The world of RASTER The world of RASTER datadata

Modeling... Elevation....etc.Modeling... Elevation....etc.

The Spatial Analyst ExtensionThe Spatial Analyst Extension

Two ways of looking at the Two ways of looking at the world...world...

The vector view...The vector view...

All objects are made up of points, lines All objects are made up of points, lines and polygonsand polygons

All the shape files and coverages are All the shape files and coverages are vector filesvector files

The stained glass window, a vector representation of the world.

The tile mosaic: a raster representation of the world.

The raster view of the world...The raster view of the world... All objects are made up of small cells (often All objects are made up of small cells (often

squares) (this is called a tessellation)squares) (this is called a tessellation) Each grid cell can carry a only single piece Each grid cell can carry a only single piece

of identifying information e.g. elevation or of identifying information e.g. elevation or land cover or soil type or population densityland cover or soil type or population density

Remote sensing data is raster based (the Remote sensing data is raster based (the individual cells are called pixels)individual cells are called pixels)

Computationally simple... Most models are Computationally simple... Most models are raster basedraster based

The raster attribute table...The raster attribute table...

Image DataImage Data

All image data are raster formatAll image data are raster format The cells carry digital number values that The cells carry digital number values that

indicate brightness in a given part of the indicate brightness in a given part of the spectrumspectrum

The Digital Raster Graphics (DRG) fileThe Digital Raster Graphics (DRG) file

The DRG is a scanned USGS topographic map. It is a TIFF file with an associated world file that provides spatial reference information

The TIFF file

The “world” File

The world file must be in the same directory as the image for spatial registration to work. A TIFF world file is *.TFW a Mr. Sid Image world file is *.SDW, the world file for a JPEG is *.JPW...

SO what do these numbers mean?

The transformation parameters are stored in the world file in this order:

20.17541308822119 - A 0.00000000000000 - D 0.00000000000000 - B -20.17541308822119 - E 424178.11472601280548 - C 4313415.90726399607956 - F

A = x-scale; dimension of a pixel in map units in x directionB, D = rotation termsC, F = translation terms; x,y map coordinates of the center of the upper-left pixelE = negative of y-scale; dimension of a pixel in map units in y direction

Note The y-scale (E) is negative because the origins of an image and a geographic coordinate system are different. The origin of an image is located in the upper-left corner, whereas the origin of the map coordinate system is located in the lower-left corner. Row values in the image increase from the origin downward, while y-coordinate values in the map increase from the origin upward.

More Image data....the DOQQMore Image data....the DOQQ

Digital Ortho Quarter Quads (DOQQ)Digital Ortho Quarter Quads (DOQQ) Pan-chromatic aerial photography has Pan-chromatic aerial photography has

been scanned, corrected for tonal been scanned, corrected for tonal differences, referenced to map space, differences, referenced to map space, projected to UTM and made available by projected to UTM and made available by the USGSthe USGS

GeoTIFF format is available.... The spatial GeoTIFF format is available.... The spatial reference information is stored in the TIFF reference information is stored in the TIFF headerheader

The GeoTIFF

Header file

Mr.Sid?Mr.Sid?

What is a SID file?What is a SID file?MrSID is an acronym for Multi-resolution MrSID is an acronym for Multi-resolution Seamless Image Database. MrSID is a powerful Seamless Image Database. MrSID is a powerful wavelet based image compressor, viewer and wavelet based image compressor, viewer and file format for massive raster images that file format for massive raster images that enables instantaneous viewing and manipulation enables instantaneous viewing and manipulation of images locally and over networks while of images locally and over networks while maintaining maximum image quality maintaining maximum image quality

http://magic.lib.uconn.edu/help/faq/faq_sid.htmlhttp://magic.lib.uconn.edu/help/faq/faq_sid.html http://www.lizardtech.com/support/geo/http://www.lizardtech.com/support/geo/

Some places have DOQ data available for download......

A neat trick in arcview.... Go to the legend editor for the DRG.

Choose the colormap and change specified colors to transparent...

Oops! Note the offset...this is diagnostic of a datum shift between NAD 27 and NAD84

A better example of combining DRG with another Image

Finding and using DEM dataFinding and using DEM data

DEM data was developed as an offshoot DEM data was developed as an offshoot of the cruise missile program...of the cruise missile program...

The ‘brain’ of a cruise missile has to be The ‘brain’ of a cruise missile has to be able to ‘see’ the landscape and compare it able to ‘see’ the landscape and compare it to an data set stored in its memory... A to an data set stored in its memory... A digital elevation modeldigital elevation model

Each cell carries elevation data Each cell carries elevation data

Continuous Raster Data: the Digital Elevation Model (DEM)

GIS Data Depot: DEM, DRG of the US.

http://data.geocomm.com/

A variety of data are available: lets look at the processes needed for acquiring and displaying a DEM

The file identifier

Digital Elevation Model

SDTS (spatial data transfer standard): “I’m from the Government and I’m here to help you!”

“TAR”... A UNIX command used to transfer an entire directory to a new location

Gnu Zip... A free compression utility

Virtually all compression/decompression programs e.g. WinZip know how to handle *.TAR.GZ files

The Spatial Data Transfer Standard The Spatial Data Transfer Standard (SDTS)(SDTS)

http://mcmcweb.er.usgs.gov/sdts/whatsdts.htmlhttp://mcmcweb.er.usgs.gov/sdts/whatsdts.html

““The purpose of the SDTS is to promote and The purpose of the SDTS is to promote and facilitate the transfer of digital spatial data facilitate the transfer of digital spatial data between dissimilar computer systems...”between dissimilar computer systems...”

http://thor-f5.er.usgs.gov/sdts/articles/pdf/senmgr.phttp://thor-f5.er.usgs.gov/sdts/articles/pdf/senmgr.pdfdf

The guidebook for “senior managers”... Should The guidebook for “senior managers”... Should come with cartoons and short words .... come with cartoons and short words ....

While there are a variety of SDTS file converters, I prefer SDTS2DEM.exe: as this program is no longer easy to find, I have placed a copy on my web site www2.una.edu/gggaston

SDTS2DEMSDTS2DEM

A simple DOS based executableA simple DOS based executable Must reside in the same directory as the SDTS Must reside in the same directory as the SDTS

filesfiles You CANNOT have ANY spaces in file names or You CANNOT have ANY spaces in file names or

directories!directories! e.g. “My Documents”e.g. “My Documents” Use_the_underscore_character_to_divide_Use_the_underscore_character_to_divide_

file_or_directory_namesfile_or_directory_names

Ready to convert SDTS to a standard USGS DEM format that can be used in the GIS program.

Note the lack of spaces in the path/filenames and the SDTS2DEM program

The first four characters of the base name are numbers

The output is the DEM file that gets written

L0... Just type it...it always works

All these

Have become

this

In Arcview 3.X you must activate the spatial analyst extension

The SDTS2DEM converts the SDTS format to a standard USGS DEM format, it is necessary to then import that file into arcview:

The DEM can now be used in Arcview, a nice trick is to create a hillshade of the data and use it as a brightness theme:

Hypsometric tinting with Shaded relief as brightness theme: