GIS Questions and Answers Already Passed

GIS Questions and Answers Already Passed What is GIS A system with spatially referenced data with meaning behind the data using explicit links. What questions are unique to geography and therefore GIS? questions related to trends, location, conditions etc Why is GIS called an "enabling technology"? because you can use it with several different disciplines. What industry is the biggest spender on GIS and why? Utility companies because they need their databases current and up to date. What industry was the found, or earliest developer, of GIS technology? Environmental applications What is an example of a business GIS? Market share analysis, insurance, fleet management, retail site location What industry is the largest in therm of number of users/installations of GIS? Government What is cadastral mapping and the system that is used in this type of mapping? *Provides detailed information about real property within a specific area (a map of of parcel boundaries). *Maintained by the government *public record What is geodesy? The science of measuring and representing the shape and size of the earth, and the study of its gravitational and magnetic fields What is AM/FM Automated mapping/facilities management - utility companies use this What are complex linear GIS applications called? Dynamic segmentation - combines lines and measurements (ex: miles) to create complex line features What are the 5 components of a GIS? (1)Hardware (2)software (3)spatially referenced data (4)people (5)policies/procedures to keep it updated What are the 4 GIS software subsystems? (1) Input (2) Management (3) Analysis (4) Output What are the 2 GIS data models and define their characteristics (1) Vector data model - has finite boundaries, does not change, discrete/entity; Advantages: has topology, can store multiple feature types Disadvantages: old format, file structure difficult (2) Raster data model - broad, changes gradually, no finite boundaries, continuous, field view; Advantages: easy to understand, rapid retreaval, quick drawing, powerful operators; Disadvantages: not good at representing points and lines, files can be huge, mixed pixels. What makes GIS different from all other software? the ability to perform a spatial analysis; connectivity, containment, contiguity, topology, proximity and direction What is TIGER data and where did it come from? Topologically Integrated Geographic Encoding and Referencing; used in the 1990's for US Census data, created by merging DIME files and DLG's; includes roads, street names, and address ranges What types of features are used to define vector data? *points, nodes, vertices, centroids=dimensionless, has location, point features. *lines=1 dimension, has location and length, made up of nodes and vertices *areas=2 dimensions; has location, length, area, boundary, made up of lines (polygons) *regions=complex polygons What are examples of complex vector feature types? dynamic segmentation, routes (a collection of line features, attributes called events) What is GISci? Geographic Information Science - used more for science/research behind geospatial technology What is topology? the storage of spatial relationships inside data; can determine spatial relationships such as nearness, direction, contiguity, connectivity, and containment What is the FGDC and what three major developments has it created? Federal Geographic Data Committee; created a metadata standard, created a spatial data transfer standard, created a clearinghouse node network What historical landmarks have shaped the development of GIS? 1980 Census What is the difference b/w entity and field views of reality and how does this translate to a data model? entity views are in vector format, they have distinct boundaries; field views are in raster format, the features vary across the landscape What two components make up all geographic information, or data, stored in a GIS? spatial location and attributes What are the types of entities we store in vector data? trees, buildings, roads What is the georelational data model? is there a relationship between map data and attribute data? If so, what is this relationship? The explicit link is the relationship between the map data and attribute data. What are the complex vector entities? routes, regions, areas, lines, vertices, nodes, points What is a TIN? Triangulated Irregular Network - What are coverages, shapefiles, and geodatabases and how do these types of files store information? Coverages stores topology and mutliple types of features in one data set; Shapefiles are composed on multiple files, can only store one type of feature, does not store topology; Geodatabase uses an ojbect-oriented relational database model, all types of data can be stored including vector and raster In ArcMap, do all data layers in a data frame have to be projected to the same coordinates system in order to make a map? yes What are some common file formats for the vector and ratser data models? vector: Raster: GRID format The FGDC defined a file format to be a standard for all federal and state government agencies. What is this file format? The Spatial Data Transfer Standared (SDTS) What is the raster data model and how is it stored on the computer? *GRID-Native raster file format *DEM-Digital elevation model, in grid format *DOQ-Digital Orthophoto quad: rectified aerial photograph *DRG-Digital raster graphic: scanned USGS topo georeferenced to UTM. What techniques are there to compress raster data? Run length encoding block encoding chain encoding Do you know how to convert a USGS DEM to a GRID? ArcToolbox Waht is a false-color composite? used to show temperature; things that are not within the visible spectrum What is Landsat MSS and TM? *Landsat MSS-Multiple Spectral Scanner *TM-Thematic Mapper; 30mx30m, spectral resolution, good for vegetation What is SPOT? AVHRR? *SPOT-a french satellite, poor spectral, used for URBAN *AVHRR-Advanced Very High Resolution Radiometer, good for oceanography What is rectification? the process of converting a raw image into an image with a projection What are attribute data and how do they relate to spatial data? *Attribute data describes spatial data, can be unlimited *Relational Database Management Systems (RDBMS) store non-redundant data tables *Each geographic feature has one record (row) the same number of columns (fields), and each field is a single ATTRIBUTE What are the different types of attribute data and can you define them? *Qualitative: Information tells you what things exist * Quantitative: information measures the magnitude of things What are the different measurement scales? *Nominal (qualitative): categorical (habitat types, land use) *Ordinal (quantitative): ranked data (small, medium, large) *Interval (quantitative): ordered values (temperature) *Ratio (quantitative): ordered values with a known zero, compare them using mathematical properties can use math to compare the values (population density, area) *Cyclical (Quantitative): direction, used to characterize directional attributes such as aspect, degrees on a compass Can you describe the difference between the hierarchical and relational database models? *Hierarchical data structures are the most traditional methods of storing data, flat files *relational data models superior to hierarchical because minimize redundancy, better for updating, more analytical and complex How do you normalize data and why? When you have a percentage of a variable per land area or something that is easily comparable among maps Is it better to have redundancy or remove redundancy? Remove redundancy How do you create relationships among tables? Do you understand the difference between relates and joins? *Must know which table is the destination and which is the source; destination is where the geology is! *Joining: brings two tables together; appear as one but use two different files *relating: establishes a linkage between two tables but they remain separate *Four types: one-to-one, one-to-many, many-to-many, many-to-one. relating tables must have a common field Do you know how to add a table of X,Y coordinates and turn it into a data layer? File>Add Data>Add XY Data, Open table (define coordinate system Do you kno how to add a field and calculate field values Open attribute table>table options>add field>write new field name>ENTER>Right-click>Field Calculator>enter equation What is a map projection? *the process of transforming the spatial relationships and map features on the Earth's surface to a flat map with Cartesian coordinates. *A systematic rendering of geographic coordinates that allow a sphere to be transformed to a planar surface with Cartesian Coordinates What is the difference between large and small scale maps? *Large scale maps show more detail but less on an area, also called fine scale maps *Small scale maps show more area but less detail, called broad-scale maps What is the spherical coordinate system? Locations on a globe are defined by a geographical coordinate system using latitude and longitude Give an example of a planar (or projected) coordinate system *measurement in 2 dimensions, each system uses a projection, datum, map unis, and other parameters *developed to transform spherical coordinates to planar *UTM-Universal Transverse Mercator gird: a series of the transverse mercator projections that extend a flat grid *SPCS-State Plane Coordinate System: a system that divides the US into about 120 zones, to minimize distortion What are lines of longitude and latitude? Latitude=parallels Longitude=meridians What are meridians and parallels? Graticle Do you know the four properties of projections? distance, area, shape, proximity Distortions: equidistant (distance), Azimuthal (direction), Conformal (shape), Equal Area/Equivalent (area) Do you know the three main types of projections? *conical-works by making a hat (cone) and placing it on the globe *cylindrical-works by wrapping a piece of paper around the globe, then unrolling it to make a map *Planar-works by laying a plane on top of the globe, touching at only one point What is a conformal projection? ... What are lines of tangency? line that represents the location where the image is lifted form the spherical map, at one location the image has the least amount of distortion and increases with distortion away from that point What is a datum and give examples? *describes the shape of the earth, the topography, defines the position of a spheroid in relation to the center of the Earth and establishes a reference frame for measuring locations on the surface. *Spheroid: also called ellipsoid is a mathematical model or equation of the earth *Clark 1866:a spheroid based on old measurements *NAD27: a datum that uses the Clarke 1866 spheroid *WGS84: spheroid that uses satellites and GPS derived measurements *NAD83: a datum that uses WGS84 spheroid There are many ways of using projections in GIS. Know the types of projections Define: what it is and this is required to project the data properly; Project: is what you want it to be What are the two main types of maps? *Reference Maps: gives the location of something, only giving geographical information (ex: USGS topographic maps) *Thematic: using spatial relationships to share information (population, land use) includes chloropleth, isoline, flow, bivariate, and others What is a chloropleth map? uses color to classify the variables in a geographic region What's the difference between graduated circle/symbol maps and dot density maps? *Dot Density: randomly located points within enumeration areas, least popular and most confusing, represent an area, *Graduated circle/symbol: represent actual locations or can be set at the centroid of the polygon, represent actual place and density of the area What are the required and optional map elements? *required: title, neat line, north arrow, geography, legend, scale bar, source/ancillary text *optional: graticule, inset map, annotation What are class intervals and what are the different methods for defining class intervals? *Equal interval: classes are of equal width or size *Percentile/quartiles: same number of observations in each class *natural breaks: uses a histogram to lump into data classes Why is cartography considered both an art and a science? you are able to effectively display the data/geography to relay a message What are attribute queries? the most common method of interacting with spatial vector data What are geographic/spatial queries? *Search for locations, user-defined or irregular polygon, select by spatial relationship (theme), What is Boolean algebra and do you know what the different operations mean? AND, OR, NOT, XOR What statistics are commonly computed in GIS? Simple Summary Statistics: minimum, maximum range, mean (average), standard deviation How and why is the raster calculator different from the search by attributes tool? raster queries are by cell value and by graphic What types of data can be imported/converted/digitized? ... What are the different methods of digitizing? ... What types of errors are there (in vector data), how would you find them and how do you fix them? *Duplicate lines, tolerance, dangles, finding intersections, doubling digitizing, overshoot and undershoot, unclosed polygons, pseudo nodes *Global edit using a specified tolerance (dangle and fuzzy) *Local, patching a gap, eliminating slivers, clipping features Name the various types of analytical functions? Summary statistics, proximity analysis, transformation tools What is the difference between raster and vector spatial analysis? *Vector: use distance, buffer, overlay, reclassification, dissolve, networking and dynamic segmentation, complex overlapping polygons (regions) *Raster: functions that work on local, neighborhood, zonal, and global perspectives of your data, terrain analysis: slope aspect, visibility, watershed analysis, spatial interpolation, predicting surfaces such as precipitation How do you calculate the area of a polygon? ... How does the buffer tool work and what are the many optons for its calculation? creates polygons around a feature to delineate a distance. How does map overlay owrk? What are the many types of overlay functions? calculates the geometric intersection of two or more themes, can combine attributes, makes new geometric features *Union (or), intersection (AND), and Identity. What is EDA and why is it an important component to GIS research? *Exploratory Data Analysis: data centered query and analysis, look for trends and relationships, data mining