lab8_raster_sufaces

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University Of Arizona *

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420

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Anthropology

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Feb 20, 2024

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GIST 420 Raster Surface Creation Y our GIS lab been contracted to perform some analysis for an archaeologist. Specifically, you will try to find out if there is a relationship between archaeological sites and local terrain . An archaeologist friend has sent you data in a variety of file formats and today you will explore some of the data and create a couple of interpolated surfaces. These surfaces will be the first component of an investigation of the relationship between sites and terrain. There is a “l ab_8 ” directory in the file server for this course and you will need to copy this directory into your user area. Here, you will find an ArcGIS Project folder containing a file geodatabase comprising several feature classes and a couple of rasters from the Tall Hesban region on the Madaba Plain, in Jordan. Tools In order to complete your tasks, you will need to use geoprocessing tools in the Toolbox . Here is a short list of tools you might find helpful for your work. Remember to try to work through the help files before you ask for assistance. Processing Steps We have organized the lab around four tasks: initial data investigation, surface creation, surface comparison and interpretation. Please note that in the following processing steps, there are also questions in bold . These questions are to help you think through the processes of the lab and prepare you for the interpretive section at the end of the lab. Please do not submit answers to these questions, but do make notes . Lab Setup 1. In the Windows file explorer navigate to the “lab_8 \Raster_Surfaces ” folder and, once there, open the “ Raster_Surfaces ” project by double- clicking on its name (Raster_Surfaces.aprx) in the explorer. Note the organization of the data in the geodatabase. Initial Investigation 2. Rename the existing map ( “ Map ” ) to “ Raster Interpolation ”. 3. Find the Geoprocessing Environment dialog (Analysis Ribbon > Environments) and set the processing extent and the snap raster to “ hdem ” and the raster analysis mask to “ Survey_Area ” . Be sure you are using the rasters and feature classes in the geodatabase for this step. Spatial Autocorrelation IDW Spline Summary Statistics Raster Calculator

Gary L. Christopherson, RNR 420 – lab 8 – Updated 3/31/2018 (CAW March 2022) 2 4. Check out these data by adding some of the feature classes to the map canvas and exploring feature symbolization. Look at the tables to find out what data are attached to the features. Note specifically the table for the pottery sample locations. One of the attributes is for total weight of pottery. How might these weights reflect ancient settlement in the area? 5. From the Symbology pane, symbolize pottery_sample using proportional symbols with TOTWGHT. Looking at the distribution of these symbols, in very general directional terms, where do you think most of people lived in antiquity? 6. Measure the degree of global spatial autocorrelation in the pottery weights. Use the Spatial Autocorrelation tool from the Analyzing Patterns toolset of the Spatial Statistics toolbox to measure the spatial autocorrelation and create a graphic report for you. The Input Feature Class will be “pottery_sample” and the input field will be “TOTWGHT”. Accept other defaults. Be sure to check the box to generate a report. You can access the report as an html file from a link in the tool processing message when it completes. Seems to work better in Chrome browser. What does the Moran’s Index value, z -score and p-value indicate about the pottery weight pattern (if any)? Surface Creation 7. Find the Inverse Distance Weighted (IDW) tool in the Interpolation toolset of the Spatial Analyst tools and use it to create a raster surface based on the pottery weights in the pottery_sample feature class. Set the power to 2, the search radius to variable, the number of points to 12, and the cell size to that of hdem, which is 20. Name this raster “ idw2_pottery ” and save it in your geodatabase . 8. Display your new raster by stretching it and selecting a color ramp that you like. According to this surface, where were the largest amounts of pottery found? 9. Make a second IDW surface, called “ idw10_pottery ” , using the IDW tool. Keep all the parameters the same as those above except for power, which you should set to 10 . Display it by stretching it and using the same color ramp as the previous step. What was the effect of changing the power to 10? 10. Use the same “ pottery_sample ” feature class as input to create a splined surface. Start the SPLINE tool from the Spatial Analyst tools . Name the output raster “ spline1_pottery ” , and set the spline type to regularized, the weight to 0.1, the cell size to that of hdem and the number of points to 12. Display the results by stretching the values and using the same color ramp. 11. Based on the vector and the raster data, where was most of the pottery/human settlement located in the Tall Hesban region?

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