CIVE 201 Lecture Vector Analysis Lecture, Spring 2015

ArcGIS 4/22/2014 CIVE 220 A 1 Vector Analysis in ArcGIS Vector GIS Analysis • There are multiple ways of conducting geoprocessing in ArcGIS: – Tools � � � � Dialog Box ArcGIS 4/22/2014 CIVE 220 A 2 Vector GIS Analysis • There are multiple ways of conducting geoprocessing in ArcGIS: – Command Line Vector GIS Analysis • There are multiple ways of conducting geoprocessing in ArcGIS: – Script ArcGIS 4/22/2014 CIVE 220 A 3 Vector GIS Analysis • There are multiple ways of conducting geoprocessing in ArcGIS: – Model builder Vector GIS Analysis Process Spatial Data Layer 1 Spatial Data Layer 2 Function 4 Spatial Data layer 6 Spatial Data Layer 1 Function 1 Spatial Data Layer 2 Function2 Spatial Data Layer 4 Function3 Spatial Data Layer 5 ArcGIS 4/22/2014 CIVE 220 A 4 Geospatial Analysis: Features • We will be working primarily with the Analysis toolbox • It is a suite of geoprocessing tools used to solve spatial or statistical problems • Four sub-toolsets: – Extract – Overlay – Proximity – Statistics The Extract Toolset • Contains tools used to manipulate data so that they contain only desired features and attributes � � � � Filtering spatially and/or by attribute ArcGIS 4/22/2014 CIVE 220 A 5 Clip • Clip used for extracting features or parts of features from a feature class • This tool uses a polygon boundary to cut features and their attributes from a feature class • The output feature class will have the attributes of the input features • The input features may be of any geometry type, but clip features must have polygon geometry Clip • If your cookie cutter includes many polygons what will happen? – It will take the first polygon according to ID ArcGIS 4/22/2014 CIVE 220 A 6 Clip: An Example • I have the road network of Lebanon and I just want to select the roads in the Beirut Mohafaza – What is my Input Feature? – What is my Clip Feature? – What is my Output Feature? – What Attributes will my Output have? • It is “Cookie cutting” of one layer using another layer How close the vertices have to be to included in the clip ArcGIS 4/22/2014 CIVE 220 A 7 Split • Breaks the input features and stores them in multiple output datasets • This tool breaks the features into multiple features • The boundary of each unique value in the Split Field is used to split the Input Features • The Split Features must be polygon(s) • The feature attribute table for output � same as the Input Features attribute table ArcGIS 4/22/2014 CIVE 220 A 8 Split • The split field data type must be of type character • The output feature classes will be named for the split field values � They must start with a valid character • The number of output feature classes equals the total number of unique values in the split field Split: An Example • I have the road network of Lebanon and I want to split the roads by Mohafaza – What is my Input Feature? – What is my Split Feature? – What type of files will I generate? – How many files will I generate? – Can I name each layer directly? – What attributes will my outputs have? ArcGIS 4/22/2014 CIVE 220 A 9 ArcGIS 4/22/2014 CIVE 220 A 10 Select • Extracts selected features from an input feature class or layer and stores them in the output feature class based on a search criteria SQL based! Similar to Queries in Access • Mathematical operators such as +, -, *, / can also be used in queries • Example: – Searching for large undeveloped properties – I would then use this expression that would find large properties and then restrict those to only properties that are undeveloped. • [acres]>= 10 AND [property] =“Undeveloped” ArcGIS 4/22/2014 CIVE 220 A 11 Select: An Example • I have the road network of Lebanon and I want to select only the roads that can be classified as “International-Dual” � � � � Select by attribute! – What is my Input Feature? – How many files will I generate? – What Attributes will my outputs have? ArcGIS 4/22/2014 CIVE 220 A 12 Select By Attribute • You can use the “Select by Attribute” from the Select menu in ArcGIS – It does the selection – Does not create a new file directly from your selection ArcGIS 4/22/2014 CIVE 220 A 13 Overlay Toolset • Contains tools for topological integration of features based on symmetry • Has many tools: – Erase – Identify – Intersect – Spatial Join – Symmetrical Difference – Union – Update Erase • Erase: creates a feature class from those features or portions of features outside the erase feature class • Input feature polygons that are coincident with erase feature polygons will be removed • The erase features must be polygons ArcGIS 4/22/2014 CIVE 220 A 14 Erase: An Example • Let us assume that I want to keep all the roads except for the roads in Beirut – What is my Input Feature? – What is my Erase Feature? – How many files will I generate? – What Attributes will my output have? ArcGIS 4/22/2014 CIVE 220 A 15 Intersect • Intersect: builds a new feature class from the intersecting features common in both feature classes • The input features can be point, multipoint, line, or polygon • If the inputs have different geometry types � the output feature class geometry type will default to the same as the input features with the lowest dimension geometry! ArcGIS 4/22/2014 CIVE 220 A 16 ArcGIS 4/22/2014 CIVE 220 A 17 Intersect: An Example • Somehow similar to Identify? • But allows me to intersect multiple layers (>2) at once and the layers NEED NOT be of the same geometry! Union • Union: builds a new feature class by combining the features and attributes of each feature class • All input feature classes and feature layers must have polygon geometry • Can have more than 2 features at the same time ArcGIS 4/22/2014 CIVE 220 A 18 Union Polygons only A list of Polygons Union: An Example • Let us assume I have a project that stretches over Beirut and Mount Lebanon • I want to combine the two shapefiles into one file • Attribute Information from which layer? ArcGIS 4/22/2014 CIVE 220 A 19 Image source: ESRI Arc Info electronic help ArcGIS 4/22/2014 CIVE 220 A 20 Union vs. Intersection • Union is the union of two overlapping set of features and intersection is the intersection Layer 1 + Layer 2 Intersect: “1 AND 2” “1 OR 2” Union: Layer 2 Layer 1 + Union vs. Intersection: Example • Here’s an example. Say we have one layer that shows us where the forest cover (1) is and another that shows us the location of government owned land (2) 2 1 ArcGIS 4/22/2014 CIVE 220 A 21 Union vs. Intersection: Example • Union gives us land that is EITHER forested OR that is a government owned Union vs. Intersection: Example • Intersect gives us land that is BOTH, and preserves all polygon boundaries within that common extent ArcGIS 4/22/2014 CIVE 220 A 22 Identity • Identity: Intersects two feature classes • The output contains ALL the input features as well as those overlapping features of the identity feature class – The order of the layers makes a difference! • The input features can be a point, multipoint, line, or polygon • The identity feature must be polygon Identity • Identity performs an intersection but doesn’t retain ALL features – Keeps all “input” layer features – Keeps/creates only overlapping “identity” features and their attributes Kept, as with union Common (intersecting) areas Not kept, as with intersect ArcGIS 4/22/2014 CIVE 220 A 23 Identify: An Example • Somehow in between a Union and an Intersection ArcGIS 4/22/2014 CIVE 220 A 24 Clip Identify Symmetrical Difference • The opposite of intersection: Removes the areas in common and keeps the features that do not overlap • Uses the boolean operation of XOR • Like Union, layers have to be of the same type ArcGIS 4/22/2014 CIVE 220 A 25 Proximity Toolset • Helps answer one of the most basic questions asked of a GIS – “What's near what?“ • For example: – How close is this well to the landfill? – Do any roads pass within 1,000 meters of a stream? – What is the distance between two locations? – What is the nearest or farthest building from the epicenter of an earthquake? – What is the distance between each feature in a layer and the features in another layer? – What is the shortest street network route from some location to another? Proximity Toolset • Has many tools: – Buffer – Multiple Ring Buffer – Point Distance – Near – Generate Near table – Create Thiessen Polygons ArcGIS 4/22/2014 CIVE 220 A 26 Buffer • Creates buffer polygons around input features to a specified distance • Input can be point, line, or polygon • Output is always a polygon • Distance: – The distance can be specified by the user – The distance can be specified in the attribute table � variable buffer distance Buffer ArcGIS 4/22/2014 CIVE 220 A 27 Buffers • Buffers are great for determining areas of influence • It will create: – Circular regions around your points – Corridors around your lines – Wider regions around your polygons Buffering a Point R= � − �1 � + � − �1 � ArcGIS 4/22/2014 CIVE 220 A 28 Buffering a Line Offsets created around the input line feature Buffer derived from the offsets Buffering a Line ArcGIS 4/22/2014 CIVE 220 A 29 Street Study - Polygon buffer created 2 Km around selected streets Line Buffer Example Buffering a Polygon ArcGIS 4/22/2014 CIVE 220 A 30 Point Buffer Example • Polluting company buffers – Added schools – Added population GIS TUTORIAL 1 - Basic Workbook 74 Polygon buffer 20’ around lights in a parking lot Campus Safety ArcGIS 4/22/2014 CIVE 220 A 31 Line buffer example • Businesses within .25 miles of a selected street 76 GIS TUTORIAL 1 - Basic Workbook Access to public transportation - Polygon buffer created around Bus Routes - Shows areas within 15 minute walking distance from routes Line Buffer Example ArcGIS 4/22/2014 CIVE 220 A 32 Example of Polygon Buffer Polluting Companies within a 500m buffer of a River Fixed line Variable distance (field) What kind of a buffer? FULL: buffers will be generated on both sides. This is the default. LEFT: For line input features, buffers will be generated on the left of the line. This option is not valid for polygon input features RIGHT: For line input features, buffers will be generated on the right of the line. This option is not valid for polygon input features OUTSIDE_ONLY: For polygon, buffers will be generated only outside the input polygon (the area inside the input polygon will be erased from the output buffer) ArcGIS 4/22/2014 CIVE 220 A 33 Example: Variable Width Buffering Noise affected area as a function of traffic flow Fixed line Variable distance (field) What kind of a buffer? FULL: buffers will be generated on both sides. This is the default. LEFT: For line input features, buffers will be generated on the left of the line. This option is not valid for polygon input features RIGHT: For line input features, buffers will be generated on the right of the line. This option is not valid for polygon input features OUTSIDE_ONLY: For polygon, buffers will be generated only outside the input polygon (the area inside the input polygon will be erased from the output buffer) How can I get the inside of a polygon? ArcGIS 4/22/2014 CIVE 220 A 34 NONE: An individual buffer for each feature is maintained, regardless of overlap. This is the default ALL: All buffers are dissolved together into a single feature, removing any overlap LIST: Any buffers sharing attribute values in the listed fields (carried over from the input features) are dissolved Not dissolved Dissolved ArcGIS 4/22/2014 CIVE 220 A 35 Multiple Buffers • Creates multiple ring buffers at specified distances around the input features • These buffers can optionally be merged and dissolved Add your distances here Specify the unit here Specify the name of the field that will hold the distance of the buffer ArcGIS 4/22/2014 CIVE 220 A 36 Example • Areas affected if I have a blast at the Dora Petroleum Hub – 1 tank – 2 tanks – 3 tanks Example • Buffering around a river in case of a flood – Different flood intensities � different flood maps ArcGIS 4/22/2014 CIVE 220 A 37 Near • For each feature in the Input Layer, the Near tool finds the nearest feature in same or other layer(s) • Adds attributes such as distance to attributes of the input table � You DO NOT create a new file • Works with points, lines, and polygons • There can be one or more entries of near features • You can specify a search radius Location if checked will save the X and Y of the nearest feature Angle if checked will save the angle to the nearest feature ArcGIS 4/22/2014 CIVE 220 A 38 Near Point Distance • Works ONLY with point layers • For each point in the input layer, this tool finds the distance to EVERY OTHER point in the same or in another point layer • Results are recorded in a new table • To limit the number of calculations, using a Search Radius is recommended for large datasets because the output table can get really BIG! ArcGIS 4/22/2014 CIVE 220 A 39 Point Distance ArcGIS 4/22/2014 CIVE 220 A 40 Create Thiessen Polygons • Creates Thiessen polygons from point input features • Each Thiessen polygon contains only a single point input feature • Any location within a Thiessen polygon is closer to its associated point than to any other point input feature • Used a lot to assign monitoring stations (e.g. weather stations)