enTaxr[nj] - Tax Maps of New Jersey

New Jersey Geospatial Forum6 June 2014

www.wrwetzel.com/Cartography

Bill Wetzelcarto@wrwetzel.com

Motivation / Trajectory• Wanted convenient access property data for

specific parcels & explore neighborhoods• Browsing difficult, search not forgiving in Open

Public Records. QGIS, ArcGIS don’t scale.• Initial target was Google Earth, KML files

containing property data, awkward user interface• Maps followed from generated shapefiles and

property class, assessment data• Move to Google Maps for intuitive user interface

Results• Intuitive, graphical geospatial index to

property data through Google Maps• Property data for 3,441,254 parcels in 565

towns in NJ• Maps for 21 counties and 565 towns• Error and mismatch logs for 565 towns• Tools for automatic generation of property

data files and maps

Governor’s House

Fundamentals• Municipality, not tile, is basic unit of locality• Fully automatic processing, no manual steps

with gui-based GIS tools• Most work in EPSG:3424 (NAD 83/ NJ)

projection. Convenient to work in feet.• Re-project to EPSG:4326 (WGS 84) for KML

files

Munis Index Map

• All 565 municipalities• Zoom and click on municipality• Curiosities – diagonal line from Readington Township to Little Egg Harbor – must be a story

Counties Index Map• 21 counties• Click on county or text in sidebar

Mercer County Index Map

• Click on municipality• All index maps semi-transparent to show town names on map

Trenton Parcels Index Map

• Zoom in, click on parcel• Parcels index on satellite view• Large municipalities split into sections • Google Maps limitation, 1000 parcels per KML file, about 14 KML files per section• Navigate with Prev/Next

300 Riverview Plaza, Trenton

• Search Box on Parcels Index • Search only meaningful within current municipality• Hide / Show parcels layer• Legend – show legend on sidebar• Parcels Index over satellite view• County / Munis Index over street view

Nearby Area

• Parcels colored by property class• Residential, commercial, industrial muted• Exempt, vacant, farms and others less muted

Property Class Map – Rumson

• All maps to consistent scale• 10 feet /pixel - most• 5 feet / pixel – Monmouth• Space limits of web host

Assessment Map - Rumson

• Colored blue to red• 21 Steps of $150,000• $0.0 to $3,000,000 and up• Exempt – light gray• No data – dark gray• High assessed value of exempt parcels confounded map

•Tax map almost identical, not included here

Property Class Map - Rumson

• Class ID shown in parcel• Same coloring as parcels on Google Maps• Coastline identified and colored• Follows from early interest in identifying waterfront property• Intersection of parcel with buffered coastline• Waterfront parcels no longer marked• Road style of secondary importance

Assessment Map - Rumson

• Assessment shown on edge of parcel if possible• Intent is qualitative heat map

Assessment Map – Monmouth County

• Property Class & Assessment maps for all 21 counties

State Table Index• Alternate to index maps• Thumbnail links to maps• KML files• County table and graphical index

• Graphs are experimental, have rough edges, not discussed further here

County Table Index• Thumbnail links to property class and assessment maps, (property tax maps for Monmouth)• Parcels graphical index• Error log• pams_pin mismatch log

Inputs - Property Data• Mod-IV assessment data• SR-1A sales data

Inputs - GIS Shapefiles• Municipal parcels by county - NJ• County & municipal outlines - NJ• State coastline - NJ• Streets – Open Street Maps• Place names – Open Street Maps• Parcels, coastline, street places all clipped to

municipal outlines

Data Quality• Non-numeric where numeric expected• Non-ASCII characters

– 0xAC in “Ponce, Luis J-Ces*edes” in Rahway– Null character

• Property Class – clean, not validated• Non-Usable Code – oh/zero, spaces, decimal points, some

correctable• Few parcels mislabeled – apparent on maps• Curiosities - One parcel in Wrightstown lies within New Hanover• Winding direction of polygons/holes in shapefiles slightly

inconsistent

Common Errors

Overall, given 3,441,254 parcels, data is remarkably clean

Error Count

Duplicate pams_pin 6981

Invalid recorded date 00-00-0000 289

Undefined numeric non-usable code 103

Incorrect field count in record 56

Non-numeric non-usable code 23

Pams_pin has insufficient parts 18

pams_pin• Critical field – join parcel shapefile with property

data, no data to display if mismatch• Typos – leading zero, extra decimal point• Assessor creativity – non-numeric in block/lot

number: 0904_1_2.B, 0904_189.A_29.A• Inconsistent use of qcode field• Systemic errors – temporal misalignment, lot

renumbering, missing updates, duplication, missing qcodes

pams_pinCorrection Heuristics• Remove qcode – 14,126• Remove leading zero from lot number - 7527• Add leading zero to lot number - 1835

pams_pin Mismatch Rate

• Almost classic 80/20 rule – 16% of towns have 80% of the mismatches

Other Errors

• Log scale used because of large range of error counts. Zero-error-count data points are not shown.• 387 towns have no errors• Jersey City has 6599 errors from duplication

Questions / Plea to Assessors and the GIS Community

• Are lists of errors and mismatches in one place for all municipalities helpful?

• Has anyone done it before? Does anybody care?• If so, how disseminate the lists to assessors or others

for correction?• How validate errors, especially qcode issues?• Assessors – please look at Error Log on the website and

correct the errors, if any, for your town’s property data.

Development Environment

• Linux Mint, Python, JavaScript• Pyshp – shapefile processing• Pyproj – projection translation• Shapely – intersections, buffers• Simplekml – KML file creation• Mapnik – map production• Pandas, numpy, matplotlib – limited use

Future Direction• Move property data from KML file to database• Add generalized search over property data• Add other maps – zoning, hazard (flood and

toxic areas), census data• Add error summaries• Explore GDAL/OGR library• Find market for project