ArcView

1. ArcView

2. Overview • What is arc view • What is ashape file esf Laboratory for Applied GIS

3. ArcView esf Laboratory for Applied GIS

4. AI 8 AE 8 Needed a GUI AV 8 AV 2 AV 3.x AV is part of a Family } ArcInfo7 ArcGIS PCArcInfo ? AV 1 esf Laboratory for Applied GIS

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6. Shape Files Shape Files esf Laboratory for Applied GIS

7. 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 esf Laboratory for Applied GIS

8. 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 esf Laboratory for Applied GIS

9. 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! esf Laboratory for Applied GIS

10. Arc 1 Arc 2 Arc 3 Arc 4 • In the structure a poly can have more than one part! Tax parcel 12382 Road right of way Rings • Walking the ring in clockwise order results in the “inside” poly is always on the right. 8 4 5 9 17 3 16 6 13 15 14 7 10 2 1 11 12 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! esf Laboratory for Applied GIS

11. 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 esf Laboratory for Applied GIS

12. Select by Theme, Intersect Finding adjacent features • Another misunderstanding – AV can find adjacent polys even though it does not have explicit topology! selected esf Laboratory for Applied GIS

13. Select by Theme, Intersect Finding adjacent features • Another misunderstanding – AV can find adjacent polys even though it does not have explicit topology! Even polys joined only at a node selected esf Laboratory for Applied GIS

14. 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 esf Laboratory for Applied GIS

15. Active Theme Themes TOC Empty View 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” esf Laboratory for Applied GIS

16. Table • Can be the “attributes of xxxx” or any other data in a database. esf Laboratory for Applied GIS

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