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Isarithmic Mapping

 

Map 1: Annual Precipitation, Washington State

Map 1 is an Isarithmic map that follows the continuous phenomenon of rainfall in Washington state over a 30 year period. The data was created by the PRISM group at the Oregon State University in 2006, and then downloaded and amended by the U.S. Department of Agriculture, Natural Resources Conservation Service, National Geospatial Management Center in 2012. Eden Santiago Gomez, analyzed the data on 5/2/2021, to create the map above. Santiago Gomez created continuous tones for the data, also adding a hillshade effect. She then converted the floating raster data into Integer data via the geoprocessing tool Int (Spatial Analyst Tool) to bring out hypsometric tinting. Lastly, she added contours of the data via the Contour List tool.  

How the precipitation data was derived and interpolated?

The PRISM system has been continually developed over the past couple decades, utilizing physiographical maps and climate fingerprints as its method of interpolation. Climate fingerprints uses the assumption that “that patterns in climate caused by the earth’s physiography tend to be repeatable over time,” which then can be used to create a regression model in PRISM for interpolation. (Daly, Bryant 2013) Allowing us to create maps of the past and present where there might be gaps in the data or possibly incorrect data. PRISM uses a climate-elevation regression, by incorporating elevation into the surface of the map through a digital elevation model (DEM). (Module 6 Lab Instructions)

a)     What does continuous tone symbology mean and how was it implemented in the map?

Continuous tone symbology represents continuous data. This is usually raster data with not just x and y location, but also z (ex: elevation) that represents the magnitude of x,y. Continuous data is also non discrete as it is surface data. On a map, this data uses continuous tone symbology to represent it. This is done by contour lines and sometimes hillshade shading. A contour line, is a line through all the contiguous points of y. Hillshade shading is the 3D representation of the surface of the relative data. This can be incorporated through DEM. 



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