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# GEG 592 Notes GEG592

UM

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This 7 page Class Notes was uploaded by Ricky Reboredo on Wednesday February 4, 2015. The Class Notes belongs to GEG592 at University of Miami taught by Dr. Sen Roy in Fall. Since its upload, it has received 170 views. For similar materials see Intermediate GIS in Geography at University of Miami.

## Reviews for GEG 592 Notes

If you want to pass this class, use these notes. Period. I for sure will!

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Date Created: 02/04/15

GEG 592 Topology Adjacency Shape le has no topology geodatabase does TIGER An early application of topology in geospatial technology It comes from the census Topoogy ensures data quality and enhances GIS analysis Georelational Data Model Shape le Good for visualizations bad for spatial analysis Look up Geoda Object based data model For your nal project presentation put a map of the area nd some relevant literature your objectives lit review end with one or two questions that youre looking for Print it out for everyone LECTURE Spatia Analysis Different types of Analysis that you can do with your data Looking for geographic patterns and relationships between features but spatially Topoogy where objects and phenomena occur where are they on the map GS representation vs Analysis Categories Queries and Reasoning What is happening Why is it happening Measurements Transformations Descriptive Summaries Optimization Hypothesis Testing Visuaization a simple method for gaining information about spatial data l DISPLAYING YOUR RESULTS Spatia Analysis helps gain information from GIS Interpolation You have a set of points and you want to create a continuous surface EX Soil Samples temperature mapping rainfall Estimation of surface values at unsampled points based on known surface values of surrounding points Advantages create continuous surface to do overlay analysis Start with a set of known points similar to TIN models Different types of interpolation Distance and Density analysis Density shows you where things are concentrated Density is with count data interpolation is continuous data Examine coffee shops and their customers using Iocation Errors and Uncertainty Spatia Uncertainty D How do you de ne the boundary of a study area Vagueness How many Oaks to qualify an area as an Oak Woodland Ambiguity Uncertainty Physica Measurement error Digitizing Error Uncertainty in Raster data structure Mix ceIIs de ning categories Uncertainty in Vector data structure administrative boundaries may not always be the best boundaries to use Modifiable Areal Unit Problem The number sizes and shapes of zones affect the results of analysis Distance Rasters Eucidian Distance straight line distance Geometric Transformation Geometric transformation is the process of using a set of control points and transformation equations to register a digitized map a satellite image or an air photograph onto a projected coordinate system Control Points Points that we know the exact location of lmage to map transformation changes the rows and columns of a satellite image into projected coordinates As long as you know the top left corner you can immediately put it on the map Different methods have been proposed for transformation from one coordinate system to another Equiarea preserve everything it39s just a little bit tilted Simiarity Compressing everything the proportion is the same Affine Most common form of geometric transformation basic properties maintained Projective Mostly used for aerial photographs The affine transformation Rotation translation skew scaling Three basic steps Colect Ground Control Points Create equations relating the image pixelmap feature coordinates at those GCPs to their realworld coordinates and transform the pixel coordinates based on the equations Apply the transformation to the entire input imagemap features to output values in the newly georeferenced Root Mean Square Error RMS is a common measure of the goodness of the control points It measures the deviation between the actual and estimated locations of the control points lnterpretation of RMS Errors If an RMS error is within the acceptable range we usually assume that the transformation of the entire map is also acceptable This assumption can be quite wrong however if gross errors are made in digitizing the control points youre screwed mage to map transformation Resampling of Pixel Values Creates a new gridlayer you can give the cell size and you can import all the values from the original layer Resamping Common resampling methods are nearest neighbor bilinear interpolation and cubic convolution Nearest neighbor you take the centroid of the grid and whatever is closest is the value given Does not change any values is appropriate when values must be preserved Biinear interpolation average of the four nearest grid cells are taken into consideration Cubic convolution 16 grid ces instead of four Raster Data Analysis Based on cells and rasters 1015 Different types of models DEM Digital elevation model TIN Triangles Contour Maps digitized from topographic maps You can create contour maps from spacial interpolation methods How to create DEM Created from Spot elevations Why does the density of spot elevations matter The more dense the more accurate the georeferencing lnterpoating a DEM Getting from a set of spot elevations to a DEM requires the use of interpolation lnterpoation creates a continuous eld representation from Discrete objects lnverse Distance Weighting Trianguated Irregular Networks Triange vertices represent certain kinds of terrain features The edge of the triangles represent other terrain features For data sets presentation What is your spatial resolution What is the temporal resolution What time period are you looking at Make a map Give some basic statistics For land use check if there are any outliers Map your land use Why were there outliers why do you think there are outliers Look for basic stats mean median mode Sources of data Do a quality check for your data Why is accra important why is it important to know about this particular city Start with your question then look at your data sets Shes not looking for methods just say what your data set is what your question is It will be a class discussion Think about what you have to do from here This is the second stage of your paper View shed analysis what can I see from here View shed analysis refers to the portion of the land surface that is visible from one or more viewpoints Line of sight operation is the basis for viewshed analysis The line of sight connects the viewpoint and the target Viewsheds can be derived from elevation rasters or TINS Cumuative Viewshed The output of a viewshed analysis is a binary map showing visible and not visible areas Accuracy of Viewshed Analysis The accuracy depends on the accuracy of the surface data the data model and the rule forjudging visibility Watershed Analyis Deaing with topographic features water ow surface water lmportatnt for management and planning agricultural areas etc How do we do watershed analysis Make a lled dem a dem devoid of depressions Derive a ow direction raster which shows the direction water will ow out of each cell For each cell where will the water ow Derive an accumulation raster derive a stream network When youre dealing with temporal data you can look at correlation within the cells then use that as a model ldentify and ll sinks Map your data in histograms or bar graphs Know your data Flow direction evaluates the direction of steepest descent for each cell in the grid by comparing a cell with its eight neighbors Always digitize from upstream to downstream Notes for the semester 2 weeks left We39ll be working on individual projects When we come back from thanksgiving we have 1 more Tuesday left that s the day for nal presentations On the 19th she wants a detailed writeup on the data sets and the revised proposal essentially just the literature review 4 to 5 ish pages 2 for data sets 2 for revised proposals Presentation is on the 10th Least Cost Path Analysis and Network Analysis Path Analysis trying to get from Point A to Point B Google maps least cost path D trying to nd out how much this is going to take Cost can be a measure of time This consists of a cost raster D this de nes the cost of moving through each cell each pixel has a value We come out with something called the least accumulative cost path Optimum path Known origin destination Cost Raster de nes the cost or impedance to me though each cell The cost distance measure is based on the nodelink cell representation Accumulated travel cost distance cost of travel cost can be whatever Least accumulative cost This is commonly used for mapping shortest path Here we use a network a network is topology based each line knows about the existence of the other line If youre trying to go from point a to point b each line needs to know how theyre connected to the other Geometric networks go into arc toolbox build topology You have to let the street network know about itself Network components Links and link impedance Junctions and turn impedance Creating weights if weights do not already exist in the network you cannot use them Closest Facility nds the closest facility such as hospital etc Applications of the MAT Minimum Aggregate Travel Optimizing Point Locations Aocation LocationsAlocation Problems

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