Determine the surface area and the volume of the ring formed by rotating the square about the vertical axis.
Overlay ◦ Union Keep the spatial coverage from all input layers ◦ Intersect Only keep the overlap area ◦ Clip Intersect Union Clip 1 Overlay ◦ Union Keep the attributes info from all input layers ◦ Intersect ◦ Clip Only keep the attributes info from the layer to be clipped 2 Buffer Fixed Distance Varied distance from an attribute field Simple buffer – overlap dissolved 3 Dissolve – aggregate features based on specific attributes. One row in attribute table Dissolve function doesn’t consider spatial adjacency: Result: multipart polygon (or feature) 4 True/False In a buffer analysis, you can apply different buffer distances to the features in a same polygon shapefile. ◦ True The distance can be fixed, or be read from the attribute table. Overlay analysis is only applicable to polygon layers. ◦ False 5 Which of the following vector based GIS analysis keeps the common spatial area from both input layers, but only keep the attribute value from one input layer A. Union B. Intersect C. Clip D. Overlay 6 You can use the same clipping tool to clip vector and raster layers. Clip Raster Clip Vector 7 Dissolve function aggregates features based on the same value combinations and spatial adjacency. Based on spatial attribute only! Include: A single attribute Attribute combination 8 Study area: Define your study area. If the boundary file doesn’t exist, create one and digitize the boundary. Lab 4, Lab 5, Lab Quiz 3. Coordinate System: Define your layer coordinate system. Important for part 2 of the project. – Check with Teaching Assistants if you need help. Some of you have worked on part 2. Still need a new submission of part 2. 9 Part 1: ◦ Data Layers: Roads Streams Lakes and other water bodies Ortho DEM ◦ Optional: Soils, rails, land user, other 10 Part 2: GIS analysis ◦ Select at least 3 analysis Query (select by attribute or location) & Export Data Buffer Overlay (clip, or union, or intersect) Create & edit data (create new vector layer, or georectification) Terrain modeling (slope, aspect, hillshade, and viewshed) Raster calculator Reclassification Spatial interpolation 11 Due Friday, 3:30 pm, April 22, 2016. Report: submit to blackboard – for each analysis ◦ Spatial question, purpose of analysis ◦ Detailed analysis steps ◦ Maps & tables of your analysis results ◦ Conclusion ◦ Reference & Acknowledgement Data on N drive: ProjectPart2.mxd Start Early! 12 Query Field Statistics Review lab in week 8. 13 Terrain Analysis 14 Raster consists of a matrix of cells (or pixels) organized into rows and columns where each cell contains a value representing information. 15 Each cell consists of the same width and height. The dimension of the cells can be as large or as small as needed. The size determines how coarse or fine the patterns of features in the raster will appear. 16 Raster datasets with continues values don’t have attribute table. Raster with categorical values, or integer values can have associated attribute value. 17 DEM – Digital Elevation Model T errain determines the natural availability and location of surface water, and hence soil moisture and drainage. T errain defines watershed boundaries and hydrologic networks. 18 When you add your raster dataset into ArcMap, there are times that ArcMap asking if you want to generate pyramid. Pyramids are reduced-resolution representations of your dataset and are used to improve performance. Pyramids can speed up display of raster data by retrieving only the data at a specified resolution required for the display. Pyramids are created by resampling the original data. Reading your source tab in properties dialog box: Adjust the symbology Most often used Variable Description Importance Height Elevation above base Temperature, vegetation, visibility Slope Rise relative to Water flow, erosion, travel cost, horizontal distance construction suitability, habitat suitability, geology Aspect Downhill direction of Temperature, vegetation, steepest slope moisture, insolation Contours Lines that connect Shows how values change across locations of equal a surface elevation Hillshade Shaded relief from DEM Visual effect, background overlay by considering the illumination source angle and shadows 22 In ArcMap, you will need extensions to work with these terrain variables. 23 Slope is defined as the change of elevation ( a ris) with a change in horizontal position ( a run). Slope is often reported in degrees ( 0° is flat, 90° is ve)tical Sometimes, slope is also reported in percent. Horizontal and Vertical Measurements must be in the same units. Don't use USGS DEM data that has horizontal units in decimal seconds with slope, hillshade, visibility, and curvature. Project it into a planar coordinate system before using any of the above functions. Z-factor is the essential parameter in terrain variables calculation. Definition: Number of ground x,y units in one surface z unit Z-value: hight Z-value * Z-factor -> same measurement unit as XY Example: If your z units are feet and your x,y units are meters, you would use a z-factor of 0.3048 to convert your z units from feet to meters (1 foot = 0.3048 meter). If XY units are decimal degrees, and z-unit are meters: Inclination of slope As % rise or in degrees Using a 3 by 3 moving window Measured in the steepest direction of elevation change Often does not fall parallel to the raster rows or columns The orientation of a slope Aspect may be reported as an azimuth angle, measured clockwise in degrees from north. Identify which locations have the same value. A useful surface representation. The hypothetical illumination of a surface by determining illumination values for each cell in a raster. It can greatly enhance the visualization of a surface for analysis or graphical display, especially when using transparency. Azimuth (angle of the light source = 315° Altitude angle of the light source above the horizon = 45° Azimuth = 180° Altitude = 30° Azimuth = 135° Azimuth = 135° Azimuth = 45° Altitude = 80° Altitude = 45° Altitude = 45° Parameters: Altitude Azimuth Default sun altitude for hillshade is 45º Default sun azimuth (direction) for hillshade is 315º A viewshed identifies the cells in an input raster that can be seen from one or more observation locations. Input: DEM + observer points feature class (points or lines) The nodes and vertices of lines will be used as observation points. Output: Each cell in the output raster receives a value that indicates how many observer points can be seen from each location. All cells that cannot see the observer point are given a value of 0. Examples: Which areas can be seen from a fire lookout tower that is 15 meters high From which locations on the landscape will an ancient fortress be visible How frequently can a proposed disposal site be seen from an existing highway Hydrology toolset: Flow direction Flow accumulation Stream Network Watershed boundary Reclassify tool allows you to reclassify or change input cell values to alternative values. Most common reasons for reclassifying data: Group certain values together Reclassify values to a common scale Replace values based on new information Set specific values to NoData or set NoData cells to a value 40 41