Ren R 201 Midterm 1

What are the fundamental components that constitute geomatics?

• GIS

• GPS

• Geodesy and Land Surveying

• Cartography

• Hydrography

• Remote sensing

When did CGIS become fully operational?

In the 70s

What are the 4 key benefits of CGIS?

1. Vectorization

2. Map sheets

3. Themes//layers

4. Attributes and locational

What is a geographic information system?

1. People

2. Software

3. Hardware

4. Data

5. Methods and procedures

What are three examples of GIS software packages other than arcGIS?

GRASS

Smallworld GIS

ER mapper

What are the 5 benefits of GIS?

1. Improved decision making

2. Improved communication

3. Geographic management

4. Better recordkeeping

5. Cost saving and efficiency

Give 4 examples of applications of GIS?

Soil mapping

Precision farming

Forest inventory

Microclimate

What are the 5 functional elements of a GIS?

1. Data acquisition

2. Preprocessing

3. Data management

4. Manipulation and analysis

5. Project generation

What is spatial data?

Data that contains positional values, it describes absolute and relative location of geographic features

What is Abstraction in GIS?

The process of explicitly defining and representing real world features on a map

What are the three fundamental geometric primitives in GIS?

Points 

Lines

Polygons

What are the two types of abstraction in GIS?

1. Continuous

2. Discrete

What is a data model?

A conceptual model of the real world

What are layers in GIS?

Collection of geographic data that can be added to a map

What are tiles in GIS?

Division of larger datasets into smaller pieces that make them more manageable

What two data models are used in GIS?

Vector

Raster

What are the differences between vector and raster?

Vector = discrete data with points, lines and polygons

Raster = continuous data with grids and pixels

What are examples of vector and raster?

Vector = water bodies and vegetation areas

Raster = elevation, aerial images and soil types

What are the differences in characteristics for vector vs raster?

Complex data vs simple data

Little storage vs lots of storage

Complex computation vs Simple computation

High resolution vs variable resolution

What is spatial resolution?

The size of grid/ pixel used in analysis: the smallest object that can be discerned

What is raster tellation? Examples?

The partitioning of space into mutually exclusive cells that make up the complete study space; tiling of surfaces using one geometric shape. E.G. Triagles

What are the three different types of map scales?

1. Verbal scale

2. Representative fraction // ratio scale

3. Scale bar // graphic scale

How do you use a map scale to determine real world distances?

Real world width / scale denominator width

What is the difference between a large scale and small scale map?

Large scale = shows smaller areas in more detail; higher RF (smaller denominator)

Small scale = covers large regions so objects and distances are smaller; smaller RF (larger denominator)

What are the data measurement types?

Nominal : denoted with names; forest categories

Ratio : fixed zero point; age, weight

Interval : values on a linear calibrated scale; time of day

Ordinal: determine a relative position ; forest health index

How do the characteristics of variable define the appropriate data measurement type?

Quantitative = interval and ratio

Qualitative = nominal and catagorical

What is the difference between shapefile and geodatabase?

Shapefile: simple format for storing geometric location and attribute information

Geodatabase: a collection of datasets or various types

What are the essential files for shapefile?

.shp=spatial format, .shx=shape index, .dbf=attribute component

What are queries in GIS?

Tools used to search for a select for a subset of features and table record. They are essentially questions posed to a database

What are the three basic methods for searching and querying attribute data?

1. Selection

2. Query by attribute

3. Query by geography

What essential operations does SLQ standardize for regional databases?

The way databases create, retrieve, modify and delete data

How can GIS spatially delineate and quantify all features that satisfy the conditions of a given attribute clause?

Applies SLQ like queries to select, map, and measure spatial features that meet specified conditions

Stat the GIS SlQ operators?

SELECT

FROM

WHERE

ORDER BY

HAVING

What SLQ text syntax and functions are most commonly applied to query and manipulate string attributes wthin a GIS datasets attribute table?

Searching for strings must be encloses in single quotes and is case sensitive

How do SQL relational operators contribute to the attribute-based filtering and selection of features in a GIS database?

Equal to

Less than or equal to 

Greater than

Greater than or equal to

What are some examples of Arithmetic SQL operators in GIS?

Mathematical functions that include addition, subtraction, multiplication and division

What are the types of selection possible when selecting by attributes?

1. New selection

2. Add to current selection

3. Remove from current selection

4. Select subset from current selection

5. Switch the current selection

6. Clear the current selection

What are SQl null values?

Values that haven’t been specified or entered; they are preceded by is and is not

What are the ways to attach non-spatial tabular data to either spatial data or another piece of tabular data?

Join and relate

What is the difference between join and relate?

Join = connects non spatial table to a spatial layer using a common field —> added directly to the attribute table

Relate = links two tables using a shared field but keeps them separate —> creates a temporary connection

What is cardinality?

The nature of the relationship between records in one table to records in another facilitated by a common feild

Describe the types of cardinality?

1. One to one

2. One to many

3. Many to one

4. Many to many

What is a topological overlay?

A geoprocess whereby seperate layers sharing the same spatial extent are merged but in different ways, the overlay function combins not only the spatial features of the dataset but the attribute information as well.

Can you describe the functions and appropriate applications of various tools within extract toolsets?

Clip = extracts input features

Select = extracts features from an input feature class using a select of SQl expression and stores them in an output feature class

Split = splits an input with overlaying features to create a subset of output feature classes

Split by attribute = splits an input dataset by unique attributes

Table select = selects table records by matching an SQL expression and writes them in an output table

What are the vector overlay analysis tools we use?

Erase

Identify

Intersect

Symmetrical difference

Union

Update

What is the erase tool?

It create a feature class by overlaying the input feature with the polygon of the erase feature; only the part falling outside the erase enters the output feature class

What is the identify tool?

It computes a geometric intersection of the input features and identify features; the output class gets the attribute of those identify features

What is the Intersect tool?

It computes a geometric intersection of the input and update features; the feature class returns the area where the two intersect

What is the symmetrical difference tool?

It computes a geometric intersection of the input and update features; the feature class returns where the input and update features do not overlap

What is the union tool?

It computes the geometric union of the input and update features; it returns the combination of the two

What is the update tool?

It computes the geometric intersection of the input and update features; it creates a new output layer containing the update feature

What are some common topological overlay errors?

1. Undershoots; when lines that should touch each other don’t quite touch

2. Overshoots: when lines end beyond where they are supposed to

3. Slivers: where the vertices of two polygons don’t connect

What is spatial analysis?

The process in GIS data of interpreting, exploring and modelling geographic information using GIS software. It uses techniques to reveal patterns, trends and relationships of spatial data

Describe the spatial analysis process?

Start: Define question to be answered →

Acquire data  →

Quality assurance →

Analysis →

Create products →

Distribute data →

Provide a few examples of the spatial analysis approach?

Measuring distances and shapes

Setting routes

Establishing correlations between objects, events and places via their geographical position

Describe the elements used to conduct spatial analysis?

• Data attributes

• Spatial location

• Comparative spatial analysis

Define proximity analysis and its purpose in GIS?

Quantifying and evaluating spatial relationships between features based on their distance or connectivity

What are the different types of proximity analysis?

1. Buffer: creates an area around a feature of interest

2. Thiessen polygon: polygons that divide a plane into regions based on proximity of points in the dataset

3. Near: calculates distances and other proximity information between features in one or more feature classes or layers

4. Spatial query

What does geoprocessing mean?

Using a GIS to manipulate and analyze spatial data?

What are process models in GIS?

Describe or predict environmental phenomena or spatial processes through a series of steps and logical relationships using GIS tools

What are the key components of a process model?

Circles = data

Squares = tools

What are the vector operations that are used to execute process models?

• Define goal

• Base criteria

• Derive data

• Transform

• Weigh and combine

• Locate

What is geodesy?

The science of accurately measuring and understanding the three fundamental properties of earths gravity field, geometry shape and orientation in space

What are graticules?

A grid system formed by latitude and longitude on the globe

What is the difference between longitude and latitude?

Longitude = vertical — up and down

Latitude = horizontal — right to left

What is a geographic coordinate system?

An absolute coordinate system made up of longitude and latitude that enables every location on earth to be specified by a set of numbers and symbols

What is the shape of earth?

Oblate spheroid; flattened at the poles and elongated at the equator

What is a spheroid?

An ellipsoid that approximates the shape of a sphere

What is an ellipsoid?

A squished sphere; predicted by theoretical math, so it doesn’t actually match the bumpy shape of earth

what is a geoid?

The global mean level which accounts for the bumpy shape of earth

What is a datum?

A formal description of the shape of earth along with an anchor point for the coordinate system. It allows for the location of longitude and latitude to be identified on the surface of earth

What is a map projection?

A method by which the curved 3-d surface of earth is represented by X,Y coordinates on a 2-d flat map // screen

Identify and differentiate between the three main classes of map projections?

1. Cylindrical

2. Conica;

3. Planar // azimuthal

what is the difference between tangent and secant?

Tangent = a line which passes through the curve

Secent = a line which intersects two or more points of the curve

Tangent is the most accurate

What are the common projection types of Alberta?

10TM projection

3TM projection

UTM 11 and 12

What are the 5 projection properties and their associated distortions?

1. Area = equivalent

2. Shape = conformational

3. Distance = equidistance

4. Direction = azimuthal

5. Shortest route = gnomonic