Getting Started with GIS

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• It's functionality can vary greatly. 
• Systems analyze data, find patterns, and assess trends. 
• Geographic information = spatial (where - relative & precise locations using longitude & latitude) & attribute (what - like square miles, if a place allows rec activities,etc.) info.
• Data analyzes what's on top of what (overlay), what's next to what (proximity), what's connected to what (network).

1. How it Works
   1. Tools

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      • Find, use, create & share with others. Integrates hardware, software, data, people & workflows.    
      1. GIS Formats
         1. Maps

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            • analyze trends, find relationships, and assist with future decisions.
            • Mapping what is inside can assist with monitoring and assessment.
            •  Mapping what is nearby is often used in risk assessment and predictions
            1. Change

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               • Assess future trends. 
            2. Densities

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               •  Density maps can be used to condense large amounts of data analyzed for correlations and trends.
            3. Quantities

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               • Quantitative maps are often used to find trends; 
            4. Location

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               •  Locational maps can be used to determine where things are situated in relation to each other and are often used with navigation.
            5. Navigation

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               • Layers can be turned on & off & move. - The layer uses symbols to represent the collection of features. These features have the same theme, geometry, and set of attributes. Layers can be turned on and off and reordered. Moving the layers changes the order that they draw on the map. Layers can also be represented with multiple symbols based on their attributes Scale - Navigating the layers in a GIS map will change the map scale. Scale is the relationship between the size of a feature on a map and the actual size of that feature in the real world. Scale can be expressed as a ratio, such as 1:24,000. A 1:24,000 scale means that a feature on the map is 24,000 times smaller than its corresponding feature in the real world. Scale can also be expressed as an equivalence, such as 1 inch = 5 miles. A GIS scale is dynamic, which means that it changes each time you zoom in and out of the map. As the feature gets closer, the scale increases (becomes larger) and the reduction ratio decreases (larger scale = less reduction). Remember that these are ratios, so 1:24,000 is larger than 1:100,000. Pan tool to move around the map. Go back to previous extent tool to go back to previous position. Zoom in & out - Right click layer and zoom to layer. 
               • You can navigate a GIS map in two different views: the data view and the layout view. The data view is more commonly used when adding, editing, and analyzing the data. This view provides a table of contents that lists the map layers and can act as a legend. The layout view is like a "page view," and it is often used before printing or sharing a map. In this view, you can display map elements like titles, legends, scale bars, and north arrows.
            6. Projections

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               • 4 Spatial Properties: Shape Area Distance Direction  (azimuth)
               • Aspect is how the globe is tilted relative to the projection surface. Perspective is the position of the light source.  
               • A reference globe is created by wrapping a grid of lines, or graticule, around a model of the earth.
               • Using a mathematical formula, features on the reference globe's surface are transposed onto a flat surface. Coordinates on the globe are transformed into XY values on the "projected" map. Therefore, if two projections are based on different coordinate systems, each projection will have a different physical location for the same set of coordinates.
               • Distortions & Preserving Projections:  If a map preserves shape, then the feature outlines (like country boundaries) look the same on the map as they do on the earth. A map that preserves shape is conformal. Even on a conformal map, shapes are a bit distorted for large areas, like continents. Some projections preserve more than one spatial property:Conformal projections preserve shape, but they also preserve azimuth fairly well.Equivalent or equal-area projections preserve area and can also preserve distance reasonably well.  If a line on a map is the same distance (accounting for scale) that it is on the earth, then the map line has true scale. An equidistant map preserves true scale for all straight lines passing through a single, specified point. An azimuthal projection preserves direction for all straight lines passing through a single, specified point. Azimuth is measured in degrees of angle from north. So, the angle between a line that passes through the point of origin (A-B) and the central meridian (A-C) measures the same on a map as would on the earth. True direction is useful for navigation.
         2. ArcGIS Online

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            • GIS accessed over the Internet. Functionality = add shared geographic information to map locations and answer questions.
   2. Features

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      • = real world objects (trees, streets, landmarks) & phenomena (precipitation & elevation).
      • Metadata provides additional information about a feature and its attributes, such as a description of the data, who created the data, and its usage constraints.
      1. Vector

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         • Vector data is used to define objects with distinct boundaries, such as roads, parks, and land parcels. Uses 3 different geometries: 1. points - a single XY coordinate location. Each point has a longitude and latitude location (also referred to as geographic coordinates) that defines the precise location of the feature on the earth. 2. polylines - Defined by two or more locations that are connected with lines. Each location has a longitude and latitude (also referred to as geographic coordinates) that defines the precise location on the earth. 3. polygons - Defined using multiple locations that are connected and closed. Each location has a longitude and latitude (also referred to as geographic coordinates) that defines the precise location on the earth.
         • Vector data uses attribute information to determine what something is.  Attribute Table - Organized by columns and rows. Rows called records signify different features. Columns provide info about the features. Column header referred to as field, indicates type of info. Field types: String field contains text, date field contains dates, numeric field contains numbers, float field contains decimals.    
         • Vector data types can be stored in a folder or in a geodatabase as a geodatabase feature class.
      2. Raster

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         • Not every object or phenomena has distinct boundaries. Precipitation, heat from a forest fire, and imagery are all examples of features and phenomena with a continuous surface, without a defined outline. A continuous surface describes a surface where every location has a value, and every value could be unique (for example, elevation). A GIS represents this information using a raster data model. A raster is made up of equal-sized cells arranged in rows and columns. The raster has an origin (real-world location). A GIS uses the origin, relative cell location, and cell size to determine the location of the cells on the earth. Each cell in a raster stores a value. The value can represent a continuous measurement, such as elevation, or a discrete value, such as land cover. Discrete rasters can have values that represent a code for a particular category. In this case, cells with the same value are counted and stored in the raster's value attribute table (VAT).
         • Raster data types can be stored in a folder as a raster dataset or in a geodatabase as a mosaic dataset. A mosaic dataset is a collection of multiple rasters that acts as a catalog. The rasters are indexed so that you can easily query and search for the data.