Part II: Section A
Using GIS Technology
2.1 Base Maps - Part 1

Base maps are geographic data that form the foundation upon which all other map data are overlain. They consist of a multi-layered compilation of geographic data about each field, including features such as soil types and topographic contours. As the growing season progresses, subsequent data are overlaid on these base maps. In addition, base maps allow for the measurement of each field’s surface area, facilitate the placement of goose exclosures and their paired-grazed plots, quantify each field’s spatial characteristics and position, and use spatial analysis techniques to assess impacts on yield.

Once a farmer has made the decision to assess the impact of goose grazing in a particular field, the farmer must:

  Gather all information pertinent to the selected field:
    -   Previous yield maps
    -   Aerial photography
    -   Grazing patterns (indicate where heavy grazing may occur)
  Contact the provider to schedule a field visit
For the field visit the provider will take:
  Differential GPS unit to:
    -   Delineate the field boundary
    -   Locate exclosures
  Laptop computer loaded with GIS software and data, as detailed in the next paragraph
GIS Software

A geographic information system is an assemblage of computer hardware and software tools designed for capturing, storing, checking, integrating, manipulating, analyzing, and displaying data that are spatially referenced to the Earth. There are several commercial GIS packages available to users for performing the necessary steps to quantify goose impact on yield. This manual is not intended to replace the user’s guide for specific software. The user is best served by choosing the program he or she is most comfortable operating. Different software will perform the same tasks, such as overlying and clipping, with the end result being the same. Numerous GIS software packages have developed digital data structures and basic GIS data standards that now allow quick and easy incorporation of many types of digital layers into a GIS database. For the purpose of this manual, we will be using Arc/View ® 3.X GIS software. ArcView ® is one of the numerous GIS packages available and was developed by Environmental Systems Research Institute, Inc. (ESRI), a commercial company with headquarters in Redlands, California (

- Data Readily Available:

The data needs to be detailed, accurate and most importantly, georeferenced (referenced to a specific location in the farm field). Georeferenced data representing several themes could be overlaid in a GIS environment. Each attribute collected during field observations represents a separate layer. The Meta data file should provide all information regarding each data. We recommend using the Universal Transverse Mercator coordinate systems and the 1983 North American Datum. The western part of Oregon is located within the zone 10 North.

Zone 10 North

Soil Map

Digital soil types are available on the Internet and from commercial sources. The United States Department of Agriculture Natural Resource Conservation Service (NRCS) provides digital soil maps. Field mapping methods using national standards are used to construct the soil maps in the Soil Survey Geographic (SSURGO) database. The mapping scales in Oregon generally are 1:24,000. This is the most detailed level of soil mapping done by NRCS.

How to obtain soil maps?

The files are in ArcExport format and zipped using WinZip 7.0. The user must unzip and import the files before viewing them with GIS software.

Multnomah County shown below as an example (Figure IIA_3). To download digital soil survey data for Oregon click on the following link:


Figure IIA-3: Sample of soil map: Multnomah County, Oregon.


USGS Digital Orthophotographic Quarter Quadrangles (DOQs)

A Digital Orthophoto (Quarter) Quadrangle, also known as DOQ, is a rectified digital image of an aerial photograph, with distortion and displacements removed and corrected for aircraft pitch, yaw, and altitude; camera tilt; and terrain relief, thus conforming to the properties of an orthographic projection. The finished product is a spatially accurate image with ground features represented in their true planimetric positions. A DOQ is, therefore, a computer-generated image of an aerial photograph that combines the image characteristics of a photograph with the geometric qualities of a map. The digital image is a GIS product that can be overlaid and manipulated like any other coverage or layer and offers significant flexibility.

The aerial photographs are digitized and processed to produce 3.75 x 3.75-minute DOQs with 1-meter ground resolution and mapped to 1:12,000 scale accuracy specifications. The image transformations are cast on the Universal Transverse Mercator (UTM) projections based on the North American Datum of 1983 (NAD 83). Also, each DOQ image has between 50 to 300 meters of overlap to facilitate tonal matching for mosaicing of adjacent maps or images. A grayscale DOQ requires about 46 MB of storage space per 3.75-minute or quarter-quadrangle region (EROS/USGS web site).

How to obtain DOQQ?

Orthophotographs of agricultural land (Figure IIA-4) are available from some commercial or government sources. State or county-level coverages can be downloaded from:

The GIS Data Depot site:

The Oregon Geospatial Data Clearinghouse:

Click on Alphabetical listing.

The Earth Resources Observation Systems (EROS) Data Center (EDC):

Figure IIA-4: Samples of DOQ maps. DOQQ maps used to show ponded areas (above) and to provide background to delineate field boundaries (below).


USGS Digital Raster Graphics (DRG)

A digital raster graphic (DRG) is a scanned image of a U.S. Geological Survey (USGS) standard series topographic map, including all map collar information (Figure IIA-5). The image inside the map neatline is georeferenced to the surface of the Earth and fit to the Universal Transverse Mercator projection. The horizontal positional accuracy and datum of the DRG matches the accuracy and datum of the source map. The map is scanned at a minimum resolution of 250 dots per inch and saves in TIFF format (EROS/USGS web site).

How to obtain DRGs?

From the USGS
The USGS distributes DRGs on Compact Disc-Recordables (CD-R). DRG orders are filled on demand. The sale of DRGs in fixed 1-degree blocks was discontinued on October 1, 1998, and the current policy allows the ordering of any combination of quadrangles. DRGs may also be ordered online from USGS Earth Explorer.

From the Internet
A complete set of 1:24,000 scale Digital Raster Graphics files in Zip format covering the states of Oregon and Washington can be found at:

The Regional Ecosystem Office (REO):

Or the Earth Resources Observation Systems (EROS) Data Center (EDC):

Figure IIA-5: Samples of DRG showing Sauvie Island, Oregon.


Digital Line Graphs (DLGs)

A DLG is line map information in digital form. DLG data files include information about planimetric base categories such as transportation, hydrography, and boundaries (EROS/USGS web site). Other vector information such as roads, streams, and field boundaries can be overlaid onto DOQQ raster maps (Figure IIA-6). This allows for the mapping of relative position of other features visible on the orthophotos, such as trees, thickets, and dwellings, and to determine linear distances from visible objects to all points in the field.

How to obtain DLG?

Oregon Geospatial Data Clearinghouse:

The Earth Resources Observation Systems (EROS) Data Center (EDC):

Figure IIA-6: Sample of DLG for the southern part of Sauvie Island.


USGS Digital Elevation Models

The Digital Elevation Model data files are digital representations of cartographic information in raster form (Figure IIA-7). DEMs consist of a sampled array of elevations for a number of ground positions at regularly spaced intervals. These digital cartographic/geographic data files are produced by the U.S. Geological Survey as part of the National Mapping Program and are sold in 7.5-minute, 15-minute, 2-arc-second (also known as 30-minute), and 1-degree units. The 7.5- and 15-minute DEMs are included in the large-scale category, while 2-arc-second DEMs fall within the intermediate-scale category and 1-degree DEMs fall within the small-scale category (EROS/USGE web site).

How to obtain DEM?

You can download 10-meter DEM for the State of Oregon from the Regional Ecosystem Office (REO):

The Earth Resources Observation Systems (EROS) Data Center (EDC):

Figure IIA-7: Sample of a 10m DEM for the Northeastern, Oregon.


- Generated Data Layers
Generating Random Points for Exclosures Placement

Random Placement of Paired Plots

It is desirable to have paired plots distributed throughout the field. Furthermore, efforts should be undertaken to ensure that paired plots for each soil type are included in the sampling design. In these situations, stratified random sampling will be the most efficient and meaningful method for selecting samples. When using this method, the field (population) to be sampled is first divided into meaningful sub-units or strata based on grazing location and soil characteristics.

The selection of random locations within each strata should be independent of other units that have been sampled. A relatively simple and reliable method for randomization is to use random numbers. Most spreadsheet, database, statistical programs, GIS software have functions that generate random numbers. The randomization process conducted here is performed using Arc/View ® GIS software along with two Arc/View ® extensions (GIS program/script):


AlaskaPak is an extension for use with ArcView 3.x. It provides a suite of general utilities for use in a variety of GIS projects. Designed and programmed by the GIS Team of the National Park Service’s Alaska Support Office, the utilities are particularly useful for natural resource and cultural resource needs. The extension is free to download, and all code is available within the extension for public use or modification. This extension can be downloaded from the following site:

Animal Movement Analysis
The Movement extension is a collection of more than 40 functions to aid in the analysis of animal movement data.  One useful operation is the creation of random point theme. This is done with a selected record of a polygon theme or polygon graphic as the boundary.  The user selects the polygon record or graphic, then specifies number of points, distance from boundary, and distance from other points.  You can download this extension from:


Factors to Consider

Exclosure distribution should represent all parts of the field. There are several key factors to keep in mind when considering exclosure placement.

Field size and shape: Exclosures may influence which fields or parts of fields are grazed. Narrow, long fields have more perimeter than open, large fields (Figure IIA-8). This has to do with edge effect. Geese tend to avoid grazing too close to the boundary.

Figure IIA-8: Field shape. Narrow long field (left) and open large field (right).

Number of exclosures: Too many exclosures in one area may cause geese to shift to other parts of the field or avoid the field entirely.

Size of exclosures: For harvesting at a rate of approximately 2 mph, the recommended exclosure size is 20 by 65 feet. If harvest rate increases, length of exclosure should increase accordingly. You should obtain 15 samples per exclosure. Each 1 mph = ~ 1.5ft/sec. At a 3 mph harvest rate, the 65-feet exclosure length should yield about 15 data points. At 5 mph, the exclosure would have to be 115 feet long to produce 15 data points. In that case, it would be more efficient to increase the exclosure length to 130 feet and use two 150-foot rolls of poultry wire (130 feet long by 20 feet wide).

. Note: we have not evaluated the influence of longer exclosures on goose behavior.

Soil Type: Include at least two exclosures for every main soil type. Small patches of differing soils are not pertinent to the analysis and should not be considered for exclosure placement (Figure IIA-9).

Figure IIA-9: For this field, disregard the small inclusions of Moag silty clay loam and Rafton silty loam


Goose grazing intensity: Concentrate more exclosures in strata of the field that, based on past observation, are expected to be heavily grazed. Stratify a field into two or three units based on anticipated grazing intensity (e.g., more intensive, less intensive, and no grazing).

Combine Turnings: Avoid placing paired plots where swathers and combines turn (Figure IIA-10).

Figure IIA-10: Previous yield-map.

Water damage: avoid placing paired plots in ponded areas (Figure IIA-11).

Figure IIA-11: A DOQ showing areas impacted by water.


Steps for Generating Random Point Locations

First delineate area of goose use/soil type/intensity of grazing. From this point on, we will use ArcView®. Before starting it is important to understand some terms that are used frequently during an ArcView® session.

<< previous page  
1. Introduction
2. Data Collection
- 2.1 Base Maps
--- Part 1
--- Part 2
- 2.2 Yield Factor Maps
- 2.3 Yield Map

3. Data Analysis
4. Findings/Summary
All information, data, design, and graphics are copyright (c) 2003 Dept of Rangeland Resources, Oregon State University. All rights reserved.