Urban planning community | #theplannerlife

+ Reply to thread
Results 1 to 10 of 10

Thread: Industry standard for having a GIS zoning map certified by a surveyor

  1. #1

    Industry standard for having a GIS zoning map certified by a surveyor

    I work with a municipality that has just completed a comprehensive rezoning of it's city.

    We produced a new zoning map using ArcGIS. This essentially involved taking GIS property parcel data maintained by the County property appraiser office and GIS street centerline data, also mantianed by our County, and simply digitizing zoning district boundaries to match these lines.

    The purpose of the map is simply to determine the zoning of each property within the city. It is not the responsibilty of the city to maintain the actual property lotlines, that is undertaken by the County.

    However, in order for the City to officially adopt the zoning map, certain city department heads and the city council would feel more comfortable if the zoning map was officially "certified" by a surveyor. However the surveyor we have begun to work with has never heard of GIS or ESRI and I get the feeling he wants to take a PDF of our GIS zoning map and redraw all of the lines again in AutoCAD and then charge us a bunch of money.

    My questions are this:

    1) Is there a legal requirement for a zoning map to be officially "certified" by a surveyor for it to be legally enforcable by a city government?

    2) If so, seeing as in today's day and age, most zoning maps are created using GIS technologies, is there an official process whereby a Proffesional Surveyor can take the GIS zoning data and simply stamp some sort of seal on it? Are most professional surveyors familiar with this service?

  2. #2
    Cyburbian JimPlans's avatar
    Registered
    Aug 2006
    Location
    Gone to a better place (in my mind)
    Posts
    407
    If the underlying assessor's data is accurate, then you gain nothing from paying a surveyor to essentially double-check your zoning map. If the assessor's office data really is so inaccurate that it can't be depended upon, then your "zoning survey" will turn into an "entire jurisdiction survey", which will be extremely expensive.

    If your jurisdiction is really worried about GIS accuracy, spending money on a one-shot zoning survey seems like a waste. Cecil County, MD just completed a complete revamping of their GIS and survey system, including monumentation densification and height modernization (re-surveying their original 22 control points, adding 97 static points and four NGS‐CORS stations). They are now requiring new development to submit various coordinates for building corners, manholes, parcel lines, etc. are creating a highly accurate cadastral map based on this upgraded system. This is the kind of thing your jurisdiction should spend its money on. Also, Cecil County got lots of grant money to do this, so it didn't cost them much out of their own pocket.

    I worked on a couple of zoning map updates for local jurisdictions in Florida, and they were done just as you descibe. Parcel data from the County assessor was used as a base, and zoning was either applied on a parcel basis or based on road centerlines or parcel boundaries (as in "500 feet from the centerline of X road"). I have never heard of a surveyor needing to stamp a zoning map for accuracy in Florida (or anywhere else). The accuracy comes from the underlying data.

    Is there a reason why your jurisdiction doesn't trust the map data from the assessor's office? Is the assessor's data based on parcel lines that were surveyed, or was it simply digitized from paper maps? What is the accuracy of the assessor's parcels? Is there a reason for your zoning map to be more accurate than the underlying data? Perhaps all that is really needed is language in the zoning regulation that allows for a "fudge factor" in cases where inaccurate basemap data causes issues with demarcating zones.

    As for a surveyor who'se never heard of ESRI or GIS, stay away! Every surveyor should be aware of GIS, and many (most?) use it. I would never hire a surveyor who wanted to give me AutoCAD maps. Even if the AutoCAD data is spatially located and you are given the data files for your own use, I've had too many problems with converting CAD polygons to GIS layers to put myself through it again if I had a choice.

    As for a surveyor "stamping" pre-existing parcel lines, IME the only surveyor that could do that would be the one who created the data in the first place (assuming that the parcel data comes from a survey and not from an intern who digitized old paper maps one summer).

    EDIT: One more thought - zoning maps are often "incorporated by reference" into zoning regulations, which means they do have legal standing, so accuracy is an issue. If the base data is junk, then the zoning map could cause issues down the line. It's not that the City Council et. al are wrong about insisting on accuracy, just that their solution doesn't seem like a good one to me.
    Last edited by JimPlans; 19 Jul 2010 at 1:23 PM. Reason: One more thought

  3. #3
    Cyburbian
    Registered
    Apr 2009
    Location
    Northern Michigan
    Posts
    82
    Quote Originally posted by TonyLoco23 View post
    1) Is there a legal requirement for a zoning map to be officially "certified" by a surveyor for it to be legally enforcable by a city government?

    2) If so, seeing as in today's day and age, most zoning maps are created using GIS technologies, is there an official process whereby a Proffesional Surveyor can take the GIS zoning data and simply stamp some sort of seal on it? Are most professional surveyors familiar with this service?
    1) Only if your state laws require it. The law should state who is responsible for signing off on the official zoning map.

    2) As a surveyor (I'm not), I would not be willing to take work someone else created and certify it as accurate. That would be opening yourself up to some major litigation.

    Some other thoughts:

    Unless you have legal descriptions for each zoning district, the surveyor isn't going to be able to do much besides what you did, anyway. He can scan the original zoning map and then create the amendments, but it all depends on the historical records. A lot of the time the data can be pretty sketchy, unfortunately. Things get lost over decades, and you might not have legals.

    If I understand your methodology correctly, you linked an assessing database to the parcel polygon layer, and then chose symbology based on zoning? Be careful here - it may not take into account parcels that have two districts (i.e. first 3/4 is commercial, back 1/4 is residential). It also depends heavily on the accuracy of the assessing department (for example, lots of times I'll notice a parcel categorized as PUD, where we have no such zoning district).

  4. #4
    Cyburbian Queen B's avatar
    Registered
    Mar 2003
    Location
    "Somewhere in the middle"
    Posts
    3,174
    Are they mad?? I have never heard of such a thing. Our appraisal maps are not survey accurate but I could not understand why that would be necessary. I have never seen zoning maps that accurate or that would need to be.
    It is all a matter of perspective!!!

  5. #5
    Cyburbian ColoGI's avatar
    Registered
    Jul 2009
    Location
    Colo Front Range
    Posts
    2,576
    Quote Originally posted by TonyLoco23 View post

    However, in order for the City to officially adopt the zoning map, certain city department heads and the city council would feel more comfortable if the zoning map was officially "certified" by a surveyor.

    Riiiiiight.

    Sounds like a tactic to say 'no' or delay. Or they have no clue. WTF? Why isn't someone explaining how parcel data is rarely accurate on ground-truthing?? And why didn't the Planning head tell them this?? Sheesh.

  6. #6
    Quote Originally posted by BrianVDB View post
    Be careful here - it may not take into account parcels that have two districts (i.e. first 3/4 is commercial, back 1/4 is residential).
    There are NO parcels in the city that have split zoning, in other words, every parcel is fully covered by a single zoning category. This was one of the things we made sure to clean up during the rezoning process.

  7. #7
    Cyburbian JimPlans's avatar
    Registered
    Aug 2006
    Location
    Gone to a better place (in my mind)
    Posts
    407
    Quote Originally posted by TonyLoco23 View post
    There are NO parcels in the city that have split zoning, in other words, every parcel is fully covered by a single zoning category. This was one of the things we made sure to clean up during the rezoning process.
    Then there is absolutely no reason to have a surveyor check the map. It doesn't matter if the parcel boundaries aren't drawn correctly or aren't located accurately in space. All you need is a two-column table that lists every parcel ID number and its zoning category. You don't even need a "picture" of the zoning in the form of a map.

    Of course, a picture is worth 1,000 words, and mapping your zoning is a useful thing to do. But the map doesn't need to have legal standing (i.e. it doesn't need to be incorporated into the zoning ordinance). Just have the zoning ordinance refer to the zoning-parcel ID correspondence table and put a disclaimer on the map saying that it is only for illustrative purposes and property owners should refer to the official zoning table to discover their property's zoning.

  8. #8
    Quote Originally posted by JimPlans View post
    I worked on a couple of zoning map updates for local jurisdictions in Florida, and they were done just as you descibe. Parcel data from the County assessor was used as a base, and zoning was either applied on a parcel basis or based on road centerlines or parcel boundaries (as in "500 feet from the centerline of X road"). I have never heard of a surveyor needing to stamp a zoning map for accuracy in Florida (or anywhere else). The accuracy comes from the underlying data.
    Jim,

    Thanks very much for your comprehensive reply. I agree with you completely. The hard part will be to persuade the decision makers that all of this is not neccesary. One way to do that would be to get reassurance from other municipalities that have already adopted a GIS based zoning map as their official zoning map.

    Could you provide me with the name of the municipalities that you worked on zoning maps with? That way our planning department could call someone there and get reassurance that adopting a GIS based map as an official zoning map is perfectly fine.

  9. #9
    Cyburbian ColoGI's avatar
    Registered
    Jul 2009
    Location
    Colo Front Range
    Posts
    2,576
    Quote Originally posted by TonyLoco23 View post
    JiOne way to do that would be to get reassurance from other municipalities that have already adopted a GIS based zoning map as their official zoning map.
    Just give them a list of 96% of the incorporated cities in this country.

  10. #10
    Cyburbian JimPlans's avatar
    Registered
    Aug 2006
    Location
    Gone to a better place (in my mind)
    Posts
    407
    Quote Originally posted by TonyLoco23 View post
    Jim,
    Could you provide me with the name of the municipalities that you worked on zoning maps with? That way our planning department could call someone there and get reassurance that adopting a GIS based map as an official zoning map is perfectly fine.
    Instead of contacting municipalities, I think you should contact DCA (assuming you work in Florida as your post suggests). Florida has so many planning statutes and regulations that need to be complied with, I'm amazed that any jurisdiction would purposefully choose to take on more work and expense when making their local plan. All of the statutes and rules I am falimiar with (163.3177, 163.3187, 163.3191, and rules 9J-5 and 9J-11) are silent as to the accuracy of FLU and zoning maps.

    I did find a nice piece of fudge language on a Plant City FLU map created by TPC:

    "ACCURACY: It is intended that the accuracy of the base map comply with U.S. map accuracy standards. However, such accuracy is not guaranteed by the Hillsborough County City-County Planning Commission." This is what they mean by "map accuracy standards."

    But, like I said, contact the Division of Community Planning at DCA. They should be able to give you a definitive answer.

+ Reply to thread

More at Cyburbia

  1. Industry Standard
    Friday Afternoon Club
    Replies: 8
    Last post: 20 Nov 2012, 6:03 PM
  2. Standard zoning map colors
    Design, Space, and Place
    Replies: 33
    Last post: 26 Nov 2009, 12:43 PM
  3. Double standard or not?
    Friday Afternoon Club
    Replies: 18
    Last post: 21 May 2009, 7:37 AM
  4. UD standard in Melbourne
    Design, Space, and Place
    Replies: 2
    Last post: 25 Jun 2008, 7:30 PM
  5. Replies: 1
    Last post: 07 Mar 2000, 4:55 PM