GIS Exam 1

How can you typically recognize a coverage that you download from the web?

(.e00 files)

What are key Geographic Information Technologies?

- Global Positioning System - Remote Sensing - Geographic Information System

What are the ways we can get GIS data or get data into GIS?

- field collection - earth observations

What are the components that make up a Geographic Information System?

- people - software - data - procedures - hardware

What are the three common file formats?

1. Coverages (older format) (.e00 files) 2. Shapefiles (composed of multiple files) 3. Geodatabases (modern way) (personal, file, or ArcSDE)

What are the Rules, Laws, Strong Recommendations, for dealing with Data in ArcGIS?

1. Download the data and figure out what the coordinate systems are (typically in the metadata) 2. Define the current coordinate systems of each of the layers (tell arcGIS what the coordinate system is) 3. Transform or reproject each of the layers to one common coordinate system 4. Start doing GIS

How many State Plane zones do we have (NAD83)?

120

What UTM zone are we in?

17N

What are common datum/ellipsoid pairs?

3 Most common for North America NAD27 (North American Datum of 1927) (Clark 1866 ellipsoid) NAD83 (North American Datum of 1983) (GRS 1980 ellipsoid) WGS84 (World Geodetic System of 1984) used for GPS • (GRS 1980 ellipsoid)

attribute table (or database)

A set of data tables in digital form describing what is found at the positions (locations, areas, along lines etc..) in the spatial database. • Attribute data is tied to spatial data

How do we manage metadata in ArcGIS?

ARC catalog

What are the characteristics of the Raster Data Structure?

Bunch of equally sized squares; resolution = the size of one side of the box • Ex: used for digital elevation model -- each color corresponds to a different value • Used to make slope maps and aspect maps • Raster images store everything as numbers

What is a continuous raster data layer and what types of data are represented in a discrete raster?

Continuous Raster - raster in which cell values vary continuously to form a surface. In a continuous raster, the phenomena represented have no clear boundaries. Values exist on a scale relative to each other.​​ Data Types: land cover map, elevation models

What is a small scale map?

Covers large area with less detail

What is the difference between project and define projection in ArcMap

Define Projection is what you use when the data has no defined coordinate system (unknown spatial reference). It only changes the metadata it doesnt change the projection Project is what you use to portray a curved surface of the earth on a flat surface. It changes the projected coordinate system of your data to another coordinate system

what is a DLG? (what GIS structure is it typically in?)

Digital line graphs • Vector • Come in seperate data layers • Has an attribute table because it is actual spatial data • Good for historical data

What is a discrete raster data layer and what types of data are represented in a discrete raster?

Discrete Raster - raster that typically represents phenomena that have clear boundaries with attributes that are descriptions, classes, or categories.​ Data Types: Buildings, roads and parcels of land

What can happen if you have a two GIS layers in the same coordinate system, EXCEPT each layer has a different datum? Do they line up? (datum shift)

GIS data layers use all of these different datum systems. It is impossible to overlay two GIS data sets with different datum systems as there can be errors of up to 10's to 100's of meters.

What are the two general types of coordinate systems?

Geographic Coordinate System - 3D spherical surface to define locations on the earth (latitude and longitude) Projected Coordinate System - Defined on a flat 2D surface (take the globe and flatten it)

What does GIS stand for?

Geographic Information System

What is a large scale map?

Has higher detail over a smaller area

If the units on one side of the RF are in inches, what are the units on the other side of the RF?

Inches: they have the same units

What is a datum?

Mathematical model that describes the shape of the ellipsoid Tie the lines of lat and long lines to the model of the earth → defines the position of ellipsoid relative to the center of the earth

Do GIS data layers you download from the web have a coordinate system? Does ArcGIS Pro always know what it is?

Most of the time they do, sometimes they won't. ArcMap may not always recognize that coordinate system it is so you may have to define project it.

Do we use State Plane NAD27 or NAD83 in South Carolina and why?

NAD83 because this one keeps SC in one single zone, compared to the two zones in NAD27

What is NLCD/MRLC? What is its resolution?

National land cover characterization project • Multi-resolution land characterization • RESOLUTION = quality

What is a Representative Fraction (RF) and what does it represent?

Representative Fraction: a map scale in which figures representing units (as centimeters, inches, or feet) are expressed in the form of the fraction 1/x (as 1/250,000) or of the ratio 1:x to indicate that one unit on the map represents x units (as 250,000 centimeters) on the earth's surface.

What are the general parts of the recipe that makes up a coordinate system?

Shape of earth (ellipsoid or spheroid), datum (how the shape is tied to real world locations), projection type

What's an origin when talking about a projected coordinate system?

The base origin that you are measuring from (ex: equator)

What is a TIGER line file, what types of things does it represent? (vector or raster?)

Topographically Integrated Geographic Encoding and Referencing • Main source of data about the demographics of people • Roads and landmarks that are more current • Polygons that have people in them • Dictates what our natural environment looks like

What is a TIN and what is it used for?

Triangulated Irregular Network Used to visualize things in 3D Smaller triangles are used where there is more elevation change Larger Triangles are used to visualize flat areas

What are the Vector Data Structures?

Typically represents geographic features or entities as either points, lines or polygons

What does UTM stand for?

Universal Transverse Mercator

What types of data can be represented in a shapefile?

Vectors only (points, lines, polygons)

What is a map projection?

a way of representing the spherical Earth on a flat surface

map service

an Internet map that is available for viewing but that cannot be manipulated, symbolized, or saved by the user

What is metadata?

comprehensive, systematic, and deductive information about the content, structure, relationships, representation, and use context of the data stored in a database (DATA ABOUT DATA)

What projection does UTM use?

cylindrical

What are the three types of open geospatial web services?

data access data display data processing

where do lines of latitude start?

equator

What is the resolution of a raster data set with a 1 meter pixel size?

high resolution

Triangle example (from vector triangle to raster), what does it show us about what the Raster data structure is NOT good at representing?

irregularly shaped polygons ie. rectangle vs triangle

Are lines of Longitude equally spaced?

longitude lines are furthest from each other at the equator and meet at the poles

Does a DRG have an attribute table?

no

where do lines at longitude start?

pole to pole

Why do GIS data layers need to be in the same coordinate system?

so that the different layers line up

What's the difference between a spatial and non spatial query?

spatial- describe any data related to or containing information about a specific location on the Earth's surface non-spatial- data that is independent of geographic location

For Clip, Union and Intersect:

what does each do b. do they combine attribute tables between layers? c. What types of geographic features (points, lines, polygons) can be used with these processes ▪ Union combines two layers -- combining the data tables (usually applies to polygons) keeps all attributes ▪ intersect -- combines data tables BUT the end result is only in areas that overlays. Preserves line work within common extent and preserves all attributes. ▪ Clip -- clip theme is like a cookie cutter -- keeps just a part of the map that we want -- they don't combine data layers (can involve clipping out points, lines and polygons)

What's the default type of file used by ArcGIS Pro?

​Geodatabases

What does the dissolve tool do?

• Aggregating polygons (makes them bigger) → allows you to join together multiple adjacent polygons with the same value into a single larger polygon • Dissolve - Removing boundaries based on a common attribute

What is a digital orthophoto quad?

• Air photos • Resolution a few feet; can see with your eye what is there • Everything is corrected and scales made consistent

What is a DRG? (what GIS data structure is it typically in?)

• Digital Raster Graphics• Scanned USGS map -- georeferenced raster image

What is a DEM? (what GIS data structure is it typically in?)

• Digital elevation model - terrain elevations • Raster

How is Raster data represented?

• Divides the entire study area into a regular grid of cells in specific sequence → SQUARES

What is land cover, land use? (and what type(s) are represented in a GIS data set?

• Land cover: is what is there • Types: group covers, vegetation, bare soil, hard surfaces, water) • NLCD and MRLC • Land use: inferring what is going on there • Types: residential, industrial, commercial, farming/forestry, etc. Difficult to observe

In the geographic coordinate system: Which are lines of latitude, which are lines of longitude?

• Latitude: run parallel to the equator (aka parallels) • Longitude: pass through the North and South poles (aka meridian)

What is an ellipse or spheroid?

• Mathematical model that approximates the Earth's size and shape • Major axis lies in the earth's equatorial plane while the minor axis is coincident with the earth's spin axis

Why are there different types of projections?

• Planar (tangent line on the globe) • Conic • Cylindrical (mercator)

What items can be buffered?

• Points, lines, polygons • Used a lot for stream management zones, health studies, natural resources

What types of data are commonly represented by points, lines and polygons?

• Points: a spatial object with no area --> 0-D = location x,y. • Line: a spatial object with no area made by a sequence of points → 1-D = length • Polygons: a set of interconnected lines defining a close area → 2-D = area and perimeter

What things are commonly included in metadata and why?

• Who creates, when, scale, coordinate system, contact info • Without that, won't know what the data means could be useless for your use