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Tuesday, September 24, 2024
Monday, September 16, 2024
GIS 5935 Module 2.1 - Surfaces [Triangulated Irregular Networks and Digital Elevation Models]
Module 2.1 of Special Topics in GIS was based on surfaces, particularly Triangulated Irregular Networks [TINs] and Digital Elevation Models [DEMs]. The first portion of the lab was an opportunity to import elevation data, set the ground source [giving it 3D visualization], and learning how to exaggerate the vertical distances to enhance the visual aesthetics of the landscape. Once these fundamental concepts were practiced, an analytical problem was presented.
The second portion of the lab was to create a Suitability Map for a study area that illustrates the best locations for a ski resort and its associated ski run. The suitability was determined based on slope, elevation, and aspect [directional face] of the landscape. The dark green areas of the map below display the most suitable locations of the resort, and the red areas signify areas that are unsuitable for this tourist destination.
Tuesday, September 10, 2024
GIS 5935 Module 1.3 - Data Quality Assessment
Module 1.3 of Special Topics in GIS was a continuation of data quality; this module focused on the completeness of datasets, roadway networks particularly. Two datasets were provided for the completeness assessment; one was obtained from Jackson County, Oregon and the other was downloaded from the United States Census Bureau TIGER shapefile repository. While both datasets contained roadway centerlines, their overall distances were significantly different. The spatial analysis performed on these datasets was to ascertain which one was more complete, based on length alone. Initially, before any processing was performed, the TIGER shapefile consisted of 11,382.7 kilometers of roadway centerlines while the Jackson County dataset accounted for 10,873.3 kilometers, making the TIGER dataset more complete.
The next process of this lab was to analyze completeness according to [Haklay, 2010]. Essentially, this method consists of overlaying a grid index on top of the datasets and creating a thematic map according to their percentage differences. For this lab, the grid consisted of 5-kilometer squares that were set within the confines of the county border. Next, all roadways that lied outside of the grid index were clipped; this deleted any extra roadways outside the confines of the grid. After this, the roadways had to be split at the intersection of each grid cell, and then the individual roadway sections within each cell had to be dissolved into one multi-part feature. Once these processes were completed for each dataset, a comparison between the two could be made on a cell-by-cell basis [see map below].
[[Jackson County Length - TIGER Length] / Jackson County Length] * 100
Haklay, M. (2010). How Good is Volunteered Geographic Information? A Comparative Study of OpenStreetMap and Ordinance Survey Datasets. Environmental and Planning B: Planning and Design, 37(4). 682-703.
Monday, September 2, 2024
GIS 5935 Module 1.2 - Spatial Data Quality
Lab assignment 1.2 of Special Topics in GIS was performing an accuracy assessment according to the National Standard for Spatial Data Accuracy. Positional Accuracy Handbook states 'the National Standard for Spatial Data Accuracy describes a way to measure and report positional accuracy of features found within a geographic dataset. Approved in 1998, the NSSDA recognizes the growing need for digital spatial data and provides a common language for reporting accuracy' [Planning, 1999]. For this assignment, two datasets were provided for a study area located in the City of Albuquerque, New Mexico. The first dataset was obtained from the City of Albuquerque and the second was a StreetMap USA dataset, which is a product of TeleAtlas and is distributed by ESRI with the ArcGIS software package. Both datasets consist of roadway networks and can be seen in the map below. The green lines represent the City of Albuquerque [ABQ] dataset, and the red lines represent the StreetMap USA dataset.
ABQ Dataset:
Using the National Standard for Spatial Data Accuracy, the data set tested 14.27ft horizontal accuracy at 95% confidence level.
StreetMap Dataset:
Using the National Standard for Spatial Data Accuracy,
the data set tested 379.66ft horizontal accuracy at 95% confidence level.
Example of Detailed positional accuracy
statements as reported in metadata:
Digitized features of the roadway infrastructure located
within the study area of Albuquerque, New Mexico were obtained from the City of
Albuquerque and from StreetMap USA, a product of TeleAtlas and distributed by
ESRI with ArcGIS. Those obtained from the City of Albuquerque tested at 14.27ft
horizontal accuracy at the 95% confidence level, and those obtained from
StreetMap USA tested at 379.66ft horizontal accuracy at the 95% confidence
level using modified NSSDA testing procedures. See Section 5 for entity
information of digitized feature groups. See also Lineage portion of Section 2 for
additional background. For a complete report of the testing procedures used,
contact the University of West Florida GIS Department as noted in Section 6,
Distribution Information.
Levels of vertical relief were not considered throughout
the entire accuracy assessment of these two datasets.
Source:
Planning, M. (1999). Positional Accuracy Handbook. Using the National Standard for Spatial data Accuracy to measure and report geographic data quality. Minnesota Planning, St. Paul, MN.
GIS 5935 Module 2.2 - Surface Interpolation
Post in progress - please check back soon...
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Lab assignment 1.2 of Special Topics in GIS was performing an accuracy assessment according to the National Standard for Spatial Data Accura...
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For the Final Project of this course, we performed a Geospatial analysis of the proposed location of the Bobwhite-Manatee Transmission Li...
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My research project for Remote Sensing and Photo Interpretation was modeled after a case study named " Mapping the Dynamics of Eastern ...