u.s. department of the interior u.s. geological survey analysis of resolution and resampling on gis...
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U.S. Department of the InteriorU.S. Geological Survey
Analysis of Resolution and Resampling on GIS Data Values
E. Lynn UseryU.S. Geological SurveyUniversity of Georgia
Michael P. FinnU.S. Geological Survey
The People Who Did the Work
Michael P. Finn, Computer Specialist Douglas Scheidt, Student Programmer Gregory Jaromack, Student Programmer Thomas Beard, Cartographic Technician Sheila Ruhl, Cartographic Technician Morgan Bearden, Cartographic
Technician John D. Cox, Cartographic Technician
Outline
Introduction and Objectives Study Areas GIS Databases for Parameter
Extraction AGNPS Parameter Generation Resolution Effects Resampling Effects Conclusions
Objectives
Develop GIS databases as input to Agricultural Non-Point Source (AGNPS) Pollution Model
Create a tool for generating input, executing the model, and analyzing output
Determine effects of resolution and resampling
Introduction -- AGNPS
Operates on a cell basis and is a distributed parameter, event-based model
Requires 22 input parameters Elevation, land cover, and soils data
are the base for extraction of input parameters
Study Areas
Four Watersheds Little River, GA Piscola Creek, GA Sugar Creek, IN EL68D Wasteway, WA
Georgia Watersheds
Agricultural areas with some woodland, wetlands, and small urban areas
Indiana Watershed
Agricultural area with primarily corn and soybean crops
Washington Watershed
Agricultural watershed with a variety of row crops and small grains
Watershed Boundaries
NAWQA Boundary Defined by USGS WRD personnel from
contour maps GIS Weasel
Automatically computed from DEM data
Comparison of Watershed Areas (hectares)
Resolution (m)
NAWQA GIS Weasel
30 33423.8 34885.8
60 33702.5 35089.2
120 34076.2 35493.1
210 34631.7 35986.1
240 34859.5 36241.9
480 36426.2 37739.5
960 39444.5 40458.2
1920 45711.4 46418.9
GIS Databases for Parameter Extraction
National Elevation Dataset (30-m) National Land Characteristics Data (30 m)
Augmented with recent Landsat TM data Soils databases from USDA soil surveys
Scanned separates, rectified, vectorized, tagged
Resampled the 30-m data to 60, 120, 210, 240, 480, 960, and 1920 meters 210-m roughly matches 10 acre grid size
AGNPS Parameter Generation
AGNPS Data Generator Input parameter generation Details on generation of
parameters Extraction methods
AGNPS Data Generator
Created to provide interface between GIS software (Imagine) and AGNPS
Developed interface for Imagine 8.4, running on WinNT/2000
AGNPS Data Generator
Input Parameter Generation
22 parameters; varying degrees of computational development Simple, straightforward, complex
Creating AGNPS Input
Input Data File Creation Format generated parameters into
AGNPS input file Use a “stacked” image file to create
AGNPS data file (“.dat”) -- ASCII
Input Parameter Generation
Details on Generation of Parameters
Cell Number Receiving Cell Number
SCS Curve Number Uses both soil and land cover to resolve curve number
Details on Generation of Parameters
Slope Shape Factor
Details on Generation of Parameters
Slope Length A concern; max value should be 300 ft.
Parameters 10, 11, 12, 14, 15, 16, and 17 Uses Spatial Modeler to lookup
attributes from soils or land cover Parameters 13, 18, 19, 20, and 21
Hard coded on advice from experts
Details on Generation of Parameters
Type of Channel Uses TARDEM program Creates a Strahler steam order
Extraction Methods
Used object-oriented programming and macro languages C/ C++ and EML
Manipulated the raster GIS databases with Imagine
Extracted parameters for each resolution for both boundaries using AGNPS Data Generator
Creating AGNPS Output
AGNPS creates a nonpoint source (“.nps”) file
ASCII file like the input; tabular, numerical form
AGNPS
Output
AGNPS Output
Creating AGNPS Output Images
Output Image Creation Combined “.nps” file with Parameter 1
to create multidimensional images Users can graphically display AGNPS
output Process: create image with “x” layers,
fill layers with AGNPS output data, set projection and stats for image
Multi-layered (bands) images per model event
Creating AGNPS Output Images
Creating AGNPS Images
Results
Resolution effects Tested with two independent
collections Elevation at 3 m and 30 m resolution Land cover at 3 m and 30 m resolution Comparison of values
Elevation
Easting Northing 3-m LC 30-m LC 3-m Elev 30-m Elev
239589 3504260 Crop Mature Planted Pine 119 122 241209 3503180 Crop Crop 125 124 256449 3486470 Urban Crop 102 103 252039 3491360 Mature Deciduous Wetland 84 85 240369 3516350 Mixed Deciduous/Pine Mature Planted Pine 132 132 253959 3486830 Urban Crop 90 85 253539 3496400 Urban Crop 111 111 246369 3497360 Mixed Deciduous/Pine Wetland 95 94 247779 3512330 Urban Urban 130 130 256179 3491270 Crop Crop 97 97 244239 3498170 Mixed Deciduous/Pine Mature Planted Pine 106 106 238449 3515090 Young Planted Pine Mature Planted Pine 132 130 254589 3486920 Mature Planted Pine Crop 84 85 244749 3504560 Crop Crop 121 119 250929 3495140 Crop Crop 107 100 247719 3498890 Crop Crop 115 112 244359 3507260 Crop Disturbed or Harvested land 116 115 255579 3491240 Mixed Deciduous/Pine Wetland 95 94 252339 3500660 Crop Crop 113 115 247719 3508160 Crop Crop 117 116
Sampling of Points for Land Cover and Elevation Comparisons for Little River, GA
Regression Results
3 m to 30 m comparison Elevations -- R2 of 0.81 Land cover – McFadden’s pseudo R2
of 0.139, meaning little correlation Derived parameters, e.g., slope,
problematic because of degraded data source
Results
Resampling effects
Experimental Approach
Analysis requires DEM, slope, and land cover at 30, 60, 120, 210, 240, 480, 960, 1920 m cells
Starting point is 30 m DEM and land cover Calculate slope at 30 m cell size from DEM Resample land cover How to generate slope at 60 m and larger
cell sizes? How to aggregate land cover?
Comparison of Number of Cells in Watersheds at Various Resolutions
Number of Cells Resolution (meters)
Little River
Piscola Creek
Sugar Creek
EL68D Wasteway
3 37076000 n/a 26659000 n/a 30 372390 494710 264400 419120 60 93618 124220 66560 104780
120 23664 31352 16670 26199 210 7853 10411 5450 8554 240 6052 8012 4159 6544 480 1581 2090 1040 1635 960 428 563 264 408
1920 124 159 65 102
Method of Calculation
Slope calculated from DEM 30, 60, 120, 210, 240, 480, 960, 1920 m
cells Compute slope from 30 DEM Aggregate DEM from 30 m to each
lower resolution Compute slope from aggregated
elevation data
30 m DEM 120 m DEM 120 m slope
60 m slope
30 m DEM 30 m slope 60 m slope
30 m DEM 60 m DEM
30 m DEM 30 m slope 120 m slope
Sample of Slope Generation Approaches
compute aggregate
aggregate
aggregate
aggregate
compute
compute
compute
Results - DEM
Regression Output:0.980539Constant3.105509Std Err of Y Est0.959085R Squared
34No. of Observations32Degrees of Freedom
0.983164X Coefficient(s)0.035898Std Err of Coef.
120-210m30-210m76766153464978767578464569707167575660636465606038385152
Results - DEM
Regression Output:-1.38617Constant2.274152Std Err of Y Est0.97968R Squared
10No. of Observations8Degrees of Freedom
1.010755X Coefficient(s)0.051466Std Err of Coef.
210-480m30-480m65636365404061614849787756623334616132335356
Image Results -- DEM
30-480 m Pixels 210-480 m Pixels
Results -- Slope
Slope %30 to 480m
Pixels
7.8816 7.8232 7.5870 7.8251 8.1604 8.5415 8.2065 7.9530 7.7434 7.7092
Slope %210 to 480m
Pixels
7.9514 7.8969 7.6244 7.7855 8.1263 8.5087 8.2157 7.8606 7.6390 7.6081
Regression Output:
Constant 0.2762 Std Err of Y Est 1.1626 R Squared 0.7690 No. of Observations 500 Degrees of Freedom 498
X Coefficient(s) 0.8860
Std Err of Coef. 0.0218
Results -- Slope
Slope Method of calculation affects results Higher resolution aggregation
directly to large pixel sizes yields better results than multistage aggregation (e.g., 30 m to 960 m is better than 30 m to 60 m to 120 m to 240 m to 480 m to 960 m)
Even multiples of pixels hold results while odd pixel sizes introduce error
Slope Image Comparison30 m to 480 m pixels 210 m to 480 m pixels
Sample of Land Cover Aggregation Approaches
30 m LC 210 m LC 480 m LC
210m LC
30 m LC 60 m LC 120 m LC
30 m LC 120 m LC
30 m LC 960 m LC 1920 m LC
aggregate aggregate
aggregate aggregate
aggregate aggregate
aggregate aggregate
Results - Land Cover -- 120 M Pixels
30_original
2360.07
14026.41
8667.72
8607.87
17203.86
4669.65
14773.41
25133.67
5554.08
583.83
22166.55
120_30res
2466.72
14224.32
8786.88
8627.04
17343.36
4743.36
14860.8
25509.6
5705.28
593.28
22432.32
30-120 %
-4.52
-1.41
-1.37
-0.22
-0.81
-1.58
-0.59
-1.50
-2.72
-1.62
-1.20
Land Cover Category
Pecan Groves
Recently Disturbed Land / Harvested Cropland
Pastures
Cypress Dominant Weltands
Mature Deciduous
Young Planted Pine
Mature Planted Pine
Mixed Dominant Deciduous / Pine
Roads / Urban Complex
Open Water
Crops (Cotton, Peanuts)
Results - Land Cover -- 210 m Pixels
210_30res
2424.048
14632.4352
8492.98272
8625.20352
17536.88544
4689.43104
15527.12928
25465.72608
5641.4208
612.62304
22213.0944
210_120res
2500.71948
14413.31792
8679.74592
8812.05912
17169.84292
4600.08892
14894.05588
25624.6564
5680.64672
648.33468
22171.28188
210 % diff
-3.16
1.50
-2.20
-2.17
2.09
1.91
4.08
-0.62
-0.70
-5.83
0.19
Land Cover Category
Pecan Groves
Recently Disturbed Land / Harvested Cropland
Pastures
Cypress Dominant Weltands
Mature Deciduous
Young Planted Pine
Mature Planted Pine
Mixed Dominant Deciduous / Pine
Roads / Urban Complex
Open Water
Crops (Cotton, Peanuts)
Results - Land Cover -- 480 m Pixels
210-240d30-240d30-210d480_240res480_210res480_30res
-36.45-10.4419.062764.80002026.30562503.3376
8.773.29-6.0013570.560014874.925214032.4704
-5.332.507.438755.20008312.45828979.8624
6.511.98-4.858847.36009463.76829025.7952
-7.010.346.8717372.160016233.471017431.4976
-8.06-11.70-3.364976.64004605.24004455.4816
3.11-4.35-7.7015505.920016003.209014859.2608
0.65-0.23-0.8925735.680025904.475025676.4352
6.98-8.04-16.145483.52005894.70725075.5744
-30.51-20.387.76691.2000529.6026574.1600
-0.992.973.9222440.960022220.283023127.1648
Land Cover Category
Pecan Groves
Recently Disturbed Land / Harvested Cropland
Pastures
Cypress Dominant Weltands
Mature Deciduous
Young Planted Pine
Mature Planted Pine
Mixed Dominant Deciduous / Pine
Roads / Urban Complex
Open Water
Crops (Cotton, Peanuts)
Results-Land Cover -- 960 m Pixels
Land Cover Category
Pecan Groves
Recently Disturbed Land / Harvested Cropland
Pastures
Cypress Dominant Weltands
Mature Deciduous
Young Planted Pine
Mature Planted Pine
Mixed Dominant Deciduous / Pine
Roads / Urban Complex
Open Water
Crops (Cotton, Peanuts)
210-480d30-480d30-210d960_480res960-210res960_30res
-19.69-3.1213.842755.974 2302.61752672.64
11.542.93-9.7413688.0042 15473.589614100.48
-18.79-12.415.389737.7748 8197.31838663.04
0.26-12.68-12.989554.0432 9578.88888478.72
-9.94-0.208.8617821.9652 16210.427217786.88
17.7611.60-7.484317.6926 5249.96794884.48
9.015.76-3.5714331.0648 15749.903715206.4
0.942.651.7326916.6794 27170.886527648
21.4223.773.004777.0216 6078.91026266.88
40.1640.190.06275.597460.5235460.8
-8.52-6.741.6324987.523026.17523408.64
Image Results - Land Cover
30-480 m Pixels 240-480 m Pixels
Image Results - Land Cover
30-210 m Pixels 120-210 m Pixels
Statistical Testing
Selected 500 random points over the watershed
Compared elevation, slope, and land cover values at the 500 points
Computed R2 and pseudo R2 between resolutions
Plotted R2 and pseudo R2 against resampled resolutions from 30 m data
Resample Coeffient of DeterminationElevation -- Little River Watershed
60120
480
1920
960
210240
0.000.100.200.300.400.500.600.700.800.901.00
0 500 1000 1500 2000
Resampled Size(From 30 meters)
R2
Resample Coeffient of DeterminationLand Slope -- Little River Watershed
60
1920
480
120
240
210
9600.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0 500 1000 1500 2000
Resampled Size(From 30 meters)
R2
Resample Coeffient of DeterminationFlow Direction -- Little River Watershed
Multinominal Regression
60
1920480
120
240210
9600.00
0.10
0.20
0 500 1000 1500 2000
Resampled Size(From 30 meters)
Pseudo R2
Comparison of Land Cover Values across Resamplings for Little River (Values are percentages of 30-m land cover category areas).
60-m 120-m 210-m 240-m 480-m 960-m 1920-m Water 100.12 94.50 121.23 97.04 98.56 65.71 0.00
Urban 104.04 94.34 100.28 76.73 68.51 35.97 89.98
Transitional 100.54 96.96 92.18 90.15 81.95 69.34 90.20
Deciduous 103.35 101.65 102.12 94.36 120.21 156.28 97.74
Pine 100.11 98.48 97.90 96.80 86.37 69.99 48.35
Mixed 98.18 101.29 94.74 98.41 86.33 65.95 148.47
Crop 98.99 97.72 95.42 95.80 91.40 88.33 74.46
Wetlands 99.50 100.27 99.98 102.78 101.91 105.47 82.45
Conclusions
Automatic generation of AGNPS parameters from elevation, land cover, and soils
Resolution affects results Elevation and derivatives (slope) hold
values well because of averaging methods of resampling
Land cover (categorical data) is inconsistent across resolutions because of nearest neighbor resampling
Conclusions
Resampling retains values better with even multiples of original pixel sizes
Aggregation directly from higher resolution to lower retains values better than multiple intermediate resampling
U.S. Department of the InteriorU.S. Geological Survey
Resolution and Resampling Effects of GIS Databases for Watershed Models
E. Lynn UseryU.S. Geological SurveyUniversity of Georgia
Michael P. FinnU.S. Geological Survey
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