NRES 201
Lab 6
Introduction to ArcGIS and Spatial Analysis
The purpose of this computer laboratory is to give you a little experience in working with spatial
data. In particular, you will learn how to use ArcGIS to create a spatial plot of the observed data,
as well as summary statistics (e.g., the histogram). Finally, you will make a spatial map of your
using an interpolation method outlined subsequently.
Tasks for the week:
1) Review of basic PC use (create a working folder; use of EXCEL, database management).
2) Have a very BRIEF introduction into ArcGIS, which includes learning how to convert an ASCII
file or Excel file into a shape file, and how to explore the data with Geostatistical Analyst.
3) Perform a preliminary exploratory data analysis to compare the utility of grid based versus
random sampling for characterizing soil phosphorous levels.
Background
Spatial variability in soil physical and chemical properties poses a serious challenge for
agricultural production systems and natural resource management. Soil sampling is one of
the chief methods of characterizing these properties, yet costs are often prohibitive, which
results in relatively sparse spatial sampling. As a consequence, spatial maps of soil nutrient
levels and other soil properties of interest (soil type, pH, etc.) are often fraught with
uncertainty. Yet with the advent of numerous precision technologies such as yield
monitors, GPS, variable rate application equipment, remote sensing, etc., there is an
increasing emphasis in agriculture to use site-specific management (SSM) as a means of
improving the economic viability of production systems. For SSM to be successful, it is
essential to understand the uncertainty associated with various spatial sampling schemes.
There are currently several approaches for soil sampling. These are sampling by 1)
Management Zones, which are identified on the basis of soil type maps, yield records, and
remote sensing, 2) Grid-based Sampling, which usually consists of collecting samples on a
predefined grid system, with samples consisting of a composite of spatially distributed
samples, and finally, Random sampling, which is best suited to whole-field management
approaches.
Assignment:
Two datasets are provided on the NRES web page where you downloaded this lab writeup. The
first, WFRand.dbf, contains approximately 250 sample records from a quasi-random sampling of
the 640 ac Williams Field. The second, WF_2_5.dbf, also contains approximately 250 records, but
these are a grid-based sample design of roughly 2.5 acres/sample. Within the common S drive on
your computer in LIAC 029, you will find a folder with the name “temp”. Create a subfolder with
your name under this folder and download the two data files into this subfolder. The datasets are
already converted into dbf IV format, which is a format that can be used by ArcGIS. (Note that
NRES 201 Lab 6 Intro to GIS/Spatial Analysis
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