NR402 GIS Applications in Natural Resources€¦ · NR402 - GIS Applications in Natural Resources The flat top of Craig Mountain is forested Photo: S. Bunting Many of the datasets

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NR402GIS Applications in Natural Resources

Lesson 2 - Vector Data

Points Polygons Lines

Coordinate-based data structures commonly used to represent map objects. Each object is represented as a list of X,Y coordinatesExamples - tree, poles, roads, housing developments, zoning districts

This lesson will focus on analysis tools for vector data. Be aware that there are two completely different suites of tools in ArcGIS; one that works for vector data and one that works for raster data. You cannot use the vector data tools on raster data and vise versa. It is therefore very important to always be aware of what data type you are working with.In Lesson 1 you learned that there are three representations of real world objects when working with vector data in GIS: points, lines and polygons. Raster data is composed of cells (pixels, squares) of a certain size.

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NR402 - GIS Applications in Natural Resources

GIS AnalysisGIS Analysis

• Overlay Analysis• Proximity Analysis• Distance analysis

• Working with tables• export table to Excel• work with tables in ArcMap

GIS is a tool where you can explore two or more data layers together to reveal relationships that were previously unknown. In Lab 2 you will use the ArcToolboxanalysis tools to perform an overlay analysis and a proximity analysis on vector data. Vector data analysis commonly result in tabular data. These tables can be further analyzed in the GIS software or exported to other database programs such as Microsoft Excel or Access.

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Analysis Tools in Arc ToolboxAnalysis Tools in Arc Toolbox

Extract (clip)

Overlay (Intersect, union)

Proximity (buffer)

Extract (clip)

Overlay (Intersect, union)

Proximity (buffer)

ArcToolbox is launched directly from ArcMap – the icon looks like a red toolbox. In exercise 2 you will be using tools located under the ‘Analysis Tools’ tab in ArcToolbox. In Exercise 2 you will be using the clip, intersect, and buffer tools.

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Overlay analysis point dataOverlay analysis point data

“Piercing Needle” Approach

• Multiple layers of data are in relative position with one another - inserting a "digital pin" through the stack of overlayed data.

• This allows questions to be answered concerning everything occurring at a particular location.

• This view of the world limits focus to a particular point and precludes wide-area landscape analysis.

Two overlay analysis principles will be described here: 1 – the piercing needle approach 2 – the cookie cutter approach. Both methods involves extracting data from multiple GIS data layers at locations of interest. In the ‘piercing needle approach’ information from one or more data layers are extracted at one single point (point – polygon overlay). For example, you may want to know the habitat type and canopy cover at bird nest locations. In this case the bird nests are represented by a point layer and the habitat type, elevation and canopy cover is represented by individual polygon data layers. The result of such an analysis will be a table that contains the habitat type and canopy cover for each bird nest location in your dataset.

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Overlay Analysis for RegionsOverlay Analysis for Regions

Vector data• Clip• Intersect – Union

Raster data• GRID clip (masking)• Zonal statistics (GRID)• Combine

Region Wide: "Cookie Cutter Approach"

The other overlay approach is the ‘cookie cutter approach’ . This is an example of a polygon to polygon overlay analysis. Going back to the bird nest example, rather than extracting data from the exact bird nest location it might be interesting to analyze the conditions within a 100 meter buffer around the bird nest.The first step in such an analysis would be to create a 100 m buffer around the points (nests). The buffers will be represented in a new polygon layer in GIS. Next you would clip or intersect the habitat and canopy cover layers with the buffer layer and finally summarize the habitat types and canopy cover classes within the buffers.If your habitat and canopy cover layers are represented by raster data you would use the raster tools masking, zonal statistics or combine rather than the vector tools clipand intersect.

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Questions answered with GIS overlay analysisQuestions answered with GIS overlay analysis

• How much ponderosa pine forest is there on Moscow Mountain?

• How much mature timber burned in the Roberts fire?

• How many harvesting units on the UI Experimental Forest grow on slopes steeper than 30%

• What is the typical vegetation within 200 m of Lewis’s woodpecker nests?

• What is the area of aspen woodlands in the game management area?

Do you have a question that could be answered using GIS overlay or proximity analysis?

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Overlay Analysis - pointsOverlay Analysis - points

Spatial Analyst: Convert the point file to a raster based on a unique point ID.Perform the overlay analysis in the Spatial Analyst Raster Calculator by typing at the command line:Overlaygrid = combine(pointgrid, valuegrid)where overlaygrid is the name of the output grid

pointgrid is your converted point gridvaluegrid is the grid you want to extract information from

Point to Grid

Join and Relates: Join – Join data based on spatial locationHint: Right-click on the point layer, select Joins and Relates

Point to Polygon

Tool to use in ArcGIS 9xOverlay type

Different overlay analysis tools are used in ArcGIS depending on what type of overlay analysis you want to do. Different tools are used for vector and raster data and the tool used also depends on the vector data type, point, line or polygon.The instructions on this slide helps you find the correct tool for the overlay analysis you want to do.

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Overlay Analysis - areaOverlay Analysis - area

Tools to use in ArcGIS 9xOverlay type

Spatial Analyst: Raster CalculatorOutgrid = Combine(grid1, grid2)

orArcToolbox – Spatial Analysis Tools

Grid to Grid

Convert the polygon cover to a grid or the grid to a polygon and use the ‘poly to poly’ or ‘grid to grid’techniques

Spatial Analyst – Zonal Statistics (can handle overlay between polygon layers and grids)

Poly to Grid

ArcToolbox- Analysis Tools - Overlay – Clip, Intersect or Union

Poly to Poly

Different overlay analysis tools are used in ArcGIS depending on what type of overlay analysis you want to do. The Analysis Tools in ArcToolbox are useful for overlay analysis between two polygon data layers while the Spatial Analysis Tools in ArcToolbox are specific to raster data. In the lab exercises we will use many of these tools.

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XtoolsXtools

Third party software, available free www.esri.com (support - downloads)

• Update area after overlay or proximity analysis

• Table frequency (table summations)

• Add XY coordinates to a table

Xtools is a ‘third party software’ available at the ESRI web site. During this course we will use Xtools in three applications

1. Update area after performing and overlay analysis. This is necessary because a clip or intersect operation creates new polygons that may have an area different than the original area of the polygon.

2. Table summations can be performed in Xtools or directly in the tables in ArcMap

3. You can use Xtools to add the numbers for the X and Y coordinates of a point file.

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What is a summary tableWhat is a summary table

Summary table

Attribute table

A polygon attribute table in ArcGIS contains one row for each polygon in the dataset. You are here looking at a polygon layer of land managers on Craig Mountain in Idaho. Commonly a land manager manages more than one polygon on the map. For example the Bureau of Land Management (BLM) manages all the ‘yellow’ areas (polygons) on the map and hence the attribute table contains many rows where the land manager is BLM.

In the summary table all areas managed by the BLM are summarized (expressed in hectares in this example) and the table contains only one line per land manager. A summary table is sometimes called a frequency table.

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Craig Mountain Wildlife Management AreaCraig Mountain Wildlife Management Area

Elevation range: 230-1740 m

Coeur d’AleneMoscowLewiston

Boise

In Exercise 2 and in many of the following exercises in CNR402 you will be working with data from the Craig Mountain Wildlife Management Area.The Craig Mountain Wildlife Management Area is located north of the confluence of the Snake River and the Salmon River in western Idaho. Size: >65,000 ha (About 250 mi2 , 162,000 ac) Elevation ranges from 200-1500 m (750-5000 ft), from the Snake and Salmon Rivers to the forested plateaus with steep, dissected topography.

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The flat top of Craig Mountain is forestedThe flat top of Craig Mountain is forested

Photo: S. Bunting

Many of the datasets we will be working on through this course originates from the Craig Mountain GIS database. The following slides introduce the vegetation and topography of the Craig Mountain Wildlife Management Area.Mixed conifer forests (background) and mountain meadows dominate on the rolling plateaus at the higher elevations. This is stiff sage (Artemisia rigida) in the foreground. Other meadows support grasses and forbs, some are wet. On this flatter ground at higher elevation, many (but not all) of the forests have been logged, and many (but not all) of the meadows have been grazed by cattle. There is less logging and grazing now than in the past.

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Craig Mountain mid elevationsCraig Mountain mid elevations

Photo: S. Bunting

This view is from the top of Corral Creek down toward the Snake River. Forests are more and more interspersed with canyon grasslands as you approach middle elevations.

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North-facing forested slopeNorth-facing forested slope

Photo: S. Bunting

You are looking at a north-facing slope at middle elevation is Corral Creek. Douglas-fir (Pseudotsuga menziesii) and ponderosa pine (Pinus ponderosa) trees grow with diverse shrubs, including ninebark (Physocarpus malvaceous ), oceanspray (Holodiscus discolor), snowberry (Symphoricarpus albus) and rocky mountain maple (Acer glabrum).

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South-facing slopeSouth-facing slope

Photo: S. Bunting

Here is the south-facing slope from the same point as the last slide, at middle elevation is Corral Creek. Much of the same vegetation occurs, but the forests are more open and interspersed with grasslands. Topography (both elevation and aspect) have a tremendous influence on the vegetation composition.

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Flat benches above the riverFlat benches above the river

Photo: S. Bunting

Weeds predominate on the flatter benches, including those far above the river like this one, and those adjacent to the river. All but the smallest, most remote benches were farmed and heavily grazed in the past.

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Yellow starthistle and other exoticsYellow starthistle and other exotics

Photo: S. Bunting

Yellow star thistle (Centaurea solstitialis), an invasive exotic, has largely out-competed and replaced the native perennial grasses here. Weed management is a very challenging issue for the managers of both public and private land in the Craig Mountains. The proportion of native species increases, in general, with elevation. More weeds are found near the roads, areas that were once cultivated and heavily grazed, and at low elevations.

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Low elevation benchesLow elevation benches

Photo: S. Bunting

Continuing downhill to the benches at the lowest elevation, we find even more weeds. The gray vegetation in the background is yellow star thistle. The large plants in the foreground are Scotch thistle (Onopordum acanthium). Both are invasive exotic plants. Most of the grasses in the foreground are also exotic. Here Japanese brome (Bromus japonicus) and cheatgrass (Bromus tectorum) predominate; both are annual grasses that are favored by any disturbance.

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Landsat image July 2000Landsat image July 2000

Landsat 7Path 42 row 28July 27, 2000

Craig Mountain Area

This Landsat image is displayed in ‘false-color infrared’ color combination, that is why the forested areas look red. The green areas are canyon grasslands and the white areas are harvested agricultural fields. There are also some clouds in the lower right of the image.

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Landsat image August 2000Landsat image August 2000

Landsat 7

Path 42 row 28

August 28, 2000

In mid August in year 2000 the southern half of Craig Mountain burned in the Maloney Creek wildfire

In mid August in year 2000 the southern half of Craig Mountain burned in the Maloney Creek wildfire. You can still see the smoke from the Maloney Creek fire and also from other fires burning to the south of the Salmon River.

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Craig Mountain before and after fireCraig Mountain before and after fire

July 27, 2000 August 28, 2000

This is a close-up of the Craig Mountain area before and after the Maloney Creekfire.

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Craig Mountain Cover TypesCraig Mountain Cover Types

Disturbed GrasslandFoothills GrasslandExposed RockDouglas-firMixed Mesic ForestMontane Parkland and MeadowPonderosa PineMesic Upland ShrubHeabaceous ClearcutsWarm Mesic ShrubBroadleaf Dominated RiparianNeedleleaf Dominated RiparianGraminoid or Forb Dominated RiparianShrub Dominated RiparianAgricultureWater

This vegetation data was produced by the Idaho Gap Analysis Project (http://www.wildlife.uidaho.edu/idgap/). It was interpreted from Landsat satellite imagery and has a resolution of 30 m and has been locally ground-referenced.

The thematic accuracy of the data layer is approximately 70% meaning that if you go to any single pixel on the map the chance is 70% that the cover type is actually what is says it is in the map key. .

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GIS Analysis Tasks GIS Analysis Tasks

Existing:Add vector data:

Add raster data:

VegetationRoadsStreamsLand ownershipCounty boundaries

Elevation (later)

1. Create a GIS project for Craig Mountain

2. Apply overlay analysis tools and Xtoolsto the Craig Mountain datasets

In the following lab you will set up a study area project for the Craig Mountain Wildlife Management Area. The vegetation cover type data layer already exists. In lab 2 you will add roads, streams, land ownership and county boundaries to the map. Many of the layers exist as state-wide datasets and you will use the analysis tools in ArcToolbox to clip the layers to the Craig Mountain boundary.In a later lab you will also add a digital elevation model to the Craig Mountain project.In the second part of lab 2 you will practice using a few of the analysis tools in ArcToolbox and also use Xtools.

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GIS Tips!GIS Tips!

• Avoid using folder and file names that includes a space. Rather than naming a folder ‘GIS Data’ name it ‘GISData’ or ‘GIS_Data’

• Use ArcCatalog for management of GIS data (copying, moving, renaming etc.). If you use Windows Explorer for data management you may corrupt or loose GIS data.

• Manage your data well. Keep all data related to a project in the same main folder. This enables you to back up and transfer your entire project to a CD or DVD when finished.

Before starting your next lab I have a few general TIPS to share. If you follow these rules you are more likely to be able to complete the laboratory exercises.

1. Do NOT use spaces in the folder names that contain GIS data. Also avoid using spaces in file names or anything that has to do with GIS.

2. Use ArcCatalog for all data management such as copying, deleting, or moving data sets. If you use Windows Explorer or ‘My Computer’ for data management you may corrupt files.

3. Manage your data well, i.e. keep data in project related folders. This will enable you to easily transfer entire projects to a CD.

Documents

NR402 GIS Applications in Natural Resources€¦ · NR402 - GIS Applications in Natural Resources The flat top of Craig Mountain is forested Photo: S. Bunting Many of the datasets