Presentation on theme: "NPS Introduction to GIS: Lecture 1"— Presentation transcript:
1 NPS Introduction to GIS: Lecture 1 Based on NIMC and Other Sources
2 Lesson Objectives Understand what a GIS is Understand how a GIS functionsUnderstand how spatial data isrepresented in a GISLook at some GIS applications
3 Data vs. Information Data, by itself, generally differs from Data is of little use unless it is transformedinto information.Information is an answer to a questionbased on raw data.We transform data into informationthrough the use of an Information System.
5 What is an Information System? SYSTEM USED FOR:capturingstoringupdatingAn information system is designed to efficiently capture, store, update, manipulate, analyze, and display DATA.Remember: Data is NOT InformationmanipulatinganalyzingDATA
6 What is an Information System? Data StorageInformation SystemInformationQueryInformation systems can be very simple, such as a telephone directory.This slide gives a simple illustration of how we extract information. A very basic example of an information system is a telephone book. It stores data, but if we pose a question such as “What is John Doe’s phone number?” we can find the answer. However, this information system is limited because if we pose a different question such as “Whose phone number is ?”, we can not easily obtain the answer.
7 What is an Information System? In the digital environment we use software to create complex information systems.DatabaseSome software is optimized for manipulating databases. MS Access is an example of this. Modern database management programs utilize a relational database. This is a database that references each piece of information once and then keeps track of the relationships among them. In this wayManagement
8 What is a GIS? + Information System A means of storing, retrieving, sorting,and comparingspatial datato support someanalytic process.+Geographic PositionA GIS can be best defined by defining the two parts of the term; geography and information system.Geography is a science that deals with the earth and life on the earth, while an information system is a way to capture, store, retrieve, sort, and process data to support some analytic process.
9 GEOGRAPHIC Information System What is a GIS?GEOGRAPHIC Information SystemWhat makes the Information System geographic?The user needs to begin spatially!GIS links graphical features (entities) to tabular data (attributes)
10 GIS DefinitionA GIS is a system (hardware + database engine) that is designed to efficiently, assemble, store, update, analyze, manipulate, and display geographically referenced information (data identified by their locations).A GIS also includes the people operating the system and the data that go into the system.A geographic information system (GIS) is a computer-based tool for mappingand analyzing things that exist and events that happen on Earth. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps. These abilities distinguish GIS from other information systems and make it valuable to a wide range of public, military and private enterprises for explaining events, predicting outcomes, and planning strategies. Whether siting a military base camp, finding the best soil for a tank to maneuver on, or figuring out the best low level air route for a bombing raid. Map making and geographic analysis are not new, but a GIS performs these tasks better and faster than do the old manual methods. And, before GIS technology, only a few people had the skills necessary to use geographic information to help with decision making and problem solving. Today, GIS is a multi-billion-dollar industry employing hundreds of thousands of people worldwide. GIS is taught in schools, colleges, and universities throughout the world. Professionals in every field are increasingly aware of the advantages of thinking and working geographically.
11 Key Functions of a GIS Data can be: Positioned by its known spatial coordinates.Input and organized (generally in layers).Stored and retrieved.Analyzed (usually via a Relational DBMS).Modified and displayedA geographic information system (GIS) is a computer-based tool for mappingand analyzing things that exist and events that happen on Earth. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps. These abilities distinguish GIS from other information systems and make it valuable to a wide range of public, military and private enterprises for explaining events, predicting outcomes, and planning strategies. Whether siting a military base camp, finding the best soil for a tank to maneuver on, or figuring out the best low level air route for a bombing raid. Map making and geographic analysis are not new, but a GIS performs these tasks better and faster than do the old manual methods. And, before GIS technology, only a few people had the skills necessary to use geographic information to help with decision making and problem solving. Today, GIS is a multi-billion-dollar industry employing hundreds of thousands of people worldwide. GIS is taught in schools, colleges, and universities throughout the world. Professionals in every field are increasingly aware of the advantages of thinking and working geographically.
12 Geographic Information Systems DecisionGISProcessOutputGIS analysisImport or build datasetsDefine GIS criteriaDefine problemDefine problemDecisionGISProcessDefine GIS criteriaOutputGIS PROCESS:The GIS process involves six steps that are common to what we refer to as the end to end map-making process.1. Define the spatial problem/question..Define the GIS criteria..Import or create the data sets.Perform the GIS analysis.Create the output.Decide whether or not the output solves or answers the spatial problem/question. If not, then refine the problem and start the process again.GIS analysisImport or build datasets
13 MODELLING AND STRUCTURING DATA (How we represent features or spatial elements)
14 Representing Spatial Elements RASTERVECTORReal WorldSpatial data is essentially data with a location. It contains information about the location and shape of, and relationship among geographic features usually stored as coordinates. Spatial data comes in two types, VECTOR and RASTER. Geographic information systems work with two fundamentally different types of geographic models--the "vector model" and the "raster model."
15 Representing Spatial Elements RasterStores images as rows and columns of numbers with a Digital Value/Number (DN) for each cell.Units are usually represented as square grid cells that are uniform in size.Data is classified as “continuous” (such as in an image), or “thematic” (where each cell denotes a feature type.Numerous data formats (TIFF, GIF, ERDAS.img etc)A raster image comprises a collection of grid cells rather like a scanned map or picture. Both the vector and raster models for storing geographic data have unique advantages and disadvantages.Raster models do not provide precise locational information because space is divided into discrete grid cells. The assumption is that a point can be found within a grid cell.
16 Representing Spatial Elements VectorAllows user to specify specific spatial locations and assumes that geographic space is continuous, not broken up into discrete grid squaresWe store features as sets of X,Y coordinate pairs.In the vector model, information about points, lines, and polygons is encoded and stored as a collection of x,y coordinates. A single x, y coordinate, can describe the location of a point feature, such as a control tower. Linear features, such as roads and rivers, can be stored as a collection of point coordinates. Two coordinate pairs are enough to show location and orientation in space. Polygonal features, such as an area of operations and lakes, can be stored as a closed loop of coordinates. The vector model is extremely useful for describing discrete features, but less useful for describing continuously varying features such as soil type.Spatial data is unique to a GIS in that there are two aspects two it. It has a location and an attribute. The location can be either a geographic coordinate, MGRS coordinate, or any other (x,y) coordinate. The attribute can be either adjectival (describing the object) or have a magnitude (a numerical value).
17 Entity Representations We typically represent objects in space as three distinct spatial elements:Points - simplest elementLines (arcs) - set of connected pointsPolygons - set of connected linesWe need symbolize spatial features in order to be able to associate attribute information.We can classify different features into different dimensions. Each classification of dimension is a conceptual classification.Points - “0” dimensionality. No length or Width.Each point is Discrete in that it can only occupy a given point in space at any given time.Lines - “1” dimensional. Length, but No Width.Must have a beginning and an ending point.Polygons - “2” dimensional. Length and Width.By adding Width, we can describe a feature as having an area.Surfaces - “3” dimensional. Length, Width, and Height.Surfaces have infinite number of values (e.g. Elevation). We say that this type of data is Continuous.When thinking of spatial elements, we must consider Spatial Scale. Depending on scale, we may want to represent a river as a line or a polygon.We use these three spatial elements to represent real world features and attach locational information to them.
18 AttributesIn the raster data model, the cell value (Digital Number) is the attribute. Examples: brightness, landcover code, SST, etc.For vector data, attribute records are linked to point, line & polygon features. Can store multiple attributes per feature. Vector features are linked to attributes by a unique feature number.
19 Raster vs. Vector Raster Advantages Vector Advantages The most common data formatEasy to perform mathematical and overlay operationsSatellite information is easily incorporatedBetter represents “continuous”- type dataVector AdvantagesIn Raster we explicitly store attribute information and imply its location based on the position within the grid cell structure.In Vector, we explicitly store the entity information and where the entity is located. We rely on a database structure to link to attribute information.Accurate positional information that is best for storing discrete thematic features (e.g., roads, shorelines, sea-bed features.Compact data storage requirementsCan associate unlimited numbers of attributes with specific features
21 GIS Functions Data Assembly Data Storage Spatial Data Analysis and ManipulationSpatial Data Output
22 GIS Functions Data Assembly Manual Digitizing Manual Digitizing ScanningManual DigitizingScanningRSIMapsIntel DatabaseData TransferData TransferI n p u t: Before geographic data can be used in a GIS, the data must be converted into a suitable digital format. The process of converting data from paper maps into computer files is called digitizing. Modern GIS technology can automate this process fully for large projects using scanning technology; smaller jobs may require some manual digitizing (using a digitizing table). Today many types of geographic data already exist in GIS-compatible formats. NIMA standard digital data exists in useable formats and can usually be loaded directly into a GIS.Direct EntryGPSKeyboard
23 Data Input/CreationThis slide demonstrates heads-up digitizing done in ArcView.
24 GIS Functions Spatial data Attribute data GIS Storage 1 (Universe polygon)Spatial data233(ARC functions)45Storage: For small GIS projects it may be sufficient to store geographic information as simple files. There comes a point, however, when data volumes become large and the number of data users becomes more than a few, that it is best to use a database There are many different designs of DBMSs, but in GIS the relational design has been the most useful. A DBMS is nothing more than computer software for managing a database--an integrated collection of data. In the relational design, data are stored conceptually as a collection of tables. Common fields in different tables are used to link them together. This surprisingly simple design has been so widely used primarily because of its flexibility and very wide deployment in applications both within and without GIS.COV# ZONE ZIP12C-1922060Attribute data3A-4220613A-4220614C-2222060(INFO or TABLES functions)5A-522057
25 GIS Functions Spatial Data Manipulation and Analysis Common ManipulationReclassificationMap Projection changesCommon AnalysisBufferingOverlayNetworkAnalysis and M a n i p u l a t i o n: It is likely that data types required for a particular GIS project will need to be transformed or manipulated in some way to make them compatible with your system. For example, geographic information is available at different scales (street centerline files might be available at a scale of 1:100,000; Topographic line maps data such as ITD at 1:50,000). Before this information can be integrated, it must be transformed to the same scale. This could be a temporary transformation for display purposes or a permanent one required for analysis. GIS technology offers many tools for manipulating spatial data and for weeding out unnecessary data.
26 Spatial AnalysisOverlay function creates new “layers” to solve spatial problemsThe overlay operation is one the most powerful functions in a GIS. It gives the user the ability to place the cartographic representation of thematic data over one another.However, this is hardly a new function developed by a GIS, but it has been revolutionized by the use of the computerized GIS.
27 GIS Functions Spatial Data Output Tables Maps Interactive Displays 3-D Perspective ViewThere are many forms of output for a GIS. The first is usually softcopy, namely what you see on the screen. Most Military service member and commanders prefer to have something hardcopy. So more often than not, will require hard copy outputs. A full functioning GIS can do this. It can plot/print given the equipment, the 2D and 3D perspective views on a 2D map.
29 GIS Applications Site selection Helicopter Landing Zones Amphibious Assault (Water Depth)Buffer ZonesFlight PlanningBattlefield VisualisationTalk to each one relevant to the audience.
30 Helicopter Landing Zones HLZ sitesThis slide shows Helicopter Landing Zones within ArcInfo
31 Amphibious Assault Planning Often times to map the ocean floor in terms of elevation we use Bathymetric data or DBTB (Digital Bathymetric Data Base). This slide also shows vector data overlaid on top of the data.
32 Spatial Analysis Proximity Analysis (Buffers) 1000 Meter Buffer of RailroadsThis slide shows a proximity analysis of railroads around the Tuzla airport in Bosnia. The buffer is 1000 meters and the areas in blue represent all areas within this 1000 meter range.CAUTION: DO NOT Make assumptions based on visual correspondence only. The user must obtain evidence on a true cause and effect relationship.
33 Flight PlanningThis slide shows an example of flight planning within ArcView through the use of Elevation and Cloud cover data.
36 Other GIS Applications Cross country movementRoute planningIntervisibility studyFacilities managementAirfield assessmentRoad network analysis (convoys)Propagation coveragesObservation post siting analysisPerspective views
37 CCM AnalysisCCM (Cross Country Movement) Analysis allows the user to model the cost (e.g. time) it would take for a give object to travel from point A to Point B given the difficulty of the terrain.For example, if a tank had to travel from point A to point B and you new how fast it could travel on certain road types, soil types, and slopes, you could model the travel cost.
38 CCM & ViewshedThis slide shows a CCM analysis along with a viewshed analysis. The viewshed analysis is used to illustrate what a person can or can not see from a certain point. The two areas denoted by the purple and turquoise angles illustrate two separate viewsheds. The region of overlap shows the area that can be see by both observers from their respective positions.
39 Facilities Management Facilities Management encompasses a wide range of applications. The examples shown above are:1. Housing Assessments2. Power Line Maintenance and Tracking3. Crime around Schools4. Water lines/pipes Maintenance and Tracking
40 AirfieldsThis slide shows information on Airfields along with a picture/movie that has been hot-linked to the feature.
41 Network AnalysisThe slide shows a Network model, which gives the best route given certain criteria. The green squares denote bridges, which can serve as a limitations within the model. For example, if a bridge was impassible, we could factor that criteria into our model and the route could be recalculated giving us a different solution.