CHP Office Map

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norcalscan

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This is great work, thank you! Can I ask where you get some of the rural boundary data? Are you seeing official maps, or officer word-of-mouth, or is it more of a logical guess based on terrain and office distance? There's a couple boundaries on Northern Red that sort of surprised me a bit and just wondering.
 

ka6sqg

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This is great work, thank you! Can I ask where you get some of the rural boundary data? Are you seeing official maps, or officer word-of-mouth, or is it more of a logical guess based on terrain and office distance? There's a couple boundaries on Northern Red that sort of surprised me a bit and just wondering.
I made this by processing a couple recent years of public incident data. The polygons are where a particular office is almost certainly the agency taking the incident report, after scrubbing out a bunch of geocoding errors and eliminating a fair percentage of stray cross-boundary data. If you have a particular location you think needs adjustment, let me know, and I'll go back and look at the (megabytes of) raw data.
 

ka6sqg

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The most interesting data to me is how much of SF north of Golden Gate Park is handled by Marin units. But there's also some other unexpected things if you look for them.

Because of how this was generated, the accuracy of the exact boundary increases as you get closer to freeways, such that right on a freeway it is probably right within feet, but out on rural roads might be a mile or two.
 

ka6sqg

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What app do you use to open a .kml file?
You can open in Google Earth on desktop or mobile app, or you can import it to Google Maps or other mapping tools fairly easily.

I have it imported to my mobile Google Maps so that I can see where my car is in relation to the boundaries.
 

norcalscan

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The polygons are where a particular office is almost certainly the agency taking the incident report
Duh - didn't even think of that. Yeah I'll let you know if I find any corrections up in the rural NorCal. I'm eyeballing 36E near Lassen, the eastern boundary of Red before Amber was a lot further west than I expected. My unofficial line has always been Morgan Summit. I'll keep a closer eye on the responding office for any calls up there.
 

Paysonscanner

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I've touched up the map I was working on a few weeks ago, and it is available for all at CHP KML

Corrections welcome.
I noticed that the boundary line for the western Sierra Nevada area offices is not shown on the crest of the range. I don't think this is accurate. For example the dividing line between the Bridgeport area office and the Sonora area office is located east of the crest along a straight line that does not follow the crest at all. CHP tries to follow county lines, with at least one area office per county, with a couple of exceptions. Sometimes boundaries between the offices are on other lines due to access issues in the field. Many county lines don't follow topography and the CHP tries to follow it when drawing lines.

I don't follow why the lines are weird in the area of Mojave, some areas have no frequency color at all. There are little peninsulas of frequency color instead of a clean line to the boundary of the area offices. This does not seem to be the actual case on official CHP maps. There are other areas in the state with islands of non frequency color as well and I don't understand why. Do these imply there is no radio coverage in those places?

You should remove all land within Yosemite and Sequoia-Kings Canyon National Parks showing any frequency coverage. These are exclusive federal jurisdictions where state and local governments have no jurisdiction. So the CHP does not include these areas on their maps.

When this and some other issues are cleaned up this will be a very useful tool, especially because it loaded onto my Google Earth and I can bring it up when I need it.
 

2k1typeSH

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Good map! Just a quick suggestion - 465 Modesto (Yellow) covers all of Stanislaus County. The current map shows western Stanislaus County being covered by 390 Dublin (Khaki) and 340 San Jose (Ruby).

I noticed that the boundary line for the western Sierra Nevada area offices is not shown on the crest of the range. I don't think this is accurate. For example the dividing line between the Bridgeport area office and the Sonora area office is located east of the crest along a straight line that does not follow the crest at all. CHP tries to follow county lines, with at least one area office per county, with a couple of exceptions. Sometimes boundaries between the offices are on other lines due to access issues in the field. Many county lines don't follow topography and the CHP tries to follow it when drawing lines.
According to the CHP's website "The Sonora Area has traffic safety responsibilities for Tuolumne County (excluding Yosemite National Park) and a small portion of northern Mariposa County." Furthermore, "The Bridgeport Area has primary traffic enforcement responsibilities for the majority of unincorporated Mono County including approximately 110 miles of US Highway 395 starting at the California Nevada State line traveling south to “Tom’s Place” (just south of Mammoth Lakes, California)."

Therefore, the map can show the Sonora office boundaries following the boundaries for Tuolumne County.

In addition to utilizing CHP's CAD, you can use their "find an office" website to look up specific information for each office throughout the state. Some offices include the geographic boundaries they are responsible for.
 

ka6sqg

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Good map! Just a quick suggestion - 465 Modesto (Yellow) covers all of Stanislaus County. The current map shows western Stanislaus County being covered by 390 Dublin (Khaki) and 340 San Jose (Ruby).
That's an artifact of how the map was generated. It may be that on paper 465 covers all of Stanislaus, but the incident data shows otherwise. I can adjust the map for places where there's supporting information that I can use for the actual boundary and I've added this to my list of boundaries to review.

According to the CHP's website "The Sonora Area has traffic safety responsibilities for Tuolumne County (excluding Yosemite National Park) and a small portion of northern Mariposa County." Furthermore, "The Bridgeport Area has primary traffic enforcement responsibilities for the majority of unincorporated Mono County including approximately 110 miles of US Highway 395 starting at the California Nevada State line traveling south to “Tom’s Place” (just south of Mammoth Lakes, California)."

Therefore, the map can show the Sonora office boundaries following the boundaries for Tuolumne County.
Well... the map can show the Sonora office following the boundaries for Tuolumne *and* the small portion of Mariposa County... and my data shows what that small portion of Mariposa looks like in actual day to day operations. If I could get a source of exactly what that small portion is, I could adjust.

In addition to utilizing CHP's CAD, you can use their "find an office" website to look up specific information for each office throughout the state. Some offices include the geographic boundaries they are responsible for.
There's over 100 offices. It isn't practical to read the textual description of each and convert it to boundaries, and the vast majority do not in fact include that information. Plus, as I've seen in the source data, what they claim to cover and where the units actually respond don't always correspond.
 
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ka6sqg

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I noticed that the boundary line for the western Sierra Nevada area offices is not shown on the crest of the range. I don't think this is accurate. For example the dividing line between the Bridgeport area office and the Sonora area office is located east of the crest along a straight line that does not follow the crest at all. CHP tries to follow county lines, with at least one area office per county, with a couple of exceptions. Sometimes boundaries between the offices are on other lines due to access issues in the field. Many county lines don't follow topography and the CHP tries to follow it when drawing lines.
It is possible that these look this way because of the relative rarity of incident data geocoded in these area which means that the boundary is "fuzzy" when generated from the data. As I noted above, the detail level is very accurate where there's busy freeways, and can be off by a few miles when it isn't.

In particular, where incident data is very rare, the boundary is shown as the midpoint between incidents investigated by different offices.

I don't follow why the lines are weird in the area of Mojave, some areas have no frequency color at all. There are little peninsulas of frequency color instead of a clean line to the boundary of the area offices. This does not seem to be the actual case on official CHP maps. There are other areas in the state with islands of non frequency color as well and I don't understand why. Do these imply there is no radio coverage in those places?

The areas of no color occur where there's very little incident data, and what data there is was in conflict (e.g., there might be a small patch where two or more offices generated incidents the overlap back and forth such that it isn't clear whose area it is)... this causes small islands of other offices within the dataset, and when those islands were small I deleted them manually, leaving a color-less area.

The little peninsulas are formed for a similar reason, when there's multiple incidents that reach out beyond a natural boundary from one office, and then another office clearly covers all around that. Sometimes that's due to where roads are connected in mountainous areas.


You should remove all land within Yosemite and Sequoia-Kings Canyon National Parks showing any frequency coverage. These are exclusive federal jurisdictions where state and local governments have no jurisdiction. So the CHP does not include these areas on their maps.
Good point... what other areas of the state are also federal-only? Vandenberg AFB might be an example?
 
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Paysonscanner

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It is possible that these look this way because of the relative rarity of incident data geocoded in these area which means that the boundary is "fuzzy" when generated from the data. As I noted above, the detail level is very accurate where there's busy freeways, and can be off by a few miles when it isn't.

In particular, where incident data is very rare, the boundary is shown as the midpoint between incidents investigated by different offices.




The areas of no color occur where there's very little incident data, and what data there is was in conflict (e.g., there might be a small patch where two or more offices generated incidents the overlap back and forth such that it isn't clear whose area it is)... this causes small islands of other offices within the dataset, and when those islands were small I deleted them manually, leaving a color-less area.

The little peninsulas are formed for a similar reason, when there's multiple incidents that reach out beyond a natural boundary from one office, and then another office clearly covers all around that. Sometimes that's due to where roads are connected in mountainous areas.




Good point... what other areas of the state are also federal-only? Vandenberg AFB might be an example?
I'm not an expert on the military. I think most military bases that have more than a few acres and are in the hundreds of acres, which are closed to the public are areas of exclusive federal jurisdiction. Vandenburg and Camp Pendleton come to mind as exclusive jurisdictions. Others I can think of would include Edwards (USAF), 29 Palms (USMC), China Lake (USN), and Lemore (USN). I'm not sure for the smaller facilities like the Los Angeles Air Force Base, which is pretty small. Even then I would think it would have an exclusive jurisdiction since it is closed to the public. Small facilities such as the Navy's language school in Monterey are not closed to the public and probably concurrent or maybe proprietary jurisdictions where the federal government is a property owner only and don't usurp any local authority. This is all from conversations with NPS and USFS employees when we lived in California. Hubby, being a civil engineer for a county had to know this stuff as well as there were Bureau of Reclamation reservoirs, national forest land, state parks and NPS boundaries he dealt with.

My late husband was trying to find a list of national parks and their jurisdiction type. The older, larger parks are exclusive jurisdictions and those that are not are usually a concurrent jurisdiction where the state and county have jurisdiction within the park and the NPS has full jurisdiction as well. According to a friends we had in California, who worked for the NPS, most of the time the NPS provides all services in concurrent parks as they think they have responsibility for drawing so many visitors into an area so they will take care of the workload as opposed to creating a burden on local agencies. Surprisingly Grand Canyon National Park is an example of this as it is concurrent, but I've never seen any AZ DPS or Coconino County Sheriff's deputies in that park. I don't think Lassen Volcanic, Pt. Reyes, Joshua Tree, Mojave and others are exclusive. My late Hubby talked to some rangers at Death Valley who said that park is concurrent. He was working on finding a list when he got sick so it never got done.

Rest assured that the area offices south of Lake Tahoe are on the crest, there isn't any fuzziness there. The only exception is the road to Devils Postpile National Monument, which is accessed by vehicle from Mono County only so it is in the Bridgeport Area Office. The Sierra Crest is not easy to access for any of the offices in the central and south Sierra Nevada, at the ends of their jurisdiction so the chances of a Sonora Area Office officer to respond to an accident east of Sonora Pass are very low. I seem to remember that in the cases of callers not knowing where they are, if a westside unit finds the wreck/etc. east of the crest they wait for a unit from the respective area office to arrive and take care of the investigation. Somewhere in my Hubby's notebooks are some maps of some Sierra Nevada area office jurisdictions which show the crest as the boundaries. I picked up a pretty tough respiratory infection during Christmas and am down at my younger brother's house in Phoenix and the books are in Payson at my parent's house so I can't scan and post them right now.
 

2k1typeSH

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An additional resource, directly from the CHP’s website:
79224
Increase the transparency of this map and overlay it on a map of the state with county lines. You will then have all the exact boundaries. Just an idea.
 
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