Presentation given at 2009 Ohio Floodplain Managers Conference and Poster displayed at Hanover College Rivers Institute Conference

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Land Cover Comparison Using GIS
…...and lots of SQL
Joe Trimboli, MS, CFM
Community Planner
Huntington District
17 August 2009
US Army Corps of Engineers
BUILDING STRONG®

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Land Cover Comparison
Need for Comparison
 Ohio River Basin Comprehensive Report Study
(ORBCRS)
 www.orboutreach.com

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Land Cover Comparison Goals
Identifies land use changes in the Ohio River
Basin
Incorporate map set into MapRecon portion of
study
 Create access table that links to HUC8 watershed for
map creation
 Create map for each land cover classification

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Data
Sources
 National Land Cover Datasets of 1992 and 2001
 Downloaded from USGS
 Used seamless server
 Template Selection
 Best meta data available
 USGS Watershed Layer (CORPSMAP)
 CorpsMap is the USACE nationwide enterprise GIS
implementation
 Data source for many federal agencies

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Data Preparation
 Created mosaic raster layer using ArcMap 9.2 for
each data set, 1992 and 2001 (6 template areas)
 Created raster of HUC8 watersheds
 Insured all raster’s had same projection
 Matched land cover projection
 Converted HUC8 data to match land cover data
 Insured all raster's had same cell size
 Defined HUC8 raster layer to match land cover cell size

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HUC8 raster
file
reprojected
and with
matching
cell size to
land cover
layers

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Process Verification
 Used various processes
 Evaluated data numerous times
 Different tools Different ways
 Model Creation
 Spatial Analyst Tools > Combine

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Model
creation
proved to
be awkward
and time
consuming
based on
existing
knowledge

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Found
Combine
tool while
researching
process

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Combine
 Creates new raster layer
 Combines multiple layers
 Intersecting raster cell values
 Creates Discrete properties table NOT Floating Point

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Adds
columns' in
attribute
table that
correspond
to each
raster layer

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Data Check:
Identify point
on map
Open
Attributes
Table
Scroll to
matching
pixel value
Verify layers
and column
names

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Export all
attribute
tables to
Microsoft
Access

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Microsoft Access (SQL)
 Format of Personnel Geospatial Database
 Manipulates tables
 Ability to create and manipulate data
 Non-spatial Tables
 Creation custom queries

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Tables

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Land Cover Comparison Goals
Identifies land use changes in the Ohio River
Basin
Incorporate map set into MapRecon portion of
study
 Create access table that links to HUC8 watershed for
map creation
 Create map for each land cover classification

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Comparable Study

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USGS Data Research

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NLCD 1992-2001 Anderson Level I Cross-walk Table

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Crosswalk Table Creation

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Original Class Values from Raster Layer

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Cross walk tables
Create tables from original raster layer table and
corresponding USGS modified Anderson Level I
table information. Created new Description.

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Unique Anderson Class Table

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Unique Anderson Class Table - Update

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Unique Anderson Class Table - Update

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Class Table Importance
There must be the same number of classes in
each comparison year for a DIRECT comparison
 Not an issue at the larger Ohio River Basin level
 Not an issue at smaller area comparisons
 Issue at the HUC8 scale of comparison

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Make Table Query

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HUCAnderson with Combine1
Each HUC8 watershed with total Each Cell with HUC8 value code, and
cell count and new class original class codes of 1992 and 2001
codes land cover

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Reclass Query Design
All like values are linked between
tables

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Reclass Query Results 1992

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Reclass Query Results 2001

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Time to Merge Tables

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Initial Merge Results

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Initial Merge Results
How do you
calculate
change
percentage and
map it?

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SQL Formulas

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SQL Formulas
1992 & 2001
IIf(IsNull([1992reclass!COUNT]),0,[1992reclass!COUNT])
ChangeRatio:
IIf([1992]=0,([2001]/HUCAnderson!Total),[2001]/[1992])
Percentage:
IIf([2001]>[1992],[changeratio]*100,[changeratio]*-100)

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Results

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Almost There…

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Single Class Queries

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Single Class Queries

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Final Goal

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Final Goal

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Accuracy Concerns – 1992 Original

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Accuracy Concerns - 2001

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Accuracy Concerns – 1992 modified

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Resulting Hypothesis
The land cover change from different sources is
outside the 9% standard distribution curve of the
percent change (location quotients) of the
watersheds. The 90% represents the difference
of equipment and seasonal variation.

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Land Cover Comparison
1992 and 2001 land cover data was downloaded
from the USGS National Map Seamless Server
and reclassified based on the USGS Anderson
Level I cross walk table. Both layers were then
combined using ESRI ArcView and the
supporting tables exported to Microsoft Access.
The tables were then manipulated to extract the
location quotients (LQ) for each class and joined
based on HUC8 values. A HUC8 class table was
created that insured a direct comparison of 7
classes.

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Poster
A poster was from ESRI ArcMap with charts
created in Microsoft Excel. Two large panels
represent the Anderson Level I classified land
cover for the project area. Small 7 map panels,
one for each land classification,were mapped
based on the standard deviation (StdDev) of the
location quotients calculated in Microsoft
Access. The StdDev values of the LQ’s within
the 95% range were then mapped hollow. The
charts reflect the raw LQ values crossing at the
value of one.

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Questions
?

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Internet Atlas
Ohio River Comprehensive Reconnaissance
Study (ORBCRS)
 http://www.tinyurl.com/orbmaps
 http://www.lrh.usace.army.mil/silver_jackets/ORB/thu
mb.html
 http://www.lrh.usace.army.mil/silver_jackets/ORB/200
9HanoverLandCoverPoster2009.pdf