[UW-GIS-L] RE: polygon VS attribute table records
lwrogers at u.washington.edu
Mon Jul 7 13:48:21 PDT 2008
I have no idea what the specifics of the problem are, only some possibilities that seem to occur often enough in the work we do. You can learn all about the work of assessors here:
From: Jie Gao [mailto:gaoj at u.washington.edu]
Sent: Monday, July 07, 2008 1:33 PM
To: uw-gis-l at u.washington.edu
Cc: Luke Rogers
Subject: polygon VS attribute table records
Luke, Thank you very much for the clear explanation. may i ask two follow-up questions?
(1) i even discovered situation like: for the Parcel shapefile attribute table (as well as the EXTR_Parcel table) , both of them HAVE a parcel record with major=032105, minor=0000; However, even the Parcel shapefile attribute table has the record (major=032105, minor=0000), selecting that single record (major=032105, minor=0000) won't make any parcel show up in the map. (i definitely zoomed to the correct place, as parcels with major=032105 clustered into a square. however, if only select major=032105, minor=0000, i'd get nothing on the map)
is this the same reason that, the polygon and the attribute table associated with the polygon, are being updated by two different departments. So, even if the attribute table has made the up-to-date correction (adding parcel record major=032105, minor=0000), the "polygon department" does not make the corresponding correction on the map, so the parcel record major=032105, minor=0000 won't show up in the map?
(2) where could i learn the "revaluation notices each winter" you mentioned in the reply? on accessor's website?
many thanks for your help!
Date: Sun, 6 Jul 2008 21:44:01 -0700
From: Luke Rogers <lwrogers at u.washington.edu>
Subject: RE: [UW-GIS-L] how the parcel records are visualized in gis
To: UW - GIS Discussion & Support <uw-gis-l at u.washington.edu>
<BF677F08A5EF984989F1884264A0D51E0136CAB3CF at sdc-mbx-01.exchange.washington.edu>
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While not desirable this is very common. There can be many reasons:
- a particular parcel is not taxed for one reason or another so the assessors don't bother to maintain any attributes with the polygons
- the geometry data and the assessor data were exported on different dates, King County updates their data daily
- the export process and resulting data does not faithfully represent the complex databases that assessors maintain so occasionally things like condos or real property like mobile homes no longer relate to one another
- "segmentations": an big parcel becomes many small ones and the original parcel number is gone. The polygons got updated but the attributes haven't yet, perhaps two different county departments handle the workload
Remember, you are not using the King County assessors data for anything even remotely close to what it was designed for so you just have to take what you can get. The only time that assessor's data has to be right is when they send out the revaluation notices each winter. The rest of the year is spent getting ready for the next years notices...
From: uw-gis-l-bounces at mailman1.u.washington.edu [mailto:uw-gis-l-bounces at mailman1.u.washington.edu] On Behalf Of Jie Gao
Sent: Sunday, July 06, 2008 6:39 PM
To: uw-gis-l at u.washington.edu
Cc: gaoj at u.washington.edu
Subject: [UW-GIS-L] how the parcel records are visualized in gis shape file?
I have a question on how the parcel records are visualized as gis shape file.
more specifically, i encountered following strange situation:
--(1) i download parcel layer (shape file) from Wagda. As usual, this shape file has a dbf table (attribute table) associated to it.
---(2) I also download EXTR_Parcel table from Accessor's website.
-- (3). In theory, tables from step (1) and (2) should be the same.
HOWEVER, i found some records in the EXTR_Parcel table (from accessor's website) do not match the the dbf table associated with the shape file.
Parcel record with major field=620850, minor field=0000 , DOES EXIST in the "EXTR_Parcel" table
However, when i was about to visualize this parcel in GIS (by using the parcel layer i downloaded from Wagda), i found that, the dbf table of the parcel shape file (from Wagda) DOES NOT contain any parcel record with major field=620850 at all !!!
Similar cases are: major field=679130; major field=639165; similar cases are around 120 cases.
Any Ideas on how could this ever happen? -- that is, how come some parcel recordes in EXTR_Parcel table, with explicite major and minor fields, do not have any correponding recordes in the dbf table of the Parcel shape file?? where have those parcels gone on the map then?
any input would be greatly appreciated !!
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