Lab 5

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Lab 5 Information

The purpose of this lab was to create a magazine page with three maps, demonstrating the difference between 2-meter resolution LiDAR, 5-meter resolution autocorrelated, and 10-meter resolution National Elevation Dataset (NED) elevation data at a fine scale, at the same locations.

To do this, I first selected a location that had all three data types available, and settled on Gunnison Island, Utah, which, unsurprisingly is also one of my study sites for American white pelicans. I then downloaded elevation rasters of the three different data types. The LiDAR and the autocorrelated data were downloaded from UT AGRC (under the Elevation/Terrain tile), while the NED data were from the USGS (National Map site). The 2-meter scale rasters were small, and I had to download two of them to cover the entire island, while the other two data types had single rasters available that covered the entire island.

Once downloaded, I imported the rasters into ArcMap, and checked the coordinate systems. Two were correctly projected as NAD 1983 UTM Zone 12N, but the 10-meter raster had to be projected using the "Define Projection" tool. I also had to stitch together the 2-meter rasters using the "Mosaic to New Raster" tool, because the 2-meter data was broken into two rasters, but the other rasters were fine as is.

After this, I created three new layers from each dataset: hillshade, slope, and aspect. I used the batch processing option to create hillshades from each raster using the "Hillshade" tool, then did the same with slope by batch processing with the "Slope" tool, and finally aspect with batch processing using the "Aspect" tool. This created a total of nine new layers for my map. From there, I created new data frames within my map and sorted the raster layers into their respective resolution categories, and then added each data frame to a new map layout as a separate map. I fixed the 5-meter and 10-meter map windows to the extent and area visualized in the 2-meter window by fixing their extent to "Other Data Frame" and specifying the margins to 100 so they all matched.

Then, to correct symbology discrepancies between each map because of the differences in elevation resolution, I chose a nice color ramp in the Symbology window for the 2-meter dataset, and set the stretch type to "Minimum-Maximum". I repeated this for the other two datasets and then edited the high and low values boxes for the 5-meter and 10-meter datasets to match the 2-meter values. Finally, I set the transparency on the DEM to 35% to allow the hillshade layer to show through.

To complete the magazine page, I added text telling about each map and the focal area, added pertinent information like data source and author, and added a legend and scale bar. The finished page was exported as a .png and .pdf file.

These maps could be improved with coordinates of the island, and perhaps a reference map to indicate where Gunnison Island is within the Great Salt Lake, especially for those not familiar with the area. Also, autocorrelated data without the anomalies or drawing errors would be helpful to show the resolution difference in the three datasets, although I feel like the issues with the autocorrelated data I encountered show nicely what they mean when they say the autocorrelated method is not as rigorous as the other two methods.

Additional Downloads

High resolution (PDF) download available here