Computer hardware, software, geographic data is. used to capture, maange, analyse and display.

• Geographically reeferenced information
  

With GIS you can link information, layer information. and choose what layers to combine to answer questions.

Features grouped. in layers have same shape and same characteristics. They are located within the same geographic extent.

One coordinate pair, 2 coordinate pairs or more, one or more lines whose start and end coordinate pairs are the same.

Are drawn on top of each other to create an informative gis map

Polygons: objects within boundaries, ex: countries, building footprints, lakes

Lines: objects too narrow to be polygons, ex: streets, rivers, telephone lines.

Points: objects too small to be polygons, ex: cities, trees, hospitals.

Each feature is a record or row; each attribute is a column or field

Every feature has an ID, one-to-one relationship between feature, identifier and attribute record.

Locations, descriptions of geographic features; a combination of spatial data and descriptive data.

Geospatial data. can be linked to other non-spatial datasets. (Time is optional)

Determining new positions with respect to existing reference features.

The science of deriving information about the earth from images acquired at a distance.

GPS receivers use information to calculate location (extremely accurate)

Can be used with any database containing a locational attribute

Must use predefined resolution, efficient for storying dense datasets, deals poorly with linear features, only one attribute value per layer.

Efficient for use and storage of sparse datasets, tends to be more precise / higher resolution, deals well with exact boundaries, processing times can be high with complex datasets.

Every cell could potentially have a unique value: Ex: elevation, Temperature, cell phone signal strenght.

Categorical data, well-defined boundaries, depending on type it may have. associated values.

Can be any size you define. Smaller ceells have higher resolution (less. generalization), but the smaller the cell size means larger file size and longer analysis times.

Many data sources = data at many different scales, this is common and poses challenge for interpretation & analysis.

File format is the mechanism of how. data is stored on the computer, it indicates to the system where to look for various pieces of information.

Advantages: ESRI is the standard so other software knows how to deal with it.

Disadvantages: Size limitations (2Gig), holds only vector data, no topology, only holds simple geometries (points, lines polygons)

There are 3 kindsL Personal geodatabases. (.mdb), File geodatabase - directory, ArcSDE geodatabases - uses. external RDBMS.

Think of it like a container used. to hold all the colleciton of datasets.

Disadvantages: It. is proprietary format (only ESRI can fully read it).

Advantages: Keeps all of your data together (shapefiles only have 1 dataset. in. it) Size limits. are bigger in file/ArcSDE geodatabases, they can hold both simple and complex. geometries, both rasterand vector. data, and multiple people looking at same data at once, its also faster and better compression then shapefiles.

ESRI Internal Format: Grid, ASCII - needs. to be converted (.TXT, .ASC), other supported formats. = TIFF, JPEG.

Not practical for most applications due to size, lack of detail, only one side. of the earth is visible at one time.

A. model of the shape of the earth that is approximately the shape of. a sphere (flattened at the poles)

The primary use is to locate position (it is a requirement. for position in GIS)

Spheroids/ellipsoids can be used to represent the earth. Many. There are many different spheroids/ellipsoids.

With coordinate systems, datums specify which spheroid/ellipsoid is being used to model the earth.

A measurement base model of the shape of the earth based on gravitational pull

They do not look perfectly spherical, they have rough surface.

Also known as reference systems: tell use where features (points, lines, polygons or raster is located)

Data is defined by both horizontal and vertical coordinate. systems.

horziontal - north - south and east - west tell locate data accross surface of the earth.

Vertical coordinate system - locate relative height or depth of data.

Known location used to determine feature locations: 2 types: geographic, projected.

Longitude and latitude are angles measured from the earths centre to a point on the earths surface.

Latitude lines are parallel and run east to west and around the earths surface, and measure distances. from. north and south of the equator.

Longitude lines run north and south, around the earths surface and intersect at the poles, measures distances east and west.

A line of longitude. designated as 0 degrees east and west, to which all other meridians are referenced. Today the prime meridian runs through the Royal Observatory in Greenwhich England.

Changing from round to flat results in distortion (This is unavoidable)

Every map. has distortion: map of small area - less distortion, map of large area - greater distortion

Choosing a map projection means choosing your distortion: Shape, Area, distance, Direction. Only.a globe can preserve all four

Features: Straight Parallels and meridians that meet at right angles. Good for navigation. If mapping the world in this projection there is significant distortion toward the poles. Best known projection of this type is Mercator.

Feautres: Parallels are represented as circular arcs. Meridians. are represented as straight radiating lines, Typically used for mid-latitudes (for maps of Canada)

Can be sub-classified depending. on where the perspective is. Gnomonic - from the centre of the earth, Stereographic - from. the opposite pole. Orthographic - from an infinite point in space.

Conformal: Correctly shows the shape of features (A map can not be both equal area or conformal - it can only be one; or the other; or neither)

Equidistant: Correclty shows distance between two features.

True Direction: Corrcetly shows the direction between two features.

Choosing a map projection: Ask yourself what is the purpose of this map. Decide on a class of projection: tropical region - cylindrical, middle latitude - conic, polar region - azimuthal

Measurement expressed in degrees, minutes, seconds or decimal degrees

latitude and longitude converted. (projected) to planar coordinates.

Locations ar emeasured with an x and y value from a point of origin.

Goal is accurate analysis (measure distance, caluclate area, shortest distance)

This method of projection works - as long as your datasets share the same geographic coordinate system. If there. isn;'t misalignment may occur.

Works on Vector Data: points, lines and polygons.

Select by attribute: Allows you. to select things. by. attributes using clauses. You can select multiple by using different equations.

Select by Location:Select.attributes inside of a given location you set.

Export to Feature Class: Way of exporting things so that it creates a new layer inside the geodatabase.

Buffer: Buffer creates a polygon around a point, line or polygon.

Clip: Use this tool to. cut out a piece of one feature class using a polygon feature class as a cookie cutter. It must be a polygon.

Multiple Ring Buffer: Similar to the buffer tool but you. can create multiple rings around it.

Erase: Does the opposite of the clip tool, it erases selected portion of the features.

Dissolve: Aggregates features based on specified attributes. To eliminate the lines between adjacent similar polygons.

Merge: Combines two or more data layers of the same type (point, line or polygon) to form one layer containing all data, including attributes. If there are

Intersect: Identify areas where all input datasets exists. New features will contain attributes of all input. files. No overlaps will exist.

Union: Identify areas where any input dataset exists. Overlap areas will have attributes of all input features. Areas where there is no overlap will be maintained with appropriate attribution.

Hue: The colour dimension described by different wavelengths of the electromagnetic spectrum; associated with differences in kind (qualitative).

Value: How light or dark a colour appears vs. black and white, Ex: Yellow has the brightest brightness, but the lowest value compared to white.

Saturation: Perceived amount of white; single hue progression. Ex: From white to Red.

Chroma: For a given hue, the perceived percentage of grey (how washed out it is.).

Used on computer screens, televisions, it is additive since to make white you have to add all colours.

Used for printing books, magazines, etc. It's subtractive since to make white you add no colour.

Different qualitative/quantitative data need unique representation, make some things pop and others recede. Helps the viewer organize the elements of an image.

Also arrangement, composition or layout, starts with the best fit for mapped area. Ex: Chile is long and skinny, so a portrait map would work better.

Points: Keep space around each label, space between the point and label, orientate the label 45 degree angle from the point, never directly in front or behind the point. With linear features keep labels on the same side as point.

Areal Features: If inside is not possible, treat as a point. Fill space when possible.

Masks: Shapes filled with the predominant background colour when you cannot avoid overlapping labels with complex features. (Called HALOS in ArcGIS).

Typeface and fonts matter, choosing between serif and sans-serif, etc.

Conventions: 6pt is the lower limit for most publications, 8-12pt is the most common range for publications, 28-38pt for screens or posters, 2pt difference at small sizes, 3-4pt difference at larger sizes.

Viewshed: Ensure spatial analyist license is on. Allows you to find where a place is visible. from.

Raster to Polygon: Converts a raster layer to a polygon (Do not use simplified, it will give inaccurate numbers).

Raster Calculator: Use statements to calculate a new raster layer from other layers.

Reclassify: Reclassifies the value of the raster (Ex: change it from o to a 1, etc.).

Hillshade: A hypothetical illumination of a surface represented by shadows on a map that simulate the effect of the sun's rays and created a 3D effect on the map.

Slope: How. fast the vertical height. is changing