Re-introduction to GIS ENVS 420 Re-introduction to GIS

What is a GIS The systematic integration of technology, geographic core ideas, and specialized knowledge applied through procedures to compile, store, manipulate, and analyze spatial and temporal data, and to communicate these data and information through some form of geovisualization.

What is a GIS? Smaller/ practical definitions ‘Layers’ of information about a place that give a better understanding of that place. An information system designed for data referenced by geographic coordinates. A set of tools for analyzing spatial data

What distinguishes GIS from other technologies? GIS used to manage and analyze spatial data   GIS predicates processing functions on geographic location   types of data involved types of users and user support required specific sub-systems applied works at geographic scales  how the tools are applied  

What are Spatial Data? Scale of Data Local Global Information about a specific area, location data. Spatial data types include feature classes, shapefiles, coverages, grids, rasters, images, surfaces or event tables. Scale of Data Local Global

Attributes Features Records

Continuous (grid, raster) vs. discrete (vector) spatial data Grain/minimum mapping unit vs. extent

Continuous Features: Elevation Rainfall Population Landcover Raster Vector Continuous Features: Elevation Rainfall Population Landcover

Discrete Features: Raster Vector Fire Hydrants Cities Sample Sites Point Features Fire Hydrants Cities Sample Sites Line Features Streets Rivers Pipeline Area Features Land Parcels City Limits Census Tracts Lakes

Raster and Vector Combined EGEO-350 Fall 2009

Spatial Scale Extent

Spatial Scale Grain Fine Grained Coarse Grained The minimum resolution of the data. In raster lattice data, the cell size; in field sample data, the plot size; in imagery, the pixel size; in vector GIS data, the minimum mapping unit. Fine Grained Coarse Grained

What Can A GIS Do? Location Patterns and Relationships Areal Measurements Trends Neighborhood Analysis Modeling Queries

Location Where is Feature X? What exists at a specific location? East E.g., What feature is at 5 units South, 11 units East? East 9 10 11 12 13 3 X 3 South 4 4 Z 5 Y 5 9 10 11 12 13

Areal Measurements 5 Km X Y Distance Perimeter Area/Size 30 Km 10 Km2

Patterns and Relationships Does Feature X occur in a pattern? Yes, in a line from NW to SE. Is there a relationship between X and Y? Yes. Y is always close to X. Z X Z Y X Y Y Z X Z

Patterns and Relationships What other spatial or functional patterns exist? Feature Z is always near a border and increases in size from west to east. Z X Z Y X Y Y Z X Z

Neighborhood Analysis Adjacency B is adjacent to A C is adjacent to B C is not adjacent to A Connectivity B is connected to A C is not connected Proximity B is within 2 Km of C A B C A B C 2 Km A B C

Trends How did items A, B, C, and D change from 1980 to 1990? A C A increased size B decreased size; moved C changed shape D Showed-up 1980 1990 B A A B C C D

Modeling Generalization Model Rice Cane Fruit Pine Bare Brush Mix Agriculture Vegetation

Modeling Reality: Model: Sea 4 mountain ranges Rivers drain shortest path to Deep Blue Sea Central Mountains control path of longest stream Other streams drain into it Model: Simplification Generalized reality West Mts. North Mts. Mts. Mts. Central Mts. Mts. East Mts. Deep Blue Sea Mts. Sea

Modeling What-if scenarios: Major stream takes long route around mountain range. Other streams feed directly into it and are very short. New mountain position. Major stream takes short route to ocean. Other streams are longer. One rerouted to secondary stream. Mts. Mts. Mts. Mts. Mts. Mts. Mts. Mts. Sea Sea

ArcGIS Can Employ Many Types of Data Shapefiles Coverages CAD Grids Images Geodatabases Feature classes Tables Rasters

A Shapefile Consists of Many Files Each SHAPEFILE consists of at least three files: Streets.shp Streets.dbf Streets.shx These are the three you will see with all shapefiles, but can include: .sbn, .shn, .met, .avl, .prj files... You need all of the associated files to use in ArcGIS

Coverages and GRIDS Consists of Folders Each Coverage consists of two folders. A folder that has the name of the file and an Info folder.

GEODATABASES ArcGIS Relational Database Management Systems ‘File Geodatabase’ or ‘Personal Geodatabase’ Shell ‘Data Model’ or a ‘Schema’ – A logical construct for the storage and retrieval of data. It’s how the GIS organizes within a database, the data we use for analysis. ArcGIS Geodatabase Exportable Macro Language (XML files)

Important Aspects of RDBMS Data definition language Data dictionary Quality Control Updates Metdata Query Relational Not Excel Interoperable

Queries -- Attribute Data Attribute description What are the attributes of record 2? Where do certain conditions exist? Who owns property with high soil fertility? (Field) - Homer and Flanders

Example of a Complex Query Relational Database Example of a Complex Query Site Suitability (set of conditions) Which property has: Area: > 40,000 Ha Owner: Not Flanders Tax code: B Soil quality: High 1 3 6 2 4 5

Relational Database Stand Table Potential Vegetation Table Landform/Topography Table

Why Do Images Have an Associated World File? The most common image formats are: .Tiff or .tif .jpg or jpeg For an image to be read into ArcGIS, and used with other layers it must have an world file. World Files .tfw (For Tiff or Tif) .jpgw or jpeg (For jpg or jpeg)

Why do files have Different Appearances in ArcCatalog vs Windows Explorer?

Why is it Better to Use ArcCatalog to Move GIS Files?

ArcMap works from Project Files (*.mxd documents) Mxd documents are the ArcMap project files. Mxd stands for (multi-xml documents). ArcMap stores the path and working properties of the data files in a project file (.mxd). This makes it important to keep your data with your ArcMap file (.mxd file).

This is what the .MXD file looks like.. The .mxd stores the path to the datafile

Things to Keep in Mind for Your Own GIS Projects (.mxd) Create a data manage system to organize and store your data files for efficient retrieval and analysis! Keep your .mxd file within your data management system! Before saving in ArcMap, go to File Properties and check on the store relative paths checkmark! Move the entire folder to someplace you will have access later (U:drive or Thumb Drive) Do not rely on things in the C:/temp Drive, it does get deleted.