URBDP 422 URBAN AND REGIONAL GEO-SPATIAL ANALYSIS Lecture 3: Building a GeoDatabase; Projections Lab Session: Exercise 3: vector analysis Jan 14, 2014

Objectives of Lecture -Introduce data modeling -Introduce alternative database models -Review elements of geodatabase -Introduce coordinate systems and projection

Data Modeling Conceptual Model: – Users’ view of data Logical Model: – Precise definition of the set of objects of interest to identify the relationships between them including such relationships as “located at”, “owned by”, “is part of”. Physical Model: – Implementation of data model within the framework of relational database technology

Data Modeling

Types of database systems –Flat files –Relational data base –Object-oriented data base

Examples of database systems Flat file(b) Relational (c) object Behavior

Components of a Data File

Overview: Data Base Management Systems (DBMS) Tables in which: –rows: records, observations: information about one occurrence of a feature –columns: fields, attributes, data element, variables one type of information for all features DBMS systems differ according to how they organize these tables.

Data Base Management Systems (DBMS) Flat File Systems all records and fields contained in a single (often very large) rectangular file one field (or a combination) designated as key field –unique identifier for each record used to sort file –records identified by key value can be found quickly

Relational Data Base Systems Characteristics multiple tables (‘files’), each with different record structure tables are related by a common record identifier item (i.e. column variable) present in both tables relations are created on the fly without need to maintain pointers. –relate: temporary connection between two tables –join: permanent merge of two tables into one

The idea of "object-relational" database is to organize information into the sorts of “objects" that people recognize. Instead of "decomposing" each feature in a distinctive list of attributes, features are stored as collections of attributes and behaviors, and can be retrieved or acted upon using a feature name. Object- Relational Data Bases

It enables you to make the features in GIS datasets smarter by endowing them with natural behaviors and relationship among features. It brings a physical model closer to its logical model. The users work with objects of interests such as roads, lakes and transformers. It lets you implement the majority of custom behaviors without writing any code. All of your geographic data can be stored and centrally managed in one database - a uniform repository Object- Relational Data Bases

Comparison of DBMS Approaches

Building a Geodatabase Source: ESRI 2001

Geodatabase and Feature Dataset A geodatabase is a relational database that stores geographic information. Why? To establish and store relationships based on tabular information. A feature dataset is a collection of feature classes that share the same spatial reference frame. Why? To establish and store relationships based on geographic information.

Feature Class A feature class is a collection of geographic objects in tabular format that have the same behavior and the same attributes.

Object Class An object class is a collection of objects in tabular format that have the same behavior and the same attributes.

Relationship A relationship is an association or link between two objects in a database. A relationship can exist between spatial objects (features in feature classes), non-spatial objects (objects in object classes), or between spatial and non-spatial objects.

Relationship Relationship between non-spatial objects Water Quality Data Water Quality Parameters

Coordinate Systems A Coordinate System is a method of locating objects on the earth's surface. Global Plane

Global Coordinate System The most commonly used coordinate system today is the latitude, longitude, and height system.

Latitude and Longitude A latitude, longitude pair specifies the location of any point on the earth’s surface Reference planes are: Equator Prime Meridian

Latitude and Longitude Longitude meridians Prime meridian is zero: Greenwich, U.K. W E Latitude parallels equator is zero 90 N

60 60 N N Pole (90 N) S Pole (90 S) Measuring Latitude o o o o Latitude measures the angular distance from the equator Because the earth is flatter at the poles, tangent must ‘move’ further to change by 1 degree, hence 1 degree of lat. is longer at poles than at the equator.

Measuring Longitude 180 o 135 N Pole 70 West East 70 W 135 E Prime Meridian (0 ) o o o o o Longitude measures the angular distance from the prime meridian.

Latitude and Longitude in distance on the ground Two points on the same north-south line of longitude, and separated by one degree of latitude are 1/360 of the circumference of the Earth (111 km) One minute of latitude corresponds to 1.86 km (one nautical mile) One second of latitude corresponds to about 30 m **But these figures apply only along the Equator. Away from the equator circles of latitude gets shorter and shorter until they vanish altogether at the poles.

…so can we easily, conveniently, sensibly calculate length and area using degrees of longitude and latitude? Not really… All three red areas are 10 degrees on a side. (100 square degrees) All meridians have the same length, but converge at the poles. Lengths of parallels decrease toward the poles (from zero latitude to 90 degrees); their degrees are shorter on the ellipsoid.

The global referencing system is a spherical coordinate system as opposed to a plane or Cartesian coordinate system. The critical distinction is that Cartesian coordinate can be used to measure distances, while the distances between two spherical coordinates is not constant. For example the actual distance between a degree measured at the equator ( km) is much larger than it is near the poles ( km at 60 degrees of latitude). Global vs. Cartesian Coordinate Systems

The process of systematically transforming positions on the Earth's spherical surface to a flat map while maintaining spatial relationships. Map Projection

Map Projection and Distortion Geographic objects have four geometric properties one or all of which can be distorted to a greater or lesser extent depending on the projection used. shape or angle area distance direction We are trying to represent the space on earth on the map space. All projections produce some distortion

Projections types and Property Preserved Equal area projections preserve the area of features Conformal projections preserve the shape of small features (good for presentations), and show local directions (bearings) correctly Equidistant projections preserve distances (scale) to places from one point, or along a one or more lines True direction projections preserve bearings (azimuths) either locally (in which case they are also conformal) or from center of map.

Map Projections - cylindrical projections - conical projections - azimuth projections

The UTM coordinate system is based on the Universal Transverse Mercator Projection. - Earth’s surface is divided into zones 6 degrees of longitude wide. - Zones extend from 80 degrees S to 84 degrees N - Zones are 8 degrees of latitude high. UTM zones

State plane systems were developed in order to provide local reference systems that were tied to a national datum. In the United States, the State Plane System was developed in the 1930s and was based on the North American Datum 1927 (NAD27). State Plane System has been superseded by the NAD-83 System, maps in NAD-27 coordinates (in feet) are still in use. The State Plane System 1983 is based on the North American Datum 1983 (NAD83). NAD 83 coordinates are based on meters. State Plane Coordinates

Map Projections In ArcGIS

Map Projection Overview es/mapproj/mapproj.html es/mapproj/mapproj.html Google Search for: esri understanding map projections pdf Web References