Land Details Bridging the Gap between Assessor Acres and GIS Acres
Assessor Acres and GIS Acres What are Assessor Acres? It is a legally agreed upon approximation of size n n Applies to larger parcels n n Has deep historical roots. n n
• Thomas Jefferson
Thomas Jefferson GIS vs Assessor Acres n n
Assessor Acres • Legally defined area • Fixed area • Absolute precision • Users: Legislature n n Assessors n n Planners n n Citizens
Citizens n n
GIS Acres vs Assessor Acres n n
GIS Acres • Assumes the world is flat • Measurable accuracy in x and y • Area changes to accommodate spatial accuracy • Users: n n
GIS
GIS Common Misconceptions n n
GIS area is more accurate • GIS Area is different n n
Using GIS area would make things easier • Legal areas are fixed • GIS polygons are not fixed size
GIS polygons are not fixed size Analogous to a Linear Reference System (LRS) n n
An LRS route can have user defined length • Events are placed with respect to the defined length. n n
A Parcel can have a user defined area • Sub polygons can be mapped with respect to the defined Area
respect to the defined Area Assessor Acres Applications Current Use Application Areas n n Assessor Easements n n Senior Exemptions n n One Acre Homesites n n Market Value Calculations n n Automated Splits/Merges
Automated Splits/Merges n n
Sample Parcel 1 Acre Homesize n n .55 Acre Natural Gas Easement n n 14.25 Acre Current Use Application n n 15.80 Total Assessor Acres n n
15.277 Total GIS Acres n n Factor: 15.80 / 15.277 = 1.0342
Factor: 15.80 / 15.277 = 1.0342 n n
Land Detail Layer
Sample Parcel Mapping in Assessor Acres Homesite Area: 42122.63 * 1.034212 = 43560
Land Detail ­ Market Value Layer Based on: Slope, Wetlands, Easements, Homesite
Market Value Calculation n n
GIS Acres * Factor * Market Value Type Rate Per Acre
Type Rate Per Acre Current Use Value Layer Based On Soil Types
Current Use Value Calculation n n
GIS Area * Factor * Soil type Rate Per acre
Per acre Appraisers Role Interface between Policy and Public Did you take my wetland, cliff, easement into consideration?
easement into consideration? Appraiser / Public Generalizations n n
Slopes • Includes “Low” or wetland n n
Easements • May not be a recorded easement. n n
Areas • Approximate but set in stone
Approximate but set in stone Easements:
Easements Old School: •2 Sets of books •Maintained Manually •Totals Must Balance •Easements, Wetlands deducted from Flat or Rolling
Mapping Benefits n n
Easements • No longer lost in the database • Can visualize errors, inconsistencies • No longer automatically deducted from high value land n n
Slopes and Soils can use GIS Lidar n n Wetlands Inventory/Model
Wetlands Inventory/Model n n
GIS Mapping Challenges How do you create polygons of a predefined size? n n Real Time Layer Maintenance n n
• In synch with Assessors Database Acreage adjustments n n Easement Add/Drops n n
• In synch with GIS Parcels Layer n n
Parcel edits: Fitting new subdivisions • In synch with Current Use Layer
In synch with Current Use Layer Editing Land Details Place a seed feature: Point, Line, Poly n n Grow the feature to the correct size n n Adjust other features to accommodate the new polygon.
accommodate the new polygon. n n
Homesite Seed
New 1 Acre Homesite
Easement Seed 2.5 Acre Easement
New Easement Homesite moved
Maintenance Parcel Splits and Merges n n Boundary Line Adjustments n n Assessor Acreage Correction n n Add, Drop, edit of easements
Add, Drop, edit of easements n n
Requirements Keep layers in synch with Assessor database n n Keep Assessor database in synch with layers n n Keep it simple
Keep it simple n n
Land Detail Worksheet
Land Detail Worksheet Assessor Database GIS Layer
Split ­ Merge
Merge LandDetail Wizard Summary Spreadsheet / Wizard interface n n Automatically applies most changes to map layers n n Updates GIS Layers n n
• Land Detail • Land Detail Market Value • Current Use Value n n
Updates Assessor’s Database
Updates Assessor’s Database Current Use Mapping based on tree lines, fields n n Acreage based on application n n Applications persist when parcels are split n n One Parcel can have multiple applications n n One Application can include multiple parcels
parcels n n
Conclusions n n
Mapping by area is pretty cool • Presents new ways of viewing information • Simplifies, standardizes, automates many Assessment tasks • Bridges the gap between legal areas and GIS based areas
and GIS based areas