Data Storage and Processing GIS Topics and Applications

GIS Models Over Time Simple Representation –CAD model Data Analysis –Raster model Data Collection –Vector model Relational and Rules –Object model

Objects GIS Features as Objects is a recent method of representing aspects of the real-world in GIS Example of the shift from specialty data to DBMS that are spatially-aware Non-planar, temporally shifting, topologically linked, rule-based actions

Vector Geometry as Objects Parcels – Planar geometries with attribute information Parcels as objects in a Cadastral “carpet” – Objects with topology rules (“don’t overlap, unless”) – Members of “regional” features (zoning, municipality) – Composed of surveyed parts (COGO, benchmarks) – Keys that link to attribute tables (owner(s), assessments, plans, etc)

Cadastre Example benchmarksurvey (COGO)parcelszones

Attributes as Objects Not only can multiple sets of geospatial features interact with rules, the attributes can be linked with one another, with their own set of rules and actions Ownership record linked to GIS parcel – Search on multiple owners, records – Removal of parcel warns about “orphan” owner Functions that can be performed by GIS analyst can be embedded in the actual database

Manipulating Vector Mode Databases

Common Operations Selection by Attributes or Location Dissolve Append Clip Intersect Union

Select by Attributes Create WHERE clauses that match a subset of the features in a vector dataset. WHERE clauses are a part of Structured Query Language (SQL) Analogous to "Find" in some other software. Match all records where… – "COUNTY" = 'Gloucester' – NOT "TYPE" = 'Wetlands' – "POP2000" >

Select by Location Proximity or overlay based on features in one layer and features in another layer or the same layer. Several methods to compare proximity & overlay – Distance from – Touching (on edge) – Contains or Within – Partial Overlaps – Exact Matches

Dissolve

Dissolve Features InputOutput

Append

Layers to Append Input Layer 1 Input Layer 2 Appended Layers Overlapping Polygons/Polylines are preserved!

Clip

Output Layer Clipped Features Input Layer & Clipping Layer Input Layer Clip Polygon

Intersect

Intersection Where are the Road segments that are in flood prone areas. Select flood prone from Input Layer 1 Intersect roads and flood prone [Layer 2].

Stream No Flood Flood Prone Intersect Features Input Layer 1 Roads Input Layer 2 Panel 1

Stream No Flood Flood Prone Intersect Features Input Layer 1 Input Layer 2 Roads Question: where are the road segments that pass through flood prone areas? Panel 1

Stream No Flood Flood Prone Intersect Features Roads Input Layer 1 Input Layer 2 Select flood prone areas and then intersect Input Layer 1 with Layer 2 Roads. Panel 2

Study Area Flood Prone Intersect Features Output Layer Roads that pass through flood prone areas. Attributes of both layers maintained in table. Length of roads in flood areas becomes attribute Roads Panel 3

Intersection Where are the places that are residential and flood prone. Select flood prone from Input Layer 1 Select residential from Input Layer 2 Intersect

Stream No Flood Flood Prone Intersect Features Input Layer 1 Panel 1

Intersect Features Input Layer 2 Residential Commercial Industry Open space Panel 2

Stream No Flood Flood Prone Intersect Features Input Layer 1 Input Layer 2 Residential Commercial Industry Open space Panel 3

Extent Intersect Features Output Layer Residential & Flood Prone Panel 4

Panel 1 Panel 2 Panel 3Panel 4

Union

Agricultural Land Use Corn Green Beans Tomatoes Wheat Panel 1

Soil Quality Poor Fair Good Excellent Panel 2

Agricultural Land Use Corn Green Beans Tomatoes Wheat Soil Quality Poor Fair Good Excellent Corn &Poor Green Beans & Poor Green Beans & Fair Tomatoes & Fair Tomatoes & Good Wheat & Good Wheat & Excellent Corn & Excellent Panel 3

Let’s See How It Works

Dissolve

Dissolve Operation 1. Right Click 2. Click to select.

1. Click to open menu 2. Click to open Add Field dialog Add Field for Dissolve

Type a name and click OK Name and Type of Field for Dissolve

Table with Code Field Resulting field

Double Click Do the Dissolve

Dissolve Dialog

Dissolve

Click Double Click Append Operation

Append Dialog

Append Two layers before appendOne layer after append

Click Double Click Clip Operation

2 3 1 Clip Dialog

Clipping Roads before clippingRoads after Clipping

Intersection

Intersection Procedure Where are the areas that are residential in land use and flood prone? –Select flood prone areas from flood prone layer –Select residential areas from land use layer –Do intersection

Intersect

Residential

Select by Attributes Dialog Selecting flood prone and water areas

Select by Attributes Dialog Selecting residential areas

Click Double Click Intersection Operation

Intersection Dialog Remember, if you did a selection, then get input features from drop down or drag into dialog from TOC

Intersection Result

Intersection Result

Union

Click Double Click Union Operation

Union Dialog

This map depicts land use patterns for a portion of Washington Township prior to performing the union operation in which land use and flood prone layers were overlain. This map depicts land use patterns for a portion of Washington Township after performing the union operation in which land use and flood prone layers were overlain. Notice that some of the land use polygons have been cut creating new polygons. This occurs in areas in which a polygon from the flood prone layer intersects a land use polygon. The attributes of the new layer enable the analyst to map the coincidence of each land use category with each flood proneness category.