ArcView

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Overview

• What is arc view

• What is a shape file

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AV is part of a Family

AV 1AV 1

PCArcInfoPCArcInfo

ArcInfo7ArcInfo7ArcGISArcGIS

AV 2AV 2 AV 3.xAV 3.x

Needed a GUI

?

AV 8AV 8

AE 8AE 8

AI 8AI 8

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Shape Files

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Topology

• “A mathematical procedure for explicitly defining spatial relationships

• In a COVERAGE topology among polys is explicitly stored in the AAT by – storing adjacent poly Ids in LPoly and RPoly

fields in the database. – By storing in the arc-node table the lines

“adjacent” to one another at nodes

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Topology in Shape Files

• Shape files are non-topological – it does not explicitly store topological relationships

• SF are more like drawings

• However, unlike other simple graphic drawing features they– Store polys as one or more ring structures– A ring is a closed non-self intersecting loop

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Why Topology Anyway?

• One reason was to provide a rigorous, automatic way to clean up digitizing errors

• BUILDing topology forces the identification of errors

• Shape files in AV are created and edited in a feature centric way so that slivers, dangles, missing labels, etc. are never created.

• Digitizing in AV is thus a very different experience and one that we are not going to investigate – except if you do it on your own!

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Rings

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3

4 5

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89

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•Walking the ring in clockwise order results in the “inside” poly is always on the right.

In A/V this feature could be 2 polys with two records or 1 poly with 2 parts. Some cmds in A/V can

generate this kind of feature!

Arc 1 Arc 2 Arc 3 Arc 4

Tax parcel 12382

Road right of way

•In the structure a poly can have more than one part!

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Why a different structure?

• Primary advantage of SFs is that the simple data structure allows faster drawing

• A disadvantage is that SFs can be larger than Coverages because shared vertices are not stored twice

• But SFs are not usually 2x the size of a coverage• One reason is that the attribute table of a theme is

a good portion of the size of the file whether it be shape or cover

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Finding adjacent features• Another misunderstanding – AV can find adjacent

polys even though it does not have explicit topology!

selectedSelect by Theme,

Intersect

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Finding adjacent features• Another misunderstanding – AV can find adjacent

polys even though it does not have explicit topology!

selectedSelect by Theme,

Intersect Even

poly

s joi

ned

only

at a

node

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ArcView Terminology

• The Project is the basic AV document. Projects have the extension .apr

• A project holds– Views – the basic window on the graphic

world

– Tables – the attribute data

– Charts – Graphic results of analysis

– Layouts – Map-like graphics

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Views• Views contain the graphic data. A view is made up of:

– A table of Contents (TOC)

– One or more themes of graphic data

– Each theme has a Table “Attributes of xxxxx”

TOC Empty ViewThemes

Active Theme

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Table

• Can be the “attributes of xxxx” or any other data in a database.

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