ArcGIS 9.3.1

Basic Concepts

Technology makes life easier.

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Mappers used to have a fancier name.

Part 1

Cartographers: (n)People who make maps.

Landmen: (n)People who like to look at maps.

• ArcGIS is very complex.• Luckily, a landman doesn’t

need to know as much about ArcGIS as a mapper.

• Nevertheless, a modern landman should be comfortable using ArcGIS.

Technophobia

Part 2

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Lumberjack

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Farmer

Landman

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Technology makes life easier.

The secret life of data

Part 3

What is data?• Abstractions, or simplified

descriptions, of reality.

Types of data• Qualitative

– Color, shape• Quantitative

– Number, height, weight, length

Geographical data• Cartesian Coordinates, Lat./Long.,

physical address

Communicating data• The same data can be

expressed in different ways.• The clear communication of

data is as important as the data itself.

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Conclusion:• The “best” way to display data

depends on the end user’s needs.• ArcGIS is a database

management system that allows users to capture, display, and analyze data in multiple ways.

What the heck is a database anyways?

Part 4

Database:• A database is simply a

collection of data.

Simplest database• Flat database

– A table, array, or list• 2-dimensional array

–Rows and columns–Rows contain “records” –Columns contain similar data

about each record• Excel spreadsheet

Database Management System (DBMS):

• A DBMS is a collection of data and routines to perform operations on that data.

Example database operations• Query• Sort• Statistical operations• Joins and relates

– Primary key– Called an FID in ArcGIS

Junk in, junk out• A collection of unorganized,

unrelated data, is practically useless.

Relational Database• A collection of data grouped by

common attributes.– Example: All the oil and gas leases

in Karnes County covering more than 500 net acres.

Multi-table Relational Database

Units

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Leases

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Wells

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Surface Tracts

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Relates

Joins

ArcGIS can display the same data in more than one way

• Maps• Tables• Reports

Lease

Provisions

Thematic Map

Table

Report

Summary:• ArcGIS is a relational database

management system that allows users to capture, display, and analyze data in multiple ways.

• Its strength is in dealing with data related to specific positions in space, called georeferenced data.

• Georeferenced data– Data associated with a specific place on

earth.

Georeferenced data

Part 5

Georeferencing: • The science of showing the relationship

between data and its position on earth.• We accomplish this by using a

coordinate system.– Data + coordinates = georeferenced data

Elements of a coordinate system–Ellipsoid, datum, projection,

units.

Ellipsoid• A good enough model of the earth.• There’s more than one model.• Provides us with a frame of reference in which to

locate features on Earth.

Datum• A set of benchmarks from which

measurements on Earth are made.• Global datum

– NAD 83– WGS 84 (GPS)

• Local datum– NAD 27– Meades Ranch, KS

• Differences in accuracy

Local datums

Not Good Better Even Better

Projection• How to get a 3D Earth onto 2D paper.• Distortions

Units• Feet or meters.

– NAD 27 is typically in feet– Global datums are typically in meters

NAD 27, Texas South Central (4204), feet

Re-projecting layers• If you combine map layers created

with different coordinate systems, they will not line-up.

• ArcGIS re-projects layers on the fly.

Conclusion:• A coordinate system allows us to

relate data to places on Earth using a commonly accepted system of location.

• This georeferenced data can be stored, analyzed, and communicated in a concise, efficient manner.

All this talk about layers

Part 6

ArcMap supports layering

Units

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Leases

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Map layers are a depiction of the multiple tables in a map

Map layers• Vector

– ESRI shapefiles• Geometric shapes: Points, lines,

polygons, polylines• Raster

–Aerial photographs

ESRI shapefiles• 6 different files combine to make a shapefile

Shapefile parts• Geometry (.shp)

–Points, lines, polygons, polylines• Attributes (.dbf)

–Tabular data• Projection (.prj)

–Coordinates

Attributes (.dbf)• The data behind the shapes• Can be exported to a dbase file, which can be opened in Excel.

Raster data• Aerial photos must be georeferenced and in the same projection

as the other map layers

Getting started with ArcGIS

Part 7

ArcGIS is a combination of programs• ArcCatalog

–Manage layers and sources–Create new, empty layers

• ArcMap–View and edit data

Menu barTool bar

File tree

Contents pane

ArcCatalog

Menu barTool bar

Table of Contents

Drawing toolbar

Display area

ArcMap

Maps

Data Frames

Layers

Map Features

Maps contain Data Frames.

Data Frames contain Layers.

Layers contain Map Features.

Each geometric, or vector, map feature in a layer also has a record in the attribute table for that layer.

Primary Key

Lease layer Lease attribute table

Static data– Layers saved to your

desktop

Dynamic data– ArcSDE

ArcSDE• How to provide map data on a multi-user system.• SDE layers live on a server. They can only be edited

by users with editing rights.