3_2 raster analysis

7/28/2019 3_2 Raster Analysis

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NR 422: Raster Analysis

Jim Graham

Spring 2010
http://jan.ucc.nau.edu/~rcb7/namNm15.jpg


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Continuous vs. Categorized

Continuous: Like photographs

Satellite and aerial photos

Best for analysis Categorized or discrete

Land Cover

Eco-regions Limited analysis

Careful on precision and accuracy


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Categorical vs. Continuous


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No-Data or NULL Values

Rasters arealways

rectangular

No-Data valuesare transparent

and are not used

for calculations


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Geo-Referenced Raster

Known Projection and Datum Width and height of a pixel in map units

(X1,Y1)

Width in Pixels

Height in pixels


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Geo-Referenced Raster

Known Projection and Datum(X1,Y1)

(X3,Y3)


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Types of Rasters

Digital Elevation Model (DEM) Digital Raster Graphic (Topos)

Satellite and Aerial Photos

Land Cover & other naturalcharacteristics

Cost Distance & other economic

Population, taxes, etc.

Your own!


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Digital Raster Graphic


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Digital Elevation Model (DEM)


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Hill-shade


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Contours


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Contours

DEM Cross Section

2000m

1900m

2100m

2200m


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Slope


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Calculating SlopeDEM Cross Section


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Aspect Direction of the slope

Slope

Aspect (Direction)

Angle

Rise

Run

Slope = (Rise/Run) * 100%


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Aspect


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Hill-shade


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Creating a Hillshade

Obtain a DEM Crop to Desired Area

Create Hillshade

Apply color ? To DEM Add DEM over Hillshade with

Transparency


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Screen shots: Hillshade dialog

Colorizing dems

Transparency


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Spatial Analyst Extension

Make sure SpatialAnalyst is Checked


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Tool Bar

Right-click in themenu area

Select Spatial

Analyst


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Hill-shading

Azimuth: Direction ofthe sun relative to the

ground. 0 is north.

Altitude: Angle fromthe horizon to the sun.

North

Azimuth

Altitude

Horizon


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Colorize the DEM


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Make the Hillshade Transparent


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Continuous vs. Categorized

Continuous: Like photographs

Satellite and aerial photos

Best for analysis Categorized or discrete

Land Cover

Eco-regions Limited analysis

Careful on precision and accuracy


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GeoReferenced File Formats

GRID: ESRIs format GeoTIFF: Excellent support

MrSID: LizardTech

IMG: ERDAS ECW: ERMapper

BIL, BIP, BSQ: See header (w/prj)

ASCII or GRID ASCII (w/prj)


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World Files

Contains: X-dimention Pixel size in map units

Y-axis rotation

X-axis rotation Y- dimension Pixel size in map units

(negative)

X-coordinate of upper-left pixel

Y-coordinate of upper-left pixel

Image file contains width and height


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Not Geo-Referenced

BMP PNG

GIF

JPEG Maybe with a world file and prj file?


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JPEG

Joint Photographic Experts Group Widest used photo format

Not for use with vectors

JPEG2000 Completely new format!

Can be georeferenced

Edge of Rocky Mountain National ParkBoundary with high JPEG compression


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Tagged Image File Format

TIFF Can be georeferenced (GeoTIFF)

Can tell in ArcCatalog or ArcMap

TIFF w/world file

Also need Projection and Datum (prj?)

Can be compressed

Run-length Categorical data

LZW Categorical data

Huffman encoding Categorical data

JPEG- Continuous data (dont used on

Categorical data!)


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GRIDS

ESRIs native raster format Pyramids

Not an exchange format!


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ASCII format

NCOLS 10

NROWS 9

XLLCORNER 1000

YLLCORNER 1000

CELLSIZE 1 NODATA_VALUE -9

-9 -9 1 1 0 1 0 1 -9 -9

-9 -9 1 1 2 2 2 1 1 -9 -9 1 1 1 2 2 2 2 3 3

Etc.

See example


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Types of Rasters

Land Cover: forest, grass, water, roads,urban

Digital Elevation Model: DEM

Aerial Photos Satellite Photos

Scanned: DRG, 24k Topos

Derived rasters: lots!


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Derived Rasters

Land Cover from satellite andaerial

Topography: Slope, aspect,

hillshade

Ecoregions

Suitable Habitat

Flood plains

Geological Regions


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Raster To Vector

Satellite & Aerial Land Cover: roads, forests, etc.

Buildings

DEMs Contours

Peaks & Valleys

Stream Networks

Watersheds


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Vector To Raster

Drawing! Points of interest

Roads

Water bodies Contours


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GIS Analysis

Analysis

Results

Raster to

Vector

Vector toRaster


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Raster Analysis

Topography: Slope, aspect, contours Raster Math

Statistics: min, max, mean, std. dev.

Distance Density

Interpolation

Classification

Raster / Vector Conversions


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Raster Math

A matrix of pixels

12 20 23 34 40

15 23 30 31 39

15 22 29 30 40

14 20 28 29 38

13 19 25 32 37

Columns

Rows

S


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Spatial Analyist

A l i E i


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Analysis Environment

Spatial Reference (Coordinate System) Make them the same

Extent

Area of interestAll rasters should overlap

Cell Size

Largest of all rasters or larger

S ti l A l t G l


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Spatial Analyst: General

S ti l A l t E t t


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Spatial Analyst: Extent

S ti l A l t C ll Si


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Spatial Analyst: Cell Size

R t C l l t


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Raster Calculator

R t M th


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Raster Math

1 2

2 3

12 9

13 10

13 11

15 13+ =

+ =1 12 13

C F ti


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Common Functions

Local:Arithmatic: +,-,/, *,

MOD (Modulo): returns the remainder

Boolean:

OR: If either input is true, output is true

AND: If both inputs are true, output is true

CON (Conditional)

M th ti l F ti


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Mathematical Functions

Abs (absolute): flips negatives to positive Ceil (ceiling): float to integer next highest

integer value (i.e. 1.1 -> 2)

Floor: float to integer giving next lowestinteger value (i.e. 1.1 -> 1)

Int (integer): truncates float to integer

E t


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Exponents

Exp()

Exp10()

Ln()

Log10()

Max() Min()

Pow()

SetNull() Sqrt()

Sum()

C i


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Comparisons

(Not Equals) == (Equals)

< (Less than)

(Greater than)

>= (Greater than or equal to)

R t M th C i


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Raster Math: Comparisons

1 2

2 3

2 2

3 2

0 0

0 1> =

> =1 2 0

R t M th B l AND


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Raster Math: Boolean AND

0 0

1 1

0 1

0 1

0 0

0 1AND =

AND =0 1 0

AND works but the calculator will insert &

Raster Math Boolean OR


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Raster Math: Boolean OR

0 0

0 1

1 1

0 1

1 1

0 1OR =

OR =0 1 1

OR works but the calculator will insert !

Conditional Operator


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Conditional Operator

Con(,,) Given a raster condition:

Puts the true value where true and false

value where false

Example:

Find the elevations in Rocky over 3000

meters

HighElevations=con(RockyDEM>3000,1,0)

Elevations over 3000 meters


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Viewshed


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Viewshed

Shows which pixels can be seen frompre-defined locations

View shed


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View-shed

View from Estes Park


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View from Estes Park

View from Ridge


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View from Ridge

3_2 raster analysis

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