

If all chops are treated as above, districts in populous urban areas come out with artificially low erosities regardless of their shape. Chops in these areas need a denser network to assess district shapes and maintain parity with large multicounty rural districts.

So, chops in excess of the specified size are macrochops. Macrochops split the county into a network of nodes based on agreed subunits. Connections are made between these new subunits and from subunits to adjacent counties. Based on the Kent exercise, subunits use local connections within a county and regional connections to adjacent counties. The limitation of cross-county connections to regional links for subunits was an important result from the work in MI to maintain the rural-urban balance for erosity.
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« Reply #20 on: December 09, 2015, 02:12:39 PM »

I've been doing some research on the NC road system. They claim to have the greatest number of road miles in the US. That's in large part because there are no county roads in NC. Any road not maintained by a municipality is maintained by the state. Most of those roads are called secondary roads (SR) and some have numbers used for DOT purposes, but they aren't always marked and they aren't intended for navigation. They move them up to primary state roads when they are of regional significance.

For instance the roads Torie initially posted on the Montgomery-Davidson border are SR's. Mapquest doesn't show those numbers at all and Bing maps only show a number on the Montgomery side (Blaine Rd  NC - 1161) but not on the Davidson side (Badin Lake Rd). Based on the NCDOT guidance I would classify them as local roads rather than numbered highways.

OTOH, there are lots of legitimate numbered state highways that aren't "highways". I'm going through all the yellow links on jimrtex's map to see how I would classify them. I'll post that soon.
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muon2
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« Reply #21 on: December 09, 2015, 03:00:52 PM »

"OTOH, there are lots of legitimate numbered state highways that aren't "highways"." 

What does that mean?

It means they didn't show up on jimrtex's map as blue links, but I would include them.



In this map I have revisited the yellow links on jimrtex's map.

Blue are regional connections based on continuous state highways between two county seats that don't enter a third county. The dark blue links were those not identified previously, but meet my criteria.

Green is a all year ferry connection that meets the criteria for a regional connection.

Yellow are local connections that rely on local roads to establish a path between counties.

Orange are near connections based on state highways where the highway path cuts a short distance through a third county, such as at a corner.

Gold are connections equivalent to both yellow and orange.

Pink are contiguous counties without a connection.

Red squares are places with point contiguity.
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muon2
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« Reply #22 on: December 09, 2015, 06:37:09 PM »

Here is an illustration on how I view the interplay between (macro)chops and connections. I start with the county connections, like the blue lines in the state map below.



When a macrochop (>5% of a CD) occurs, then the single node of the county is replaced by a network of nodes associated with the county subunits. Mecklenburg is a good example to use, since it has to be macrochopped in any plan. NC doesn't have functioning townships in the way MI does, and unincorporated areas are annexed to the nearby towns when the population gets large enough. So I created subunits for the 6 independent towns and the 6 planning areas for Charlotte from the city website. All of the precincts are assigned to one of these 12 subunits as nearly as practicable. The subunits are shaded on the map below.

Each of these subareas is connected other subareas within the county if they are locally connected as shown by the gold links. The subareas are then connected to the adjacent county nodes as either regional connections (blue), local connections (gold), or contiguous but disconnected (pink). These are all shown on the map below as well.

At this point I can proceed as if this was the new state map with a bunch of extra counties (the subunits) where Mecklenburg was. My rules currently treat the gold links inside Mecklenburg as valid connections, but only the blue links that cross county lines as connections. Erosity is calculated the usual way by evaluating which links are severed.



Note that macrochops create new links both within the county and to adjacent counties. If this weren't a macrochop, I would only replace the county with one subunit for each chop fragment. The only new links would be the internal connections between fragments.

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muon2
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« Reply #23 on: December 10, 2015, 11:21:16 PM »
« Edited: December 10, 2015, 11:45:45 PM by muon2 »

I've had a long busy day.

I'm not sure what the beef is about NC 209 connecting Haywood and Madison. I put Waynesville and Hot Springs into Mapquest, Bing and Google Maps as end points. All returned NC 209 as the preferred route with the shortest time and the route crosses into no other counties. From there I go down US-25 to Marshall. If I place Marshall as the end point, NC 209 still comes up on Bing as one of the choices, even if not the shortest (1 h 18 min vs 1 h 1 min which is 28% longer). I try to take a consistent approach to connections, without a subjective judgement about their nature in terms of efficiency.

I use Mapquest and Bing as cross checks on each other since both have renderings of the county lines as I magnify the scale. Google Maps which does not show county lines. Bing is also the mapping for DRA so there is some consistency in using Bing, but the DRA version uses a 2010 Navteq file.

Mapquest and Bing both render the county lines at Little Pisgah Mt as a four-corner junction. Bing kept it as four-corner to as small a scale as I wanted. That led me to place a red square there.
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muon2
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« Reply #24 on: December 11, 2015, 09:14:33 AM »
« Edited: December 11, 2015, 09:46:06 AM by muon2 »

The Henderson-Rutherford connection is based on Hendersonville to Rutherfordton (those are easy seats to keep track of Smiley ). Bing lists three choices with I-26/NC-108 as the best at 37.3 mi and 49 min (light traffic), that's one that goes through Polk. The third choice follows US 64 at 39.0 mi and 75 min without going through Polk. There's no question that US 64 is a main highway, and it doesn't bypass any significant population center. 64 is one of two US routes that cross the ridge on the eastern border of Henderson, but because it was not improved to a limited access highway it takes 50% longer.

I don't have an objective threshold to say when one route is too much longer than another, and I'm more concerned about keeping paths within a single district, so I count it. That second point is why I disliked VA-3 so much. It relied on a number of contiguous water crossings without a path from one end to the other that stayed in the district. I'm willing to go out of my way to insure a complete path.


Edit: Thanks for the info on Little Pisgah. I wonder why the GIS data doesn't show a 150 m border. There are other places where I've seen borders that short.
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