Embed Size (px)
Citation preview
Volusia County, Florida
“Gator Country” 2010 GIS/CAMA Technologies Conference
in
Little Rock, Arkansas
… Data Updated w/2013 info…
“Integration of Subsurface & Surface Land Valuation through GIS Application”
Volusia County-Wide Subsurface Parcels
Subsurface Parcels?
“What is that?”
Understanding “Subsurface Property” requires that you also understand science-
fiction… “Parallel Worlds”
… Let’s so see a “Parallel World” …
“The numbers” that go with “that picture…”
Volusia County ……. 331, 734 Parcels of Property
Subsurface Parcels ….. 1,445
Surface Parcels with Subsurface Rights owned by someone else ….. 12,362
“Intersections” of property lines of Subsurface Parcels with Surface Parcels ….. 14,099 intersections
Why value something under the surface? You can’t see it…
… Many States require valuation of mineral rights.
… Florida’s Supreme Court has ruled that all Real and Tangible Personal Property (including Subsurface Rights), are to be valued annually and placed on County Property Tax Rolls…
… All property is valued at… “Market Value,”.
“Real Property” … The “Rights” flowing from ownership of Real Estate (the ‘sticks and bricks’). The value of all of the “rights” = the value of the property.
“Real Estate” … The physical land and improvements (house and lot). The “rights” owned are “Real Property”
“Subsurface rights” … All “rights” existing below the surface of Real Estate are called Subsurface Rights…. They are also correctly termed “Real Property.”
“Mineral rights” … (Oil, gas, aluminum, coal, kaolin, etc.) all have Real Property rights.
“Surface-to-Subsurface” Relationships
Surface Parcels (are easy)
Have a “One to One” relationship between the legal right owned (physical and visual object to be mapped) and the property’s legal description.
Subsurface Parcels (Contain relationship-challenges)
There is no consistent or predictable relationship between a surface parcel and the subsurface right(s) beneath it. Both “ownership” and “area” relationships exist and either can be complicated…
… Physical ownership lines and ownership percentages of subsurface parcels most often do not match those on the surface.
… In addition, the “area-intersec-relationship” between subsurface and surface parcels must also be maintained over time as “percentage of ownership” and “percentage of subsurface-rights” change.
Percentage of “Sb”-Ownership Example… (percentage ownership in the legal description)
“W”, “X”, and “Y” Subsurface owners, each owning 33.33% of the mineral rights of 100% of a surface parcel.
• These ownership-percentages must be maintained over time… A year later, “Y” sells 50% of his 33.33% to “Z.”
• There are now 4 Subsurface Parcels with ownership:
W=33.33% …of the “100%-area” of the Surface Parcel
X =33.33% …of the “100%-area” of the Surface Parcel
Y =16.67% …of the “100%-area” of the Surface Parcel
Z =16.67% …of the “100%-area” of the Surface Parcel
Percentage of “Sb”-Area Example… (% of “area”, not % of “rights”)
“A”, “B”, “C”, and “D” each own 25% of the mineral rights of 100% of a surface parcel.
Then “B” sells to “E”, 100% of his 25%, to 50% of his surface parcel area ( “B” retains 50% of his subsurface ownership)
There are now 4 Subsurface Parcels with ownership of:
A = 25.0% …of the “100%-area” of the Surface Parcel
B = 25.0% …of the “50%-area” of the Surface Parcel
C = 25.0% …of the “100%-area” of the Surface Parcel
D = 25.0% … of the “100%a-rea” of the Surface Parcel
E = 25.0% … of the 50%-area of the Surface Parcel
Surface/Subsurface Cadastral Relationships
1. One Surface-parcel to One Subsurface-parcel, boundaries matching (a rarity)
2. One Surface-parcel to One Subsurface-parcel, boundaries not matching
3. One Surface-parcel to Many Subsurface-parcels, boundaries matching
4. One Surface-parcel to Many Subsurface-parcels boundaries not matching
5. Many Surface-parcels to One Subsurface-parcels, boundaries matching
6. Many Surface-parcels to One Subsurface-parcel, boundaries not matching
7. Many Surface-parcels to Many Subsurface-parcels, boundaries not matching
…… all of which eventually lead to… “Many-to-Many-3D-Madness”
Volusia’s “Subsurface-GIS/CAMA Project” …5+ Years…
No vendor used, existing staff, working as time permitted, completed this project, which involved the following:
• Physical Identification of all Subsurface Rights Through GIS application (From recorded Deed descriptions)…
• Mapping & interactive linking of the Subsurface Parcel data to the Surface Parcels
• Both of these involved parcel-by-parcel reviewing of the intersections of ownership between the surface parcel(s) and the subsurface parcel(s). This created the physical subsurface area image (like mapping a parcel). However, to value the subsurface parcel, we needed to know its square footage and it’s area percentage to the “related-part” of the surface parcel above. The “intersec-tool” in the GIS created the subsurface area image and performed the square-footage calculations.
How the “intersec” process works
(for us “uninformed-souls”) Surface Parcel “A”
Subsurface Parcel “B”
“Subsurface Parcel AB-Intersec” with Surface Parcel
“Subsurface Parcel B-Intersec” with other-different Surface Parcels
“Pre-Project” Valuation Methodology (rudimentary at best…)
• New “Subsurface Parcels” were created from deed descriptions and hand-drawn on paper maps.
• Valuation was also “by hand” at 10% of Land Value of Surface Parcel at the time of sale.
• There was no “Revaluation procedure” for subsequent-year valuation…
• This created inequities over time and became the reason we began this project.
• There was no consideration of the “area-intersecs” between the subsurface property and the surface property.
• We had GIS in place for a number of years. Until the inequities became evident and we installed a relational CAMA database, this type of surface/subsurface interface methodology was not possible.
“Post-Project” Valuation Methodology Purchasers of Volusia Subsurface rights pay from 10-40% of the value of surface land for the “subsurface rights.” The most prevalent are around 10-15%. We decided to implement the project at 10% of the value of the surface land above it. The value of the Subsurface Parcel will be deducted from the Surface Property above it.
• Prior to GIS technology, simply identifying and mapping the subsurface properties was an impossible task.
• Prior to “relational databases” we would have not been able to “link” subsurface parcels, interactively, to the surface parcels (and/or portions of surface parcels) above them.
• With GIS and a relational database, both are possible, as well as having a viable annual “revaluation” process with a CAMA system.
• A valuation methodology based on the “subsurface minerals” instead of a “% of land value” would still be a “Market Value” appraisal methodology, needing to utilize either (a) “what” is being paid for the land suspected to have minerals …or (b) a geological valuation based on estimated subsurface materials (probably very difficult to obtain).
Subsurface (Sb) Valuation Algorithm
1. Subsurface Value (SbVΣ(v=1-n))
2. Surface Land Value (SLV)
3. Percentage of Surface Land Value to be allocated to Subsurface Parcel (PSLV:Sb v=1-n) … [ for now, set @ 10% ]
4. [Deeded] Subsurface Percentage of Surface Land area ownership (PSb:SOp=1-n) … [ % in legal description ]
5. Percentage of Surface Parcel Area Intersected by Subsurface Parcel Area (PSAIp=1-n) … [ Equals the subsurface “intersec-area” divided by the total surface area ]
Square feet of relative Subsurface Parcel Area divided by Total Surface area
Algorithm… SbVΣ(v=1-n) = (SLV) * (PSb:SLV) * (PSb:SOp=1-n) * (PSAIp=1-n) Where: v = Value (of relative subsurface or surface parcel)
p = Percentage owned and/or intersected, respectively, by either surface or subsurface areas
n = Number of occurrences (varies by parcel)
A simple example…
One-Surface-Parcel to One-Subsurface-Parcel …boundaries matching
The legal descriptions for both surface and subsurface parcels are exactly the same.
$820 = ($10,937) * (10%) * (75%) * (100%)
Valuation Calculations
(% SubSrfc Value) (%Ownrshp) (%Srfc Area Intersctd)
SbVΣ(v=1-n) = (SLV) * (PSb:SLV) * (PSb:SOp=1-n) * (PSAIp=1-n)
“Many to Many-Unmatching”
Each color represents a different Subsurface Parcel
Mineral Rights & Spring Garden Ranch Roads
Number of Surface Parcels: 79
Number of Subsurface Parcels: 8
Number of Subsurface Parcel Intersections: 124
This is “Many-to-Many-3D-Madness”
One “Section” of Land: 660 Acres
Number of Surface Parcels: 135
Number of Subsurf. Parcels: 211
Number of Subsurf. Parcel Intersections: 328
Misty Morgan & Ranchette Road
So, what’s the big deal? All we did was…
• Spend 5 years working… “taking nothing but the researched bare legal descriptions and bringing them into the digital world, parcel by parcel…”
• Then, creating linkages between two different digital polygons that were then linked to two different computer systems, GIS and CAMA…
• This linkage of GIS/CAMA provides needed “Equity” between the valuations of Surface and Subsurface properties that was, heretofore impossible to achieve…
Questions?
Valuation Questions
Morgan Gilreath, Volusia County Property Appraiser
Email: [email protected]
Phone: 386-822-5717
Technical GIS Questions
Rob Miller, GIS Specialist (Rob headed up our project)
Email: [email protected]
Phone: 386-822-5720
