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Visual Resource Inventory. Comparison of Geodatabase to BLM Manual H-8410: Field Sheets Version 1.1 Draft March 2011. Bureau of Land Management – Visual Resource Management System.

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visual resource inventory

Visual Resource Inventory

Comparison of Geodatabase to

BLM Manual H-8410: Field Sheets

Version 1.1 Draft

March 2011

slide2

Bureau of Land Management – Visual Resource Management System

  • BLM’s VRM system provides a way to identify and evaluate scenic values to determine the appropriate levels of management. It also provides a way to analyze potential visual impacts and apply visual design techniques to ensure that surface-disturbing activities are in harmony with their surroundings.
  • The BLM VRM system consists of two stages:
  • Inventory (Visual Resource Inventory)
  • Analysis (Visual Resource Contrast Rating)
  • The inventory stage involves identifying the visual resources of an area and assigning them to inventory classes using BLM’s visual resource inventory process. The process involves rating the visual appeal of a tract of land, measuring public concern for scenic quality, and determining whether the tract of land is visible from travel routes or observation points. (Excerpted from Web Site)

The Bureau has developed a Data Standard that pertains to Visual Resource Inventories. This Data Standard has been physically implemented within a geographic information system (GIS) as an ESRI Geodatabase; which is detailed in the Implementation Guidelines. This document serves to provide an aid in documenting the inventory within the GIS environment, and provides information on cross-walking the information from the field inventory sheets to the Geodatabase. This document does not replace BLM Manual 8410.

slide3

Scenic Quality Evaluation

  • (Excerpts from Manual H-8410-1 - Visual Resource Inventory)

Scenic quality is a measure of the visual appeal of a tract of land. In the visual resource inventory process, public lands are give an A, B, or C rating based on the apparent scenic quality which is determined using seven key factors: landform, vegetation, water, color, adjacent scenery, scarcity, and cultural modifications.

Delineating Scenic Quality Rating Units (SQRU's). The planning area is subdivided into scenic quality rating units for rating purposes. Rating areas are delineated on a basis of: like physiographic characteristics; similar visual patterns, texture, color, variety, etc.; and areas which have similar impacts from man-made modifications.

Evaluating Scenic Quality. Evaluate each SQRU by observing the area from several important viewpoints. Scores should reflect the overall impression of the area. After evaluating all the SQRU's, show the scenic ratings on the scenic quality overlay (see Illustration 7). Record the rating on the Scenic Quality Rating Summary - Bureau Form 8400-5 (see Illustration 4). Bureau Form 8400-1 (see Illustration 3) may be used as a worksheet for completing each scenic quality evaluation. A photographic record should be maintained for the area. Photographs and completed evaluation forms should be filed for future reference.

Scenic Quality Rating Units and Inventory Observation Points shall be represented as geometric features in the GIS, with the related GIS tables being used to document the scores and associated information for each SQRU and IOP. Refer to BLM Manual 8410 for instructions on conducting a visual resource inventory.

slide4

Scenic Quality Evaluation – Example Field Sheet and Summary Sheet

Form 8400-1

Information from these sheets are recorded in the GIS vri_sqru_poly feature class, and the related tables (vri_sqru_factors_tbl and vri_sqru_landscape_tbl)

08/15/1985

08/16/1985

Green River

Green River

Moab

Moab

024

Bob Tumwater, Russ Grimes, Pete Jordon

Bob Tumwater, Russ Grimes, Pete Jordon

Form 8400-5

Deeply cut side canyons with vertical walls leading into flat open valley w/ slow meandering river

Simple forms created by patterns in vegetation

Oval, elongated, and linear

Colorful waterway

Rolling hills, colorless, little veg

Flat, colorless, barren

Water, scenic cliffs, interesting veg

Scenic cliffs

Flat, colorless, barren

Water, riverside veg, colorful cliffs

Good mixture of color, topo & veg

Rugged but otherwise mountainous

Mountainous with good view of N.P.

2

2

2

1

3

2

2

3

2

2

5

0

0

4

0

0

5

0

0

0

0

0

0

0

0

0

0

0

0

0

4

2

2

4

4

2

4

3

2

2

001

002

003

004

005

006

007

008

009

010

3

3

2

4

4

1

4

3

3

1

4

1

1

3

3

1

4

3

2

2

2

3

3

3

4

2

3

3

2

3

20

11

10

19

18

8

22

15

11

10

A

C

C

A

B

C

A

B

C

C

Horizontal and vertical in cliff formations, jagged ridge lines, and meandering river

Irregular, indistinct

Rounded, vertical

Orange and greys dominant, deep blue in settling pond

Dark green in river bottom, grey elsewhere

Light green and grey

Coarse

Medium grain, sparse, and uneven random

Uneven

This SQRU includes the flat and meandering river bed of the Colorado River and the deeply dissected canyons to the north. It differs in landform and vegetation from the surrounding areas. The rock formations and topography are fairly common in the physiographic province but it is uncommon to have a river flowing through this type of landscape. The potash plant which lies in the middle of this area is a major visual intrusion which can be seen from several outlooks and the river.

Comments on 4e – Adjacent scenery: The high scenic rating of “4” was given to this factor because of the high scenic value of the surrounding areas that can be seen from within the SQRU. These scenic areas include Behind-the-Rocks area, Canyonlands country, and the La Sal mountains.

4

2

See explanation above

4

-3

18

5

(-3)

20

slide5

That Portion of the Geodatabase that Applies to

Scenic Quality Rating Units and Inventory Observation Points

FEATURE CLASSESRELATED TABLES

GUIDANCE TABLES

Inventory Observation Points

Scenic Quality Rating Unit: Landscape Character and Element Table

Scenic Quality Rating Unit Polygons (each polygon corresponds to a scenic quality rating unit area, and may be a multi-part feature)

Polygon Arcs (defines polygon boundaries and documents feature level metadata)

Scenic Quality Rating Unit:

Scenic Factor Scores Table

Inventory Observation Point to Associated Scenic Quality Rating Unit Polygon Table (each record in the table is related to each feature class through a one-to-many relationship class)

slide6

Inventory Observation Points GIS Feature Class, Table and Attributes

An Inventory Observation Point (IOP) is either an important viewpoint or is representative of the scenic quality rating unit being evaluated for scenic quality.

Each SQRU will have at least one Inventory Observation Point. Each IOP may be used to evaluate one or more scenic quality rating units.

Within the geodatabase, IOPs are only associated with SQRUs.

Feature class:

vri_iop_pt

Information about the inventory observation point is recorded for each point in the feature class

Attributes:

IOP_ID

ADMIN_ST

ADM_OFC_CD

ADM_UNIT_CD

IOP_NR

IOP_NAME

ELEV_FT

IOP_RPRSNT

IOP_MTHD

IOP_CMMNTS

CREATE_DATE

CREATE_BY

MODIFY_DT

MODIFY_BY

PT_SRC_TYPE

PT_SRC_DESC

ACCURACY_FT

GlobalID

Table:

vri_iop_sqru_tbl

Information about each observation point and scenic quality rating unit pair is recorded in the table

Attributes:

IOP_ID

SQRU_ID

OBSRVR_FT

DT_ANLZ

TM24_ANLZ

EVALUATORS

GlobalID

slide7

Scenic Quality Rating Units GIS Feature Class, Tables and Attributes

Feature class:

vri_sqru_poly

The scenic quality total score and code is recorded for each polygon in the scenic quality rating unit feature class

Attributes:

SQRU_ID

ADMIN_ST

ADM_OFC_CD

ADM_UNIT_CD

SQRU_NR

SQRU_NAME

ADMIN_FO_NAME

SQRU_EVAL

SQRU_ORIG_DT

SQRU_MOD_DT

SQ_TOT_SCR

SQ_CODE

SQ_CODE_TX

SQRU_NRTV1 & 2

SQ_ANLZ_MTHD

GlobalID

Table:

vri_sqru_factors_tbl

The scores and explanatory text for the individual factors of scenic quality are recorded in the factors table

Attributes:

SQRU_ID

SQ_LFORM_SCR

SQ_VEG_SCR

SQ_WATER_SCR

SQ_COLOR_SCR

SQ_ADJCNT_SCR

SQ_SCARC_SCR

SQ_CULT_SCR

SQ_LFORM_TX

SQ_VEG_TX

SQ_WATER_TX

SQ_COLOR_TX

SQ_ADJCNT_TX

SQ_SCARC_TX

SQ_CULT_TX

GlobalID

Table:

vri_sqru_landscape_tbl

The descriptions of the different elements for landscape character are recorded in the landscape table

Attributes:

SQRU_ID

LFORM_FORM

LFORM_LINE

LFORM_COLOR

LFORM_TEXTURE

VEG_FORM

VEG_LINE

VEG_COLOR

VEG_TEXTURE

STRUCT_FORM

STRUCT_LINE

STRUCT_COLOR

STRUCT_TEXTURE

GlobalID

scenic quality field inventory sheet

Cross-Walk Scenic Quality Field Sheet to GIS Feature Class & Tables

Scenic Quality Field Inventory Sheet

GIS Elements & Attributes

Form 8400-1

The GIS attributes are color coded according to the feature class or table:

SQRU_ORIG_DT

ADM_UNIT_CD

ADMIN_FO_NAME

FC vri_sqru_poly

TBL vri_sqru_factors_tbl

TBL vri_sqru_landscape_tbl

SQRU_NR

SQRU_EVAL

LFORM_FORM

VEG_FORM

STRUCT_FORM

  • This implementation contains the following new attributes:
  • SQ_ANLZ_MTHD
    • information on how the scenic quality was conducted from the different IOP’s for the rating unit.
  • SQ_CODE_TX
    • information explaining the assigned code
  • All records for each scenic quality rating unit (polygon) are linked to each other through a primary key:
  • SQRU_ID
    • Concatenated value based on the prefix “SQ” + administrative unit code (ADM_UNIT_CD) + scenic quality rating unit number (SQRU_NR)

LFORM_LINE

VEG_LINE

STRUCT_LINE

VEG_COLOR

STRUCT_COLOR

LFORM_COLOR

LFORM_TEXTURE

VEG_TEXTURE

STRUCT_TEXTURE

SQRU_NRTV1 and

SQRU_NRTV2 (if needed for overflow text)

SQ_LFORM_SCR

SQ_VEG_SCR

SQ_WATER_SCR

SQ_COLOR_SCR

SQ_ADJCNT_SCR

SQ_SCARC_SCR

SQ_CULT_SCR

The value for each attribute corresponds to a score below

SQ_LFORM_TX

SQ_VEG_TX

SQ_WATER_TX

SQ_CODE

SQ_COLOR_TX

SQ_ADJNT_TX

SQ_SCARC_TX

SQ_CULT_TX

SQ_TOT_SCR

slide9

GIS Feature Classes : Scenic Quality & Inventory Observation Points

Example of the feature classes and attribute tables for the Inventory Observation Points and Scenic Quality Rating Units.

Each feature has a unique identifier which is used as a primary key.

Each IOP is related to one or more SQRU

Each SQRU is related to one or more IOP

slide10

GIS Related Tables: Scenic Quality & Inventory Observation Points

vri_iop_pt: IOP_ID (IOP Unique ID) is primary key

Related table to show the IOP to SQRU pairs

vri_sqru_poly: SQRU_ID (SQRU Unique ID) is Primary Key

Related tables to record the Scores for the seven factors of scenic quality, and the landscape characteristics

slide11

Sensitivity Level Analysis

  • (Excerpts from Manual H-8410-1 - Visual Resource Inventory)

Sensitivity levels are a measure of public concern for scenic quality. Public lands are assigned high, medium, or low sensitivity levels by analyzing the various indicators of public concern.

Delineation of Sensitivity Level Rating Units (SLRU's). There is no standard procedure for delineating SLRU's. The boundaries will depend on the factor that is driving the sensitivity consideration.

Documenting Sensitivity Level. For each rating unit, analyze and rate the sensitivity level (as low, moderate, or high) for each of the following factors: Type of Users, Amount of Use, Public Interest, Adjacent Land Uses, Special Areas, and Other Factors.

Determine the overall sensitivity level for each rating unit. This is a process which requires careful analysis of all the factors. Prepare a summary statement with the essential facts and rationale to support the conclusions reached on sensitivity levels. At a minimum, the summary data must be entered on Form 8400-6 (see Illustration 8). Backup information used to evaluate each of the factors should be maintained with the inventory record. Prepare an overlay (see Illustration 9) showing the sensitivity rating units and ratings

Sensitivity Level Rating Units shall be represented as geometric features in the GIS, with the related GIS table being used to document the rating for each sensitivity level factor and its associated explanation. Refer to BLM Manual 8410 for instructions on conducting a visual resource inventory.

slide12

Sensitivity Level Analysis – Example Summary Sheet

Form 8400-6

08/15/1985

Information from this sheet are recorded in the GIS vri_slru_poly feature class, and the related table (vri_slru_ratings_tbl)

Green River

Moab

Bob Tumwater, Russ Grimes, Pete Jordon

001 H HHHH - H within f/m zone of I-70 & U163

002 H L M L H - H visible from river and floatboat users

003 L LLLL - L isolated area with low scenic values

004 H M H M M - H f/m zone for state park entrance road

slide13

Section of the Geodatabase that Applies to Sensitivity Level Rating Units

FEATURE CLASSESRELATED TABLE

GUIDANCE TABLES

Sensitivity Level Rating Units GIS Feature Class, Table and Attributes

Feature class: vri_slru_poly

The sensitivity level overall rating is recorded for each polygon in the sensitivity level rating unit feature class. Each polygon represents one sensitivity level rating unit, and may be a multi-part feature

Attributes:

Table:vri_slru_ratings_tbl

The ratings and explanatory text for the individual factors for sensitivity are recorded in the ratings table

Attributes:

SLRU_ID

SL_USERS_RT

SL_USERS_TX

SL_AREAUSE_RT

SL_AREAUSE_TX SL_PUBLIC_RT

SL_PUBLIC_TX

SL_ADJNT_RT

SL_ADJNT_TX

SL_SPCL_RT

SL_SPCL_TX

SL_OTHR_RT

SL_OTHR_TX

GlobalID

SLRU_ID

ADMIN_ST

ADM_OFC_CD

ADM_UNIT_CD

SLRU_NR

ADMIN_FO_NAME

SLRU_EVAL

SLRU_ORIG_DT

SLRU_MOD_DT

SL_ORVL_RT

SL_ORVL_TX

SLRU_NRTV

GlobalID

sensitivity level rating sheet

Cross-Walk Sensitivity Level Summary Sheet to GIS Feature Class & Table

Sensitivity Level Rating Sheet

GIS Elements & Attributes

Form 8400-6

SLRU_ORIG_DT

The GIS attributes are color coded according to the feature class or table:

ADM_UNIT_CD

ADMIN_FO_NAME

SLRU_EVAL

FC vri_slru_poly

TBL vri_slru_ratings_tbl

SLRU_NR

SL_ORVL_RT

SL_ORVL_TX

  • This implementation contains the following new attributes:
  • SLRU_NRTV
    • Descriptive information about the SLRU as it relates to sensitivity, as well as any additional information on how the area for the SLRU area was determined.
  • All records for each sensitivity level rating unit (polygon) are linked to each other through a primary key:
  • SLRU_ID
    • Concatenated value based on the prefix “SL” + administrative unit code (ADM_UNIT_CD) + sensitivity level rating unit number (SLRU_NR)

SL_OTHR_RT and SL_OTHR_TX

SL_SPCL_RT and SL_SPCL_TX

SL_ADJNT_RT and SL_ADJNT_TX

SL_PUBLIC_RT and SL_PUBLIC_TX

SL_AREAUSE_RT and SL_AREAUSE_TX

SL_USERS_RT and SL_USERS_TX

Note: The attribute pairs, above, are for recording the rating and explanation for each of the sensitivity level factors

slide15

GIS Feature Class & Tables: Sensitivity Level Attribute Values

Example of the feature class, attribute table and related table for the Sensitivity Level Rating Units.

Each feature has a unique identifier which is used as a primary key.

Each polygon in the feature class should have a matching record in the related table.

slide16

Distance Zones

  • (Excerpts from Manual H-8410-1 - Visual Resource Inventory)

Landscapes are subdivided into 3 distanced zones based on relative visibility from travel routes or observation points. The foreground-middleground (fm) zone includes areas seen from highways, rivers, or other viewing locations which are less than 3 to 5 miles away. Seen areas beyond the foreground-middleground zone but usually less than 15 miles away are in the background (bg) zone. Areas not seen as foreground-middleground or background (i.e., hidden from view) are in the seldom-seen (ss) zone.

Mapping Distance Zones. Prepare a distance zone overlay (see Illustration 10). Distance zones should be mapped for all areas. While they are not necessary to determine classes… distance zones can provide valuable data during the RMP process when adjustments to VRM classes are made to resolve resource allocation conflicts.

Coordinating Distance Zones Delineation and Sensitivity Level Analyses. It is recommended that distance zones be delineated before the sensitivity analysis is done. The distance zone delineations provide valuable information that can be very useful in the sensitivity analysis. For example, the foreground-middleground zones are more visible to the public and changes are more noticeable and are more likely to trigger public concern. Also, the boundaries of the distance zones are very useful in helping to establish sensitivity rating units.

Distance Zones shall be represented as geometric features in the GIS. The methodology used to determine the visual distance zone represented by the polygon will be documented (i.e. raster based viewshed analysis, GIS buffer operation, or field observation). Additionally, this implementation allows for the near-foreground distance zone (up to ¼ mile) that is to be used only when inventorying a National Scenic or Historic Trail.

slide17

Distance Zones – Example of Distance Zone Overlay

Illustration 10 - Distance Zone Overlay

Big Flat Squaw Park - West Planning Unit - Bureau of Land Management

slide18

Section of the Geodatabase that Applies to Visual Distance Zones

FEATURE CLASSESRELATED TABLE

GUIDANCE TABLES

Visual Distance Zones GIS Feature Class

Feature class: vri_vdz_poly

The visual distance zone classification is recorded for each polygon in the visual distance zone feature class

Attributes:

  • This implementation contains the following:
  • VDZ_NRTV
    • Descriptive information about the VDZ as it relates to visibility. Comments could include information about the natural or built environment that affects the distance zone, any visual obstructions, or other conditions.
  • VDZ_MTHD
    • Methodology used to determine the visual distance zone presented by the polygon. Examples could include: GIS buffer analysis of roadway, field observation, GIS buffer operation followed by field observation and adjustments, viewshed analysis using DEM/TIN, previously defined distance zones, manual delineation of distance zones and viewsheds, etc.
  • Each visual distance zone polygon has a Unique Identifier (primary key):
  • VDZ_ID
    • Concatenated value based on the prefix “DZ” + administrative unit code (ADM_UNIT_CD) + visual distance zone number (VDZ_NR)

VDZ_ID

ADMIN_ST

ADM_OFC_CD

ADM_UNIT_CD

VDZ_NR

ADMIN_FO_NAME

SLRU_EVAL

SLRU_ORIG_DT

SLRU_MOD_DT

VDZ_CODE

VDZ_MTHD

VDZ_NRTV

GlobalID

slide19

GIS Feature Class & Tables: Distance Zones

Example of the feature class and attribute table for Visual Distance Zones.

The presence of cities and towns, and transportation features such as roads and trails, make all areas shown fall within the foreground-middleground zone for visual distance.

There is no related table for Visual Distance Zones. The Near-Foreground zone is to be used only when conducting an inventory for a National Scenic and Historic Trail.

slide20

Visual Resource Inventory Classes

  • (Excerpts from Manual H-8410-1 - Visual Resource Inventory)

Purposes of Visual Resource Classes. Visual resource classes are categories assigned to public lands which serves two purposes: (1) an inventory tool that portrays the relative value of the visual resources, and (2) a management tool that portrays the visual management objectives. There are four classes (I, II, III, and IV).

Visual Resource Inventory Classes. Visual resource inventory classes are assigned through the inventory process. This is accomplished by combining the 3 overlays for scenic quality, sensitivity levels, and distance zones and using the guidelines shown in the matrix (see Illustration 11) to assign the proper class. The end product is a visual resource inventory class overlay (see Illustration 12). Inventory classes are informational in nature and provide the basis for considering visual values in the RMP process. They do not establish management direction and should not be used as a basis for constraining or limiting surface disturbing activities.

Rehabilitation Areas. Areas in need of rehabilitation from a visual standpoint should be flagged during the inventory process. The level of rehabilitation will be determined through the RMP process by assigning the VRM class approved for that particular area.

Visual Resource Inventory Classes shall be represented as geometric features in the GIS. These features shall be derived from the feature classes for scenic quality, sensitivity levels, and distance zones.

slide21

Determining Visual Resource Inventory Classes

Basis for Determining Visual Resource Inventory Classes

Class I. Class I is assigned to all special areas where the current management situations requires maintaining a natural environment essentially unaltered by man.

Classes II, III, and IV. These classes are assigned based on combinations of scenic quality, sensitivity levels, and distance zones.

* If adjacent area is Class III or lower assign Class III, if higher assign Class IV

slide22

Section of the Geodatabase that Applies to Visual Resource Inventory Classes

FEATURE CLASSESRELATED TABLE

GUIDANCE TABLES

Visual Resource Inventory Classes GIS Feature Class

Feature class: vri_class_poly

The polygons and associated inventory classes for this feature class are derived from the other feature classes for scenic quality, sensitivity and distance.

Attributes:

  • This implementation contains the following:
  • VRI_CLASS_TX
    • Optional text explaining why a specific visual resource inventory class was assigned.
  • VRI_REHAB_IND
    • Yes/No value indicating that the area was identified as needing rehabilitation during the visual resource inventory .
  • VRI_SPCL_IND
    • Yes/No value indicating that the area was identified as possessing unique landscape and/or visual quality characteristics during the visual resource inventory .
  • Each visual resource inventory class polygon has a Unique Identifier (primary key):
  • VRI_AREA_ID
    • Concatenated value based on the prefix “VRI” + administrative unit code (ADM_UNIT_CD) + VRI area number (VRI_AREA_NR)

VRI_AREA_ID

ADMIN_ST

ADM_OFC_CD

ADM_UNIT_CD

VRI_AREA_NR

ADMIN_FO_NAME

VRI_EVAL

VRI_ORIG_DT

VRI_MOD_DT

VRI_CLASS_CODE

VRI_CLASS_TX

BLM_ACRE

SQ_CODE

SL_OVRL_RT

VDZ_CODE

VRI_REHAB_IND

VRI_SPCL_IND

GlobalID

slide23

GIS Feature Class & Tables: Visual Resource Inventory Classes

Example of the feature class and attribute table for the final Visual Resource Inventory Classes.

The polygons depicting the inventory classes are derived through a process where the scenic quality, visual sensitivity and distance zones are combined.

The Visual Resource Inventory Classes are informational in nature, and do not constitute a management class. However, they do serve as a baseline of information from which the affected environment sections of all subsequent NEPA analysis should reference.

slide24

Deriving VRI Classes: Example Using Union, Dissolve & Eliminate Tools

Sensitivity

  • What follows demonstrates only one example of how the final inventory class polygons may be derived. Regardless of methodology, the process should be documented with any interim products maintained.
  • Example using the Union Tool
  • The Union tool is accessed in Arc Toolbox > Analysis Tools > Overlay
  • The union will be performed between SLRU, SQRU and VDZ feature classes with output to an interim file

Scenic Quality

ArcTools Union Tool

slide25

Deriving VRI Classes: Example Using Union, Dissolve & Eliminate Tools

VRI_Union feature class is output of union

  • Output of the Union Tool
  • Geoprocessing results were written to an interim feature class (VRI_Union)
  • All attributes from the three inputs are captured in the output
  • Input polygons are “cracked” and then reassembled so that each new polygon has a unique boundary and SQ, SL and DZ combination that corresponds to the different polygons of the inputs
  • The dissolve tool may then be used to combine adjacent union output polygons that have the same SQ, SL and DZ value

Only the attributes of interest are shown at right

slide26

Deriving VRI Classes: Example Using Union, Dissolve & Eliminate Tools

VRI_Union (input for dissolve)

  • The Dissolve Tool
  • The Dissolve Tool is accessed in Arc Toolbox > Data Management Tools > Generalization
  • The dissolve will be performed against the VRI_Union interim feature class
  • Geoprocessing results were written to an interim feature class (VRI_Union_Dissolve)
  • The SQ_CODE, SL_OVRL_RT, and VDZ_CODE attributes are used in performing the dissolve. There will be no statistics, and single-part (not multi-part) polygons will be created.

Dissolve Tool aggregates features based on specific attributes

ArcTools Dissolve Tool

slide27

Deriving VRI Classes: Example Using Union, Dissolve & Eliminate Tools

VRI_Union_Dissolve feature class is output of dissolve

  • Output of the Dissolve Tool
  • Geoprocessing results were written to an interim feature class (VRI_Union_Dissolve)
  • The SQ_CODE, VDZ_CODE and SL_OVRL_RT attributes are captured in the output
  • Input polygons are aggregated so that adjacent polygons with the same value for SQ, SL and DZ are combined
  • This tool will reduce the number of polygons, but there may still may a large number of very small polygons
  • The small polygons may then be “appended” onto an adjacent larger polygon using the eliminate tool
slide28

Deriving VRI Classes: Example Using Union, Dissolve & Eliminate Tools

VRI_Union_Dissolve (input for eliminate)

  • The EliminateTool
  • The EliminateTool is accessed in Arc Toolbox > Data Management Tools > Generalization
  • The eliminate will be performed against selected features (in this case, acres < 50) found within the VRI_Union_Dissolve interim feature class
  • Geoprocessing results are written to an interim feature class (VRI_Union_Dissolve_ElimLT50Acre)

Selected features are shown above in cyan –

these features are less than 50 acres in size,

and will be merged into an adjacent polygon.

BEFORE

ELIMINATE

AFTER

ELIMINATE

slide29

Deriving VRI Classes: Example Using Union, Dissolve & Eliminate Tools

  • Output of the Process
  • Geoprocessing results were written to an interim feature class (VRI_Union_Dissolve_ElimLT50Acre)
  • All attributes from the three inputs are captured in the output
  • Load the interim data into the vri_class_poly feature class