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EES 202 Exam 2 Study Guide
Terms in this set (46)
What is the difference between an attribute table and a stand-alone table
Attribute Tables contain information about features in a geographic or spatial dataset. Standalone tables contain information about one or more objects in tabular format, but no info about the map features.
What is an event theme in ArcMap, and how is it created?
A theme is a set of geographic features in a view. A theme represents a source of geographic data such as: A spatial data source such as an ARC/INFO coverage or ArcView shapefile. A CAD drawing such as an AutoCAD drawing
Numerical data is data that is expressed with digits as opposed to letters or words. For example, the weight of a desk or the height of a building is numerical data. Numerical data can be broken down into two different categories: discrete and continuous data.
A text string, also known as a string or simply as text, is a group of characters that are used as data in a spreadsheet program. Text strings are most often comprised of words, but may also include letters, numbers, special characters, the dash symbol, or the number sign.
Date Data examples
A coverage or shapefile stores dates in a date field with this format: yyyy-mm-dd. A geodatabase formats the date as datetime yyyy-mm-dd hh:mm:ss AM or PM. Settings on your Windows system determine how the dates are displayed in ArcMap—M/d/yy, MM/dd/yy, yy/MM/dd, and so on.
Time Data examples
Enabling time on your data After you have added your temporal dataset, its time properties have to be set in order to visualize it through time using the Time Slider in ArcMap, ArcGlobe, or ArcScene. Time properties on the layer can be enabled by simply checking Enable time on this layer on the Time tab of the Layer properties dialog box.
Binary data examples in ArcMap
The Binary Thresholding function creates a raster output that divides your raster into two distinct classes. The algorithm behind the Binary Thresholding function, the Otsu method, was designed to distinguish between background and foreground in imagery
cardinality" is a setting that can be applied to joins in calculation views. It specifies how many matching entries for entries of one table exist in the other table of a join. It consist of two numbers, the left number describes the number of matching entries for entries of the right table while the right number describes the number of matching entries for entries of the left table.
What is the "Rule of Joining"
All tables link with each other based on cardinality (1-1, 1-M and M-N). Both join and relate work on the principal of having matching unique IDs in two tables.
While join is particularly useful for 1-1 relationships, relate is ideal for 1-M relationships. The rule for joining is based on if there are matching attribute tables to pair with.
Describe a JOIN operation between 2 tables. What is necessary to do a JOIN? What is the simplest relationship for a JOIN to occur.
A join expression consists of a left-hand and a right- hand side, which are joined either by means of INNER JOIN or LEFT OUTER JOIN. Depending on the type of join, a join expression can be either an inner (INNER) or an outer (LEFT OUTER) join. Every join expression can be enclosed in round brackets. If a join expression is used, the SELECT command circumvents SAP buffering.
Describe how a RELATE is created between 2 tables.
Once a database is normalized, relationships between the data in multiple tables must be established. A hefty part of designing a relational database is dividing the data elements into related tables. Once you're ready to start working with the data, you rely on relationships between the tables to pull the data together in meaningful ways.
What are the 3 GPS Segments that compose the satellite-based positioning system?
The Global Positioning System (GPS) is a U.S.-owned utility that provides users with positioning, navigation, and timing (PNT) services. This system consists of three segments: the space segment, the control segment, and the user segment. The U.S. Air Force develops, maintains, and operates the space and control segments.
What is the basic principle (equation) behind GNSS positioning?
The basis of all GNSS systems is that a user determines it position by measuring to at least 4 GNSS satellites at the same time.These measurements give the user 4 distance measurements between himself and the 4satellites. With four measurements one can resolve 4 unknowns. For the end user these 4 unknowns are the 3 unknowns of his position (X, Y, and Z or Latitude, Longitude, and Height) and the clock error of his GNSS receiver.
What is 'ranging'?
Method of locating or establishing intermediate points on a straight line between two fixed point or two survey stations is called as ranging. There are two methods of ranging Direct Method (Two ends of survey line or stations are inter-visible) Indirect Method (Two ends of survey line or stations are not inter-visible)
Briefly describe how trilateration works for determining position.
As GPS satellites broadcast their location and time, trilateration measure distances to pinpoint their exact position on Earth. While surveyors use triangulation to measure distant points, GPS positioning does not involve any angles whatsoever. Through the measurement of distances, your precise GPS location can be determined.
How many satellites must be available to obtain a 3-dimensional (XY location & elevation) position fix?
If you had three satellites, the locus of distance from all three would be two points on that circle. And you need a fourth satellite to distinguish between those last two points. Since most people ignore altitude, the surface of the earth provides the necessary "fourth" sphere in 2-d applications, meaning you generally need only 3 satellites for most navigational problems.
. Why is it necessary to have extremely accurate clocks for timing?
The satellites are not in geostationary orbits, which means they are over different points of the Earth at different times . To know where a particular one is when using it to get a position fix, you have to know when it is.
What are the basic differences between the CARRIER SIGNALS and the CODED SIGNALS that are transmitted from the satellites?
a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave usually has a much higher frequency than the input signal does. The purpose of the carrier is usually either to transmit the information through space as an electromagnetic wave, or to allow several carriers at different frequencies to share a common physical transmission.
What is "Almanac" data used for?
The GPS almanac is a set of data that every GPS satellite transmits, and it includes information about the state (health) of the entire GPS satellite constellation and coarse data on every satellite's orbit. This information is known as the ephemeris data.
what is DOP?
Dilution of precision (DOP), or geometric dilution of precision (GDOP), is a term used in satellite navigation and geomatics engineering to specify the Error propagation as a mathematical effect of navigation satellite topology on positional measurement precision. 1 Introduction 2 Meaning of DOP Values
What is PDOP?
GDOP (geometric dilution of precision) or PDOP (position dilution of precision) describes error caused by the relative position of the GPS satellites. Basically, the more signals a GPS receiver can "see" (spread apart versus close together), the more precise it can be.
What are some potential sources for GPS error?
Clock Inaccuracies and Rounding Errors
When did NAVSTAR become fully operational?
DoD then followed through and launched its first Navigation System with Timing and Ranging (NAVSTAR) satellite in 1978. The 24 satellite system became fully operational in 1993.
How many satellites are currently in the system?
The constellation requires a minimum of 24 operational satellites, and the official target count is 33.
What agency manages the Control Segment?
The Control Segment of GPS consists of: Master Control Station: The master control station, located at Schriever Air Force Base in Colorado Springs, Colorado, is responsible for overall management of the remote monitoring and transmission sites.
What country operates GLONASS?
GLONASS is the most expensive program of the Russian Federal Space Agency, consuming a third of its budget in 2010. By 2010 GLONASS had achieved 100% coverage of Russia's territory and in October 2011 the full orbital constellation of 24. A total of 26 satellites
Describe the basic principle behind "differential correction".
Differential correction techniques are used to enhance the quality of location data gathered using global positioning system (GPS) receivers. Differential correction can be applied in real-time directly in the field or when postprocessing data in the office. Although both methods are based on the same underlying principles, each accesses different data sources and achieves different levels of accuracy. Combining both methods provides flexibility during data collection and improves data integrity.
What is WAAS?
The Wide Area Augmentation System (WAAS) is an air navigation aid developed by the Federal Aviation Administration to augment the Global Positioning System (GPS), with the goal of improving its accuracy, integrity, and availability. Essentially, WAAS is intended to enable aircraft to rely on GPS for all phases of flight, including precision approaches to any airport within its coverage area. It may be further enhanced with the Local Area Augmentation System (LAAS) also known by the preferred ICAO term Ground-Based Augmentation System (GBAS) in critical areas.
Define 'remote sensing'.
Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object and thus in contrast to on-site observation, especially the Earth.
. What is the electromagnetic spectrum?
the range of wavelengths or frequencies over which electromagnetic radiation extends.
What are the principle wavelength regions?
Wavelength Regions. The electromagnetic spectrum ranges from the very short wavelengths of the gamma-ray region (measured in fractions of nanometers) to the long wavelengths of the radio region (measured in hundreds of meters).
vertical aerial photograph
Vertical aerial photograph is an aerial photograph technique where the shots are taken from directly above the subject of the image. Hence, this method of aerial photograph is also often referred to as "overhead aerial photograph
oblique aerial photograph
an oblique photograph is one which has been taken with the camera axis directed at an inclination to the ground.
Stero/3d aerial photograph
Stereopair photographs provided a way for 3-dimensional (3D) visualisations of aerial photographs; since about 2000, 3D aerial views are mainly based on digital stereo imaging technologies. One issue related to stereo images is the amount of disk space needed to save such files.
What is 'parallax'? How is parallax typically achieved for aerial photos?
Parallax is an apparent displacement or difference of orientation of an object viewed at two different locations during vertical aerial photography. The objects at a higher height lie closer to the camera and appear relatively larger than similar objects at a lower elevation. The tops of the objects are always displaced relative to their bases.
What are the 2 major sources of distortion in aerial images?
Relief displacement, camera tilt, camera film and lens errors, and the atmosphere
List the 6 basic factors used in photo interpretation.
location, size, shape, shadow, tone/color, texture, pattern, height/depth and site/situation/association
What does "ground truth" mean?
ground truth" refers to the accuracy of the training set 's classification for supervised learning techniques. This is used in statistical models to prove or disprove research hypotheses. The term "ground truthing" refers to the process of gathering the proper objective (provable) data for this test.
Define the 4 types of resolution for satellite sensors.
here are four types of resolution when discussing satellite imagery in remote sensing: spatial, spectral, temporal, and radiometric.
How often does Landsat 8 cover the same area?
The orbit of Landsat 8 is such that it covers the save area on the earth every 16 days. To determine when Landsat 8 is going to pass over your area of interest you first need to determine the path and row of the image that covers your area.
How often does MODIS cover the same area?
every one to two days
What is Lidar data?
a surveying method that measures distance to a target by illuminating the target with laser light and measuring the reflected light with a sensor. Differences in laser return times and wavelengths can then be used to make digital 3-D representations of the target.
What is the primary use of Lidar data?
obtaining Digital Surface Models (DSMs) of the earth's surface.
What is a Variable Distance Buffer?
A buffer based on different distances is called a variable buffer. For example, the noise level surrounding surround a street network may be based on the traffic load. Therefore a variable buffer may be used to illustrate the noise level by using a larger distance for high traffic roads and a shorter distance for quieter roads.
What is required to calculate the buffers?
If the input features have a geographic coordinate system and you specify a Buffer Distance in linear units (meters, feet, and so forth, as opposed to angular units such as degrees), geodesic buffers will be created. This option produces the same result as the Buffer Tool prior to ArcGIS 10.3.
Describe the CLIP overlay operation
Use this tool to cut out a piece of one feature class using one or more of the features in another feature class as a cookie cutter. This is particularly useful for creating a new feature class—also referred to as study area or area of interest (AOI)—that contains a geographic subset of the features in another, larger feature class.
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