Huntington District

US Army Corps of Engineers BUILDING STRONG®

Land Cover Comparison Using GIS

Joe Trimboli, MS, CFM Community Planner Huntington District 17 August 2009

…...and lots of SQL

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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 Cell with HUC8 value code, and original class codes of 1992 and 2001 land cover

Each HUC8 watershed with total cell count and new class codes

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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/2009HanoverLandCoverPoster2009.pdf