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What is Geographic Information Systems?
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When did GIS begin? And where?
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GIS
Notes for Exam 1
| Question | Answer |
|---|---|
| What is Geographic Information Systems? | An electronic map tied to a database.Needs: Hardware, Software, Data, People |
| When did GIS begin? And where? | IT began to take off between the 1950's and 60's using a computer. Canada. |
| Who is the godfather of GIS? | Dr. Roger Tomlinson, tried to put all maps put into computer. |
| Types of Key maps. | Scanned maps, Vectorized scanned maps, topological systems, attribute table. |
| What institute brought people together? | Harvard. |
| What was the name of the first GIS software package? | Symap |
| Jack Dagermond made which company? | Environmental Systems Research Institute (ESRI) |
| What is a map? | A map is a 2-D representation of something on the surface of the earth. |
| What is looked for on a map? | Distance, Direction, Size, Shape |
| Types and definition of types of maps | General- emphasis on location, Thematic- single subject |
| What is a scale? | the relationship between distance measured on the map and distance on the ground. |
| 3 types of scales | Graphical scale- graduated bar, Verbal scale-linch=200feet, Fractional scale- compares map distance to ground distance by proportional numbers and is expressed as a ratio. |
| What are the 7 map essentials? | Scale, Title, Date, legend, direction(north arrow), location material, metadata(data about data- who created it? where did it come from?) |
| What are 3 datums? | NAD27, NAD83, WGS84 |
| By how many feet are NAD and WGS off? | 200 feet |
| Explain a Mercater map. | Preserves direction and shape. Sacrafices distance and area |
| Explain a Peters Projection map. | Preserves area. Sacrafices shape distance and direction. |
| What does an overlay have? | Projection, coordinates, data |
| Measurments north and south of equator. | Latitude |
| Angular measurements west and east if prime meridian. | Longitude |
| What is a project? | multiple data sets, symbology, layouts, pathes |
| What is data? | Indivual themes |
| What is a Raster Model? | deals with pixels, overlay a grid on map |
| What is a Vector Model? | -Points (X,Y) coordinates-lines, series of points-polygons, an enclosed line |
| Examples of Geographic Data | location, points lines, polygons, pixels |
| Name types of Geographic Attributes | Descriptions linked to location, nominal, ordinal, interval, ratio |
| What is Nominal? | One that serves only to identify and entity from another |
| What is Ordinal? | Values that have a natural order |
| What is an interval? | Value differences make sense |
| What is a ratio? | Simular to interval has no arbutary zero |
| What is data classification? | Group the data 3-10 |
| What is equal interval? | dividesthe full range of attributes into equally sized subranges.(good for presentations) |
| What is quantiles? | ID breakpoints between classes so that each subclass ha the same amount of data. |
| What is natural breaks? | Using statistics ID breakpoints between classes to form subgroups "naturally" |
| What is frequency distribution? | an ordered array that shows the frequency of occurance of each value. |
| What is a Histogram? | Graphical frequency distribution |
| Make a histogram using these numbers 1,1,2,4,5,7,11,15,16,16,16,20,22,22,23,26,27,29,30,30 | 0-5=5=.25, 6-10=1=.05, 11-15=2=.1, 16-20=4=.2, 21-25=3=.15, 26-30=5=.25 |
| What is mode? | Most frequent number |
| What is the median? | Middle number (make sure to put number in order) |
| What is mean? | Average |
| Find the mode, median, mean, standard deviation, +1s, -1s, and final answer of 100,90,80,75,20 | mode=0 or all, median=80, mean=73, standard deviation=31.14, +1s=104.14, -1s=41.85, final answer=4 out of 5 data are within +/-1s |
| What is topology | branch of mathematics that deals with relationship between points. (points-nodes) (lines-arcs) (polygon in 2-d space) |
| What is a node? | point created by intersecting lines or at the beginning or end of line. |
| What is connectivity? | ID of interconted lines. |
| What is Contiguity? | ID of which polygons touch each other(shared arcs) |
| What is Area Definition? | ID of areas by a set line. |
| Who created the GPS? | Department of defense. |
| How many satellites are used for GPS? How many are needed? | 24 used, 21 needed |
| 3 things on a satellite | computer-flight and function of satellite, Atomic clock- accurate time, Radio transmitter-signals |
| Advantages and disadvantages of a C/A code | Advantage- quick, disadvantage- less accuate than P code, and can be jammed or spoofed |
| Advantages and disadvantages of P code | more accurate, not difficult to spoof or jam |
| Control segment interference to satellites | control staions |
| What does a receiver do? | receieves data |
| approx. position of satellite | almanac |
| Precise position of satellite | Ephemeris |
| How many satellites for Location? | 3, lat/long |
| How many satellites for position? | 4, lat/long and elevation |
| What is a waypoint? | Stored location in receiver. |
| What are WAAS? | signals from airport, produced by FAA |
| What is differential GPS? | loading your waypoints to compare with stored location |
| Convert 43degrees 41min 31sec to decimal degrees | 43.0753 |
| Convert 89.40062 to DMS | 89degrees 24min 2.32sec |
| Air photo with coordinates | Digital orthophoto quad (DOQ) |
| can see elevation | Digital Elevation Model (DEM) |
| series of vectors | Digital Line Graph (DLG) |
| topographic map | Digital Raster Graphic (DRG) |
| Metadata needed to document | ID info, Data quality, Spatial data org, Spatial ref. info, entity and attribute, distribution info, metadata ref. info |
| Title area covered keyword | ID info |
| Horizontal and vector accuacy, completeness | Data Quality |
| Raster/Vector | Spatial data org. |
| lat/long, coordinate, projection, data | Spatial ref info |
| Definition of entity and attributes | entity and attribute |
| Fees, files format | Distribution info |
| Who created the metadata? | Metadata ref info |
Created by:
jrw4274
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