Module 6: Working with Geometries

The purpose of this week's lab was to explore the geometries of a shapefile by writing vertices to a text file. The final script created a new TXT file, used a search cursor to iterate over the rivers shapefile geometries with for loops, and then writing data to the new TXT file. The final TXT file contains the following data from the rivers.shp: feature OID, vertex ID (created in the script), x & y coordinates, and the name of the feature. Below is a screen shot of part of the data in the new TXT file (the full TXT file is not shown as it is very long and contains 0-25 features with a total of 247 vertices).


One of the things that made creating and running this script easy was the use of geometry tokens, specifically OID@ and SHAPE@. Geometry tokens are pieces of code that allow us to interact and access specific information about the geometry of features, which saves time when working with large datasets and/or features with a lot of geometry information.

The only big issue I had  was creating the new TXT file. Simply using the new file name did not create and write to a new TXT file. Instead, I had to include the full file folder path with the name when creating the file. This worked to my advantage as I wanted to save the new file in my Results folder and not the working environment folder, which was the Data folder. Other than the TXT file creation, the main issues were syntax issues which is the same as with every script and new this week was where to use (), [], and {}.

Comments

Post a Comment

Popular posts from this blog

Module 2: Coordinate Systems

Image
In this week's lab I explore different coordinate systems and projections in order to better understand the nature of distortions introduced by the systems. For the last part of the lab, I was tasked with selecting a state in the contiguous US and selecting an appropriate projection for the area. I selected the state of Wyoming as my area of interest. Wyoming has 4 State Plane zones and two UTM zones, so neither a single State Plane nor UTM system would work for this area without distorting the size or shape of the state. Therefore, the best coordinate system for this area is Custom Coordinate system. I chose NAD 1983 WyLam (Meters), a custom system specifically for the state of Wyoming, as the projected coordinate system. This coordinate system is a Lambert secant-case normal-aspect conic type projection which preserves shape and is appropriate for a general reference map. The standard parallels are placed at 41N and 45N, the boundaries of the state of Wyoming, which minimizes...
Read more

Module 6: Proportional Symbol and Bivariate Choropleth Mapping

Image
The objectives of this week's lab was to explore proportional symbol and bivariate choropleth mapping techniques, as well as customizing legends for each technique. One of the data sets for this lab included positive and negative values. The final map utilizes proportional symbols to show both positive and negative values. This map is essentially two proportional symbol maps overlaid on each other, one for positive job growth and another for negative job growth, with the symbols for both variables sized the same. Utilizing proportional symbols to show both positive and negative values is an effective way to visualize areas that show the greatest and lowest values. These areas are easy to see quickly on the map and give the map reader a simple way to visualize the variable being mapped. Fig 1. Proportional symbol map using positive and negative values.  Another data set for this lab examined contained two data variables: percent of the US population in each state that is obe...
Read more

Module 8: Isarithmic Mapping

Image
The purpose of this lab was to investigate the PRISM Interpolation Method to develop an isarithmic map of average annual precipitation for Washington state. PRISM is a model that calculates climate-elevation relationships from point data for each grid cell in a digital elevation model (DEM). The data set for Washington state includes annual precipitation over a 30 year period (1981-2010). In this lab, I explored two methods for symbolizing this data in ArcGIS Pro. The first symbolization method was using continuous tone symbology. Continuous tone symbology symbolizes a feature with differing shades between contours, where each point on the surface is shaded with a tone proportional to the value of the surface at that point. This results in a map where the shade of the colors vary and blend between contours, creating a smooth surface. A hillshade effect was applied to the map by using the Dynamic Range Adjustment (DRA) Hillshade Effect and editing the color and transparency of a co...
Read more